DEPARTMENT OFELECTRONICS AND COMMUNICATION ENGINEERING EC1020 COMMUNICATION ENGINEERING LABORATORY MANUAL FACULTY OF ENGINEERING AND TECHNOLOGY SRM UNIVERISTY S.R.M. NAGAR, KATTANKULATHUR – 603203. KANCHEEPURAM DISTRICT DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING EC1020 Communication Engineering Lab Laboratory Manual Course Team Mr.S.Bashyam Mrs. G. Kalaimagal Mr.M.Aravindan Mrs. M. NeelaveniAmmal Mrs. S. Sudarvizhi Mrs.S.Kolangiammal Mrs. S. VasanthadevSuryakala Mrs.G.Suganthibrindha Mrs. P. Malarvezhi Mrs. S. Krithiga Mr. G. ElavelVisuvanathan June 2015 Revision: 00 SYLLABUS OF EC1020 COMMUNICATION ENGINEERING LAB Course Number and Title EC1020 COMMUNICATION ENGINEERING LAB
Credits / Contact Hours 2/45 Instructor Name
Mrs. S. Kolangiammal Textbooks, References • John O. Attia, “PSPICE and MATLAB for Electronics: An integrated approach”, CRC press, 2002. • LAB MANUAL, Department of ECE, SRM University. Purpose The experiments in this laboratory enable the students to gather basic knowledge on communication systems. Different experiments are performed which forms the fundamental blocks of any communication system used now‐a‐days. Experiments are performed using electronic instrument, such as oscilloscopes, signal generators, spectrum analyzers, and network analyzers. Certain experiments are simulated using MATLAB and P‐SPICE simulation software. Prerequisites Nil Required, Elective orSelected Elective (as per Table 5.1a)
Co‐requisites EC1018
Required
Instructional Objectives 1. To practice the basic theories of analog communication system. 2. To provide hands‐on experience to the students, so that they are able to apply theoretical concepts in practice. 3. To use computer simulation tools such as P‐SPICE, or MATLAB to carry out design experiments as it is a key analysis tool of engineering design. 4. To give a specific design problem to the students, which after completion they will verify using the simulation software or hardware implementation. Student Outcomes from Criterion 3 covered by this Course
Student Outcome
a
Mapping of instructional objectives with student outcome b
C
d
e
f
X
X
X
X
1‐4
1‐4
1‐
4 1‐4
g
h i j k
X
X X X
3,4
3,4 4 3,4
List of Topics Covered 1. AM modulator and Demodulator. 2. DSB‐SC modulator and Demodulator. 3. SSB Modulation and Demodulation in MATLAB. 4. FM modulator and Demodulator. 5. PAM modulator and Demodulator. 6. TDM Multiplexer and Demultiplexer. 7. FDM Multiplexer and Demultiplexer. 8. Pre emphasis and De‐emphasis in FM. 9. Simulation experiments using P‐SPICE and MATLAB. a) AM modulator with AWGN noise in MATLAB. b) Pre‐emphasis and De‐emphasis in FM using P‐SPICE. S.R.M University Faculty of Engineering and Technology Department of Electronics and Communication Engineering Sub Code : Sub Title : Pre‐ requisite : Co‐ requisite : EC1020 Semester : V Communication Engineering Lab Course Time : Jun‐Dec ‘15 NIL EC1018 COMMUNICATION THEORY Program Outcome b. Graduate will demonstrate the ability to identify, formulate and solve engineering problems Experiment 1: AM modulation and demodulation Experiment 2: Frequency modulation c. Graduate will demonstrate the ability to design and conduct experiments, analyse and interpret data. Experiment 1: Amplitude modulation and demodulatation Experiment 2: Frequency Modulation Experiment 3: PAM modulation and Demodulation Experiment 5: Pre‐emphasis and De‐emphasis in FM d.Graduates will demonstrate the ability to design a system, component or process as per needs and specifications Experiment 6: Amplitude Modulation with AWGN noise in MATLAB Experiment 7: Pre‐emphasis and De‐emphasis using PSPICE e.Graduates will demonstrate the ability to visualize and work on laboratory and multi‐
disciplinary tasks. Experiment 1: Amplitude modulation and demodulation Experiment 2: Frequency Modulation Experiment 3: PAM modulation and Demodulation Experiment 5: Pre‐emphasis and De‐emphasis in FM f. Graduate will demonstrate the skills to use modern engineering tools, software’s and equipment to analyse problems. Experiment 6: Amplitude Modulator with AWGN noise in MATLAB Experiment 7: Pre‐emphasis and De‐emphasis using PSPICE Experiment 8:FM Modulation in MATLAB Experiment 9:DSB‐SC modulation in MATLAB Experiment 10:SSB‐SC Modulation and demodulation in MATLAB i.Graduate will show the understanding of impact of engineering solutions on the society and also will be aware of contemporary issues. Experiment 6: Amplitude Modulator with AWGN noise in MATLAB Experiment 7: Pre‐emphasis and De‐emphasis using PSPICE Experiment 8:FM Modulation in MATLAB Experiment 9: DSB‐SC modulation in MATLAB Experiment 10: SSB‐SC Modulation and demodulation in MATLAB j. Graduate will develop confidence for self education and ability for life‐long learning. Experiment 6: Amplitude Modulator with AWGN noise in MATLAB Experiment 7: Pre‐emphasis and De‐emphasis using PSPICE Experiment 8: FM Modulation in MATLAB Experiment 9: DSB‐SC modulation in MATLAB Experiment 10: SSB‐SC Modulation and demodulation in MATLAB k. Graduate will show the ability to participate and try to succeed in competitive examinations Experiment 6: Amplitude Modulator with AWGN noise in MATLAB Experiment 7: Pre‐emphasis and De‐emphasis using PSPICE Experiment 8: FM Modulation in MATLAB Experiment 9: DSB‐SC modulation in MATLAB Experiment 10: SSB‐SC Modulation and demodulation in MATLAB S.R.M University Faculty of Engineering and Technology Department of Electronics and Communication Engineering Sub Code : EC1020 Semester : V Sub Title : Communication Engineering Lab Course Time : Jun‐Dec ‘15 Pre‐ requisite : NIL Co‐ requisite : EC1018 COMMUNICATION THEORY S. No. Experiments Detail Equipments/Software Required 1 AM Modulator and demodulator Regulated power supply,CRO, AFO 2 FM modulator Regulated power supply,CRO, AFO 3 PAM modulator and Demodulator AFO, CRO 4 TDM Multiplexer and De‐
multiplexer Using Trainer TDM‐TRAINER KIT,CRO Kit 5 Pre‐emphasis and De‐
emphasis in FM 6 7 8 9 10 AM modulator with AWGN noise in MATLAB. Pre‐emphasis and De‐
emphasis in FM using P‐
SPICE. FM modulation in MATLAB DSB‐SC modulation in MATLAB SSB –SC modulation and Demodulation in MATLAB Components Required Resistors, capacitors Semiconductors: BC108,OA79 Resistors: As per design Capacitors: As per design Semiconductors: IC NE 566 Resistors: As per design Capacitors: As per design Semiconductors: BC107 ‐ Resistors: As per design Regulated power Capacitors: 0.1µF, 0.01µF supply AFO, CRO, Decade Inductance box. Semiconductors: Q2N2222 MATLAB. ‐ P‐SPICE ‐ MATLAB ‐ MATLAB ‐ MATLAB ‐ S.R.M University Faculty of Engineering and Technology Department of Electronics and Communication Engineering Sub Code : Sub Title : Pre‐ requisite : Co‐ requisite : EC1020 Semester : V Communication Engineering Lab Course Time : Jun‐Dec ‘15 NIL EC1018 COMMUNICATION THEORY Program Educational Objective Student Outcomes PEO1: PEO2:
PEO3:
PEO4:
Graduates will perform as a successful Professional engineer in related fields of Electronics and Communication Engineering. Graduates will pursue higher education and/or engage themselves in continuous professional development to meet global standards. Graduates will work as a team in diverse fields and gradually move into leadership positions. Graduates will understand current professional issues, apply latest technologies and come out with innovative solutions for the betterment of the nation and society. √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ b c d e f i j k √ √ √ Academic Course Description SRM University
Faculty of Engineering and Technology Department of Electronics and Communication Engineering EC1020 Communication Engineering Laboratory Fifth Semester, 2015‐16 (OddSemester) Course (catalog) description This course provides the foundation education in communication engineering lab. The experiments in this laboratory enable the students to gather basic knowledge on communication systems. Different experiments are performed which forms the fundamental blocks of any communication system used now a day. Experiments are performed using electronic instrument, such as oscilloscopes, signal generators, spectrum analyzers, and network analyzers. Certain experiments are simulated using MATLAB and P‐SPICE simulation software. Compulsory/Elective course: Compulsory Credit hours: 2 credits Laboratory Communication EngineeringLaboratory (TP10L4) , Computing Laboratory (TP10L1), RF Laboratory (TP13L4) Course coordinator(s) S.Kolangiammal, Assistant Professor (Ordinary Grade), Department of ECE INSTRUCTOR(S) Email Class Office Office (@ktr.srmuniv.ac.i Consultations
handling location phone
n) Day 4‐12.45PM Mr. S. Bashyam X1 TP103A 2075 bashyam.s to 1.20PM TP1103
Day 3‐12.45PM Mrs Kalaimagal X2 2062 Kalaimagal.g A to 1.20PM TP1103
Day 1‐12.45PM Mr.M.Aravindan X3 2063 Aravindan.m A to 1.20PM Mrs. M. Day 5‐12.45PM X4 TP12S4 2087 Neelaveniammal.m NeelaveniAmmal to 1.20PM . TP1003
Day 5‐12.45PM Ms. S. Sudarvizhi X5 2059 sudarvizhi.s A to 1.20PM . Mrs.S.Kolangiamm
TP1003
Day 5‐12.45PM Y1 2059 kolangiammal.s al A to 1.20PM Mrs.S.Vasanthadev
TP1003
vasanthadevsuryak Day 5‐12.45PM Y2 2059 Suryakala A ala.s to 1.20PM . Mrs.G.Suganthi Day 1‐12.45PM Y3 TP10S8
‐ Suganthibrindha.g brindha to 1.20PM . TP1203
Day 1‐12.45PM Mrs. P. Malarvizhi Y4 2064 malarvizhi.p A to 1.20PM . TP1203
Day 1‐12.45PM Mrs. S. Krithiga Y5 2064 Krithiga.s A to 1.20PM . Mr. G. Elavel ElavelVisuvanathan Day 5‐12.45PM Y6 TP10S4
‐ Visuvanathan .g to 1.20PM . Name of the instructor RELATIONSHIP TO OTHER COURSES Pre‐requisites : Assumed knowledge : Following courses : NIL BJT – Basic device operation and characteristics Signal generators – sinusoidal and non‐sinusoidal generators EC1025 Digital communication lab Text book(s) and/or required materials: Lab manual; additional materials posted on SRM web. References 1. Communication Engineering Lab MANUAL, Department of ECE, SRM University 2. John O Atta “PSPICE AND MATLAB for electronics: AN Integrated approach”, CRC press 2002 Computer usage To carry out AM and Pre emphasis and deemphasis experiments using discrete electronic components, Software’s like MATLAB and PSPICE are used to simulate the circuit operations Hardware Laboratory Usage Each laboratory station is equipped with breadboards, a power supply, CRO and Function generators. Students work in groups of three, but maintain individual laboratory notebooks and submit individual records. Class / Lab schedule : one 100 minutes lab session per week, for 10‐14 weeks Group X1 X2 X3 X4 X5 Y1 Y2 Y3 Y4 Y5 Y6 Schedule DAY 1 – 7, 8 & DAY 2 ‐ 3,4 DAY 3 – 7, 8 & DAY 4 ‐ 7,8 DAY 3 – 7, 8 & DAY 5 ‐ 3,4 DAY 2 – 3, 4 & DAY 3 ‐ 7,8 DAY 2 – 3, 4 & DAY 5 ‐ 7,8 DAY 2 – 7, 8 & DAY 5 ‐ 3,4 DAY 2 – 7, 8 & DAY 3 ‐ 3,4 DAY 3 – 3, 4 & DAY 4 ‐ 7,8 DAY 3 – 3, 4 & DAY 5 ‐ 7,8 DAY 4 – 7, 8 & DAY 5 ‐ 3,4 DAY 1 – 7, 8 & DAY 4 ‐ 1,2 Professional component General Basic Sciences Engineering sciences & Technical arts Professional subject ‐ ‐ ‐ ‐ 0% 0% 0% 100% Broad area: Communication | Signal Processing | Electronics | VLSI | Embedded Mapping of Instructional Objectives with Program Outcome This course provides the foundation education in Correlates to Student communication systems. Through lecture, laboratory, and Outcome out‐of‐class assignments, students are provided learning H M L
experiences that enable them to: 1.To practice the basic theories of analog communication b,c,d,e I,j,k system. 2. To provide hands‐on experience to the students, so that they are b,c,d,e,f,I,k j able to apply theoretical concepts in practice. 3.To use computer simulation tools such as P‐SPICE, or Matlab to b,c.d,e.f.i,j,,k carry out design experiments as it is a key analysis tool of engineering design. 4.To give a specific design problem to the students, which after completion they will verify using the simulation software or b,c,d,i e,f,j,k hardware implementation H: High correlation, M: Medium correlation, L: Low correlation COURSE TOPICS S.No. Lab Experiments Sessions Using discrete components and/or BC107/BC108/Q2N2222/IC566 1 AM modulation and Demodulation. 1 2 FM modulation 2 3 PAM modulation and Demodulation. 3 4 TDM Multiplexer and Demultiplexer Using Trainer Kit 4 5 Pre emphasis and De‐emphasis in FM. 5 Simulation experiments using MATLAB& P‐SPICE. 6 AM modulator with AWGN noise in MATLAB. 6 7 Pre‐emphasis and De‐emphasis in FM using P‐SPICE. 7 8 FM Modulation in MATLAB 8 9 DSB‐SC modulation in MATLAB 9 10 SSB modulation and Demodulation in MATLAB 10 Mapping of Instructional Objective with experiments: List of Experiments IO#1 IO#2 AM modulation and Demodulation. X X FM modulation X X PAM modulation and Demodulation. X X TDM Multiplexer andDemultiplexer Using X X Trainer Kit Pre emphasis and De‐emphasis in FM. X X AM modulator with AWGN noise in X X Matlab. Pre‐emphasis and De‐emphasis in FM X X using P‐SPICE. IO#3 IO#4 X X X X X X X X FM Modulation in MATLAB X X X X DSB‐SC modulation in MATLAB
X X X X SSB modulatIion and Demodulation in MATLAB X X X X EVALUATION METHODS Internal Assessment Marks: 60 Carrying out lab work & Report Mini Project Attendance Model Exam Prepared by: : 30 : : : 5 05 20 End Semester Examination Marks: 40 Circuit diagram / Program : 10 Design / Calculation : 05 Procedure/Algorithm : 05 Tabulation / Graph : 10 Result : 05 Viva‐Voce : 05 Mrs.S.Kolangiammal, Assistant Professor (OG), Department of ECE Dated: 26 june 2015 Revision No.: 00 Date of revision: NA Revised by: NA LABORATORY POLICIES AND REPORT FORMAT Reports are due at the beginning of the lab period. The reports are intended to be a complete documentation of the work done in preparation for and during the lab. The report should be complete so that someone else familiar with electronic design could use it to verify your work. The prelab and postlab report format is as follows: 1. A neat thorough prelab must be presented to your faculty Incharge at the beginning of your scheduled lab period. Lab reports should be submitted on A4 paper. Your report is a professional presentation of your work in the lab. Neatness, organization, and completeness will be rewarded. Points will be deducted for any part that is not clear. 2. In this laboratory students will work in teams of three. However, the lab reports will be written individually. Please use the following format for your lab reports. a. Cover Page: Include your name, Subject Code, Section No., Experiment No. and Date. b. Objectives: Enumerate 3 or 4 of the topics that you think the lab will teach you. DO NOT REPEAT the wording in the lab manual procedures. There should be one or two sentences per objective. Remember, you should write about what you will learn, not what you will do. c. Design: This part contains all the steps required to arrive at your final circuit. This should include diagrams, tables, equations, explanations, etc. Be sure to reproduce any tables you completed for the lab. This section should also include a clear written description of your design process. Simply including a circuit schematic is not sufficient. d. Questions: Specific questions (Prelab and Postlab) asked in the lab should be answered here. Retype the questions presented in the lab and then formally answer them. 3. Your work must be original and prepared independently. However, if you need any guidance or have any questions or problems, please do not hesitate to approach your faculty incharge during office hours. Copying any prelab/postlab will result in a grade of 0. The incident will be formally reported to the University and the students should follow the dress code in the Lab session. 4. Each laboratory exercise (circuit) must be completed and demonstrated to your faculty Incharge in order to receive working circuit credit. This is the procedure to follow: a. Circuit works: If the circuit works during the lab period (3 hours), call your faculty incharge, and he/she will sign and date it.. This is the end of this lab, and you will get a complete grade for this portion of the lab. b. Circuit does not work: If the circuit does not work, you must make use of the open times for the lab room to complete your circuit. When your circuit is ready, contact your faculty incharge to set up a time when the two of you can meet to check your circuit. 5. Attendance at your regularly scheduled lab period is required. An unexpected absence will result in loss of credit for your lab. If for valid reason a student misses a lab, or makes a reasonable request in advance of the class meeting, it is permissible for the student to do the lab in a different section later in the week if approved by the faculty incharge of both the sections. Habitually late students (i.e., students late more than 15 minutes more than once) will receive 10 point reductions in their grades for each occurrence following the first. Student attendance less than 75% is detention. 6. Final grade in this course will be based on laboratory assignments. All labs have an equal weight in the final grade. Grading will be based on pre‐lab work, laboratory reports, post‐lab and in‐lab performance (i.e., completing lab, answering laboratory related questions, etc.,).The faculty Incharge will ask pertinent questions to individual members of a team at random. Labs will be graded as per the following grading policy: Attendance ‐ 05% Lab Performance ‐ 10% Prelab ‐ 05% Post Lab ‐ 05% Report ‐ 10% ‐ 05% Student Contribution Model Exam ‐ 20% Final exam ‐ 40% 7. Reports Due Dates: Reports are due one week after completion of the corresponding lab. 8. Systems of Tests: Regular laboratory class work over the full semester will carry a weightage of 60%. The remaining 40% weightage will be given by conducting an end semester practical examination for every individual student if possible or by conducting a 1 to 1 ½ hours duration common written test for all students, based on all the experiment carried out in the semester. General Procedures a) Properlyplace the components in the breadboard as per circuit diagram, and identify the different input and outputs of the circuit before making connection. b) Know the biasing voltage required for different devices and connect power supply voltage. c) Note down the readings obtained from the CRO or Measuring devices in the observation book. d) Plot the graph on a linear graph or semi log graph and verify its characteristics using model graph. e) After the completion of the experiments switch off the power supply and return the components. ADDENDUM Student Outcomes ofB.Tech ECE program: (a) an ability to apply knowledge of mathematics, science, and engineering (b) an ability to design and conduct experiments, as well as to analyze and interpret data (c) an ability to design a system, component, or process to meet desired needs within realistic constraints such as economic, environmental, social, political, ethical, health and safety, manufacturability, and sustainability (d) an ability to function on multidisciplinary teams (e) an ability to identify, formulate, and solve engineering problems (f) an understanding of professional and ethical responsibility (g) an ability to communicate effectively (h) the broad education necessary to understand the impact of engineering solutions in a global, economic, environmental, and societal context (i) a recognition of the need for, and an ability to engage in life‐long learning (j) a knowledge of contemporary issues (k) an ability to use the techniques, skills, and modern engineering tools necessary for engineering practice. Program Educational Objectives PEO1: Graduates will perform as a successful professional engineer in related fields of Electronics and Communication Engineering. PEO2: Graduates will pursue higher education and/or engage themselves in continuous professional development to meet global standards. PEO3: Graduates will work as a team in diverse fields and gradually move into leadership positions. PEO4: Graduates will understand current professional issues, apply latest technologies and come out with innovative solutions for the betterment of the nation and society. ATTESTATION FROM COURSE TEACHERS NAME OF THE INSTRUCTOR
SIGNATURE Mr. S. Bashyam
Mrs Kalaimagal Mr.M.Aravindan Mrs. M. NeelaveniAmmal Ms. S. Sudarvizhi Mrs.S.Kolangiammal Mrs.S.VasanthadevSuryakala Mrs.G.Suganthibrindha Mrs. P. Malarvizhi Mrs. S. Krithiga Mr. G. ElavelVisuvanathan Course Coordinator Academic Coordinator Professor In‐Charge HOD/ECE (S.Kolangiammal) (Mrs.N. Saraswathy) (Dr.B. Ramachandran) (Dr.S. Malarvizhi) PREFACE The EC1020 Communication Engineering Lab is designed to help students understand the basic principles of communication techniques as well as giving them the insight on design, simulation and hardware implementation of circuits. The main aim is to provide hands‐on experience to the students so that they are able to put theoretical concepts to practice. The content of this course consists of two parts, ‘simulation’ and ‘hardwired’. Computer simulation is stressed upon as it is a key analysis tool of engineering design. “OrCADPspice” and MATLAB software is used for simulation of communication experiments Students will carry out design experiments as a part of the experiments list provided in this lab manual. Students will be given a specific design problem, which after completion they will verify using the simulation software or hardwired implementation. LIST OF EXPERIMENTS Exp. No Title 1 AM modulation and Demodulation. 2 FM modulation 3 PAM modulation and Demodulation 4 TDM Multiplexer and Demultiplexer using trainer kit 5 Pre emphasis and De‐emphasis in FM. 6 AM modulator with AWGN noise in MATLAB. 7 Pre‐emphasis and De‐emphasis in FM using P‐SPICE. 8 FM Modulation in MATLAB 9 DSB‐SC Modulation in MATLAB 10 SSB‐SC modulation and Demodulation in MATLAB LABORATORY ORIENTATION I. OVERALL PURPOSE The laboratory portion of this course is designed to give the student practical experience in working with operational amplifiers. The laboratory integrate the theory taught in the lectures with practical design, and should help the student to apply his or her knowledge of analog electronics. II. GENERAL COMMENTS Every week before lab, each student should read over the laboratory design or experiment and work out the various calculations, etc. that are outlined. The student should refer to the text as prescribed in the course description for the fundamental theory. Your grade will reflect how well you have prepared for the lab. III LABORATORY AND EQUIPMENT MAINTENANCE is the responsibility of not only the laboratory staff, but also the students. A concerted effort to keep the equipment in excellent condition and the working environment well‐organized will result in a productive and safe laboratory. There are useful guides one should follow to avoid the pitfalls in electronic instrumentation and measurement. Above all, keep in mind that safety is first! IV. LABORATORY NOTEBOOK Each student should maintain a laboratory notebook according to the following guidelines: 1.
Obtain a printed material whose pages are consecutively numbered. 2.
Write name, register number, course number and name, section number, lab location, semester, and staff’s name on the cover. 3.
Record data by pen, not pencil. Do not use eraser. 4.
Sign and date each page that has data. 5.
Log all events, whether positive or negative, in the lab. This includes not only data, but also problems encountered, equipment use, equipment settings, measurement technique, or any departure from the procedure suggested by the lab manual. 6.
Record instruments, their settings, and methods used to acquire data. 7.
Label the axes of a graph with variable names, units, origin, and scales. 8.
Demonstrate to the lab staff your understanding and achievement of the lab objectives. 9.
Have the lab staff sign and date all data groups before completing each laboratory session. It is the responsibility of both the staff and the student to make sure that the data is within expectation before the student leaves each lab session. V. PRE‐LAB WORK There are pre‐lab works for each experiment. The prework must be completed in the logbook before entering the laboratory. The prework usually consists of some questions that is closely related to the experimental work and is intended to prepare you for the lab. The labs are designed so that a student who has done the prework should be able to complete the lab in the allotted time. If you find that you are having difficulties completing labs then it is probably a good idea for you to do all of the theoretical work (in addition to the assigned prework) for the experiment before entering the lab. To ensure that you can complete the experimental tasks within the allocated lab session, you could collect all the parts and components from the Lab stores and build the circuits on breadboards before starting the actual lab. Therefore you have more time on testing in the lab session. VI. LABORATORY REPORTS Lab reports will be submitted by each student at the beginning of the following lab period. The report will be graded on clarity, legibility, and content, neither on length nor on the quality of the artwork. Although the data is measured jointly, the text and analysis of the report must be original work and may not be copied. REPORT FORMAT: TITLE PAGE: EXPERIMENT # EXPERIMENT NAME DATE REPORT CONTENT: I. OBJECTIVES (5 sentences max.) II. EQUIPMENT (1 paragraph max.) ‐ include pertinent theory for experiment III. DESIGN IV. EXPERIMENT ‐ include schematic of all circuits built ‐ include names and values of all components actually used ‐ include all data recorded (tables, plots, printouts, observations) V. POSTLAB QUESTIONS ‐ answer all the questions in the postlab component available at the end of each experiment in the laboratory manual. ‐ thepostlab questions are closely related to the experimental work you had done in the lab. VI. SUMMARY VII. EQUIPMENT AND LABORATORY MAINTENANCE Be responsible for equipment and laboratory maintenance. For example: 1. Keep the lab and benches neat and organized. 2. Use the equipment properly. For example, use only the probes that have been compensated for your oscilloscope with your oscilloscope. An oscilloscope and its matched probes are labeled by the same number to help you keep using them together. Do not take the sleeve off the sensitive probe tip and use the probe tip directly (e.g., by inserting the probe tip directly into a hole on a breadboard). Many probes have been permanently damaged when used this way because a) the fragile tip is broken by the severe probing strain, b) the probe accidentally falls to the ground, breaking the fragile tip, or c) the probe sleeve is lost after it is removed from the probe tip. A short hook‐up wire hooked to the probe will allow fine probing without using the probe tip directly. 3. Return instruments, manuals, tools, components, cables, etc., to the proper storage location. 4. Bring defective equipment to the lab staff or laboratory maintenance staff for repair. 5. Notify the lab staff when the stock is about to run out of a certain component. VIII. USEFUL LABORATORY PRACTICES In general, keep the following points in mind: 1. Identify lab objectives. An experiment should not be treated as a cookbook procedure. Find a rationale behind each step. 2. Come to the lab prepared. Preview the experiment as homework. 3. Keep a lab notebook to record all activities during all lab sessions. 4. Finish as much as possible before leaving. This includes acquiring data, interpreting data, answering questions, and revolving uncertainties. 5. All data are real. If data look unbelievable, check all the steps carefully. Consult the lab staff. 6. Safety is first. Change instrument settings slowly. Observe the effect of the most recent change before proceeding with more change. Set voltage/current/power limit. It is important that right from the beginning of your lab work you consider the possible interactions between measuring instruments and the device under test. For example: 7. The input impedance of meters can cause measurement error in high impedance circuits. 8. The input capacitance of scopes, scope probes, or connecting cables may have important high frequency loading effects. 9. When using an oscilloscope to make accurate waveform or frequency response measurements with a x10 probe, make sure the probe is properly compensated. 10. Learn to use the current limiting features of the laboratory power supplies to protest the device under test from possible damage under short circuit conditions. 11. Make sure to have low impedance ground connections between the test instruments and your “breadboard”. Avoid groundloops! The list could go on much longer. It represents the pitfalls of doing electronics in the real world. IX. SAFETY PRECAUTIONS AND LABORATORY RULES To be responsible for your own safety and keep the laboratory in a good order, you must comply with the rules below. ƒ
Solid footwear must be worn by all students inside the laboratory. Staffs are required by the university to ensure that everyone in the laboratory is wearing solid footwear. Students with bare feet, thongs, sandals, or other forms of open footwear will not be allowed into the laboratory. ƒ
No smoking, drinking, or eating is permitted in the laboratory (this includes chewing gum and confectionaries). ƒ
Always have your circuits checked by a demonstrator before switching on, and always switch the power off immediately after taking measurements. ƒ
Act sensibly and tidy up after yourself. ƒ
/There is a safety switch on each bench which switches power to (and protects) the GPO's (general purpose outlets/power points). ƒ
Under no circumstances should you attempt to remove any of the panels on the bench. There is a 220 volt supply behind them which could be lethal. ƒ
You should not take equipment from another bench. If something is faulty (or missing) ask the lab staff for assistance. SAFETY Safety in the electrical laboratory, as everywhere else, is a matter of the knowledge of potential hazards, following safety precautions, and common sense. Observing safety precautionsare important due to pronounced hazards in any electrical/computer engineering laboratory. Death is usually certain when 0.1 ampere or more flows through the head or upper thorax and have been fatal to persons with coronary conditions. The current depends on body resistance, the resistance between body and ground, and the voltage source. If the skin is wet, the heart is weak, the body contact with ground is large and direct, then 40 volts could be fatal. Therefore, never take a chance on "low" voltage. When working in a laboratory, injuries such as burns, broken bones, sprains, or damage to eyes are possible and precautions must be taken to avoid these as well as the much less common fatal electrical shock. Make sure that you have handy emergency phone numbers to call for assistance if necessary. If any safety questions arise, consult the lab demonstrator or technical assistant/technician for guidance and instructions. Observing proper safety precautions is important when working in the laboratory to prevent harm to yourself or others. The most common hazard is the electric shock which can be fatal if one is not careful. ELECTRIC SHOCK Shock is caused by passing an electric current through the human body. The severity depends mainly on the amount of current and is less function of the applied voltage. The threshold of electric shock is about 1 mA which usually gives an unpleasant tingling. For currents above 10 mA, severe muscle pain occurs and the victim can't let go of the conductor due to muscle spasm. Current between 100 mA and 200 mA (50 Hz AC) causes ventricular fibrillation of the heart and is most likely to be lethal. What is the voltage required for a fatal current to flow? This depends on the skin resistance. Wet skin can have a resistance as low as 150 Ohm and dry skin may have a resistance of 15 kOhm. Arms and legs have a resistance of about 100 Ohm and the trunk 200 Ohm. This implies that 240 V can cause about 500 mA to flow in the body if the skin is wet and thus be fatal. In addition skin resistance falls quickly at the point of contact, so it is important to break the contact as quickly as possible to prevent the current from rising to lethal levels. EQUIPMENT GROUNDING Grounding is very important. Improper grounding can be the source of errors, noise and a lot of trouble. Here we will focus on equipment grounding as a protection against electrical shocks. Electric instruments and appliances have equipments casings that are electrically insulated from the wires that carry the power. The isolation is provided by the insulation of the wires. However, if the wire insulation gets damaged and makes contact to the casing, the casing will be at the high voltage supplied by the wires. If the user touches the instrument he or she will feel the high voltage. If, while standing on a wet floor, a user simultaneously comes in contact with the instrument case and a pipe or faucet connected to ground, a sizable current can flow through him or her. However, if the case is connected to the ground by use of a third (ground) wire; the current will flow from the hot wire directly to the ground and bypass the user. Equipment with a three wire cord is thus much safer to use. The ground wire (3rd wire) which is connected to metal case is also connected to the earth ground (usually a pipe or bar in the ground) through the wall plug outlet. Always observe the following safety precautions when working in the laboratory: 1. Do not work alone while working with high voltages or on energized electrical equipment or electrically operated machinery like a drill. 2. Power must be switched off whenever an experiment or project is being assembled, disassembled, or modified. Discharge any high voltage points to grounds with a well‐insulated jumper. 3. Remember that capacitors can store dangerous quantities of energy. 4. Make measurements on live circuits or discharge capacitors with well insulated probes keeping one hand behind your back or in your pocket. Do not allow any part of your body to contact any part of the circuit or equipment connected to the circuit. 5. After switching power off, discharge any capacitors that were in the circuit. Do not trust supposedly discharged capacitors. Certain types of capacitors can build up a residual charge after being discharged. Use a shorting bar across the capacitor, and keep it connected until ready for use. If you use electrolytic capacitors, do not: ƒ
put excessive voltage across them ƒ
put ac across them ƒ
connect them in reverse polarity 6. Take extreme care when using tools that can cause short circuits if accidental contact is made to other circuit elements. Only tools with insulated handles should be used. 7. If a person comes in contact with a high voltage, immediately shut off power. Do not attempt to remove a person in contact with a high voltage unless you are insulated from them. If the victim is not breathing, apply CPR immediately continuing until he/she is revived, and have someone dial emergency numbers for assistance. 8. Check wire current carrying capacity if you will be using high currents. Also make sure your leads are rated to withstand the voltages you are using. This includes instrument leads. 9. Avoid simultaneous touching of any metal chassis used as an enclosure for your circuits and any pipes in the laboratory that may make contact with the earth, such as a water pipe. Use a floating voltmeter to measure the voltage from ground to the chassis to see if a hazardous potential difference exists. 10. Make sure that the lab instruments are at ground potential by using the ground terminal supplied on the instrument. Never handle wet, damp, or ungrounded electrical equipment. 11. Never touch electrical equipment while standing on a damp or metal floor. 12. Wearing a ring or watch can be hazardous in an electrical lab since such items make good electrodes for the human body. 13. When using rotating machinery, place neckties or necklaces inside your shirt or, better yet, remove them. 14. Never open field circuits of D‐C motors because the resulting dangerously high speeds may cause a "mechanical explosion". 15. Keep your eyes away from arcing points. High intensity arcs may seriously impair your vision or a shower of molten copper may cause permanent eye injury. 16. Never operate the black circuit breakers on the main and branch circuit panels. 17. In an emergency all power in the laboratory can be switched off by depressing the large red button on the main breaker panel. Locate it. It is to be used for emergencies only. 18. Chairs and stools should be kept under benches when not in use. Sit upright on chairs or stools keeping the feet on the floor. Be alert for wet floors near the stools. 19. Horseplay, running, or practical jokes must not occur in the laboratory. 20. Never use water on an electrical fire. If possible switch power off, then use CO2 or a dry type fire extinguisher. Locate extinguishers and read operating instructions before an emergency occurs. 21. Never plunge for a falling part of a live circuit such as leads or measuring equipment. 22. Never touch even one wire of a circuit; it may be hot. 23. Avoid heat dissipating surfaces of high wattage resistors and loads because they can cause severe burns. 24. Keep clear of rotating machinery. Precautionary steps before starting an experiment so as not to waste time allocated a) Read materials related to experiment beforehand as preparation for pre‐lab quiz and experimental calculation. b) Make sure that apparatus to be used are in good condition. Seek help from technicians or the lab demonstrator in charge should any problem arises. ƒ
Power supply is working properly ieImax (maximum current) LED indicator is disable. Maximum current will retard the dial movement and eventually damage the equipment. Two factors that will light up the LED indicator are short circuit and insufficient supply of current by the equipment itself. To monitor and maintain a constant power supply, the equipment must be connected to circuit during voltage measurement. DMM are not to be used simultaneously with oscilloscope to avert wrong results. ƒ
Digital millimetre (DMM) with low battery indicated is not to be used. By proper connection, check fuses functionality (especially important for current measurement). Comprehend the use of DMM for various functions. Verify measurements obtained with theoretical values calculated as it is quite often where 2 decimal point reading and 3 decimal point reading are very much deviated. ƒ
The functionality of voltage waveform generators are to be understood. Make sure that frequency desired is displayed by selecting appropriate multiplier knob. Improper settings (ie selected knob is not set at minimum (in direction of CAL – calibrate) at the bottom of knob) might result in misleading values and hence incorrect results. Avoid connecting oscilloscope together with DMM as this will lead to erroneous result. ƒ
Make sure both analog and digital oscilloscopes are properly calibrated by positioning sweep variables for VOLT / DIV in direction of CAL. Calibration can also be achieved by standalone operation where coaxial cable connects CH1 to bottom left hand terminal of oscilloscope. This procedure also verifies coaxial cable continuity. c) Internal circuitry configuration of breadboard or Vero board should be at students’ fingertips (ie holes are connected horizontally not vertically for the main part with engravings disconnecting in‐line holes). d) Students should be rest assured that measured values (theoretical values) of discrete components retrieved ie resistor, capacitor and inductor are in accordance the required ones. e) Continuity check of connecter or wire using DMM should be performed prior to proceeding an experiment. Minimize wires usage to avert mistakes. CONTENTS EXP 1 : AMPLITUDE MODULATION AND DEMODULATION 1.1 OBJECTIVE: 1.2 HARDWARE REQUIRED: 1.3 THEORY: 1
9 1.3.1 AMPLITUDE MODULATI0ON 1.3.2 AMPLITUDE DEMODULATION 1.4 AM MODULATION CIRCUIT DIAGRAM 1.5 MODEL GRAPH 1.6 AM DEMODULATION CIRCUIT DIAGRAM 1.7 PRE LAB QUESTIONS: 1.8 LAB PROCEDURE: 1.9 LAB RESULT: 1.10 POST LAB QUESTIONS: EXP 2 : FREQUENCY MODULATION 2.1 OBJECTIVE 2.2 HARDWARE REQUIRED 2.3 THEORY 2.3.1 FREQUENCY MODULATION USING IC 566 2.4 DESIGN: 2.5 FM MODULATOR CIRCUIT DIAGRAM 2.6 IC 566 PIN DIAGRAM 2.7 PRELAB QUESTIONS 2.8 LAB PROCEDURE 2.9 LAB RESULT 2.10 POST LAB QUESTIONS EXP 3 :PULSE AMPLITUDE MODULATION AND DEMODULATION 16 3.1 OBJECTIVE: 3.2 HARDWARE REQUIRED: 3.3 THEORY: 3.4 DESIGN: 3.5 PAM MODULATOR AND DEMODULATOR CIRCUIT: 3.6 MODEL GRAPH: 3.7 PRE LAB QUESTIONS: 3.8 LAB PROCEDURE: 3.9 LAB RESULT: 3.10 POST LAB QUESTIONS: EXP4. TIME‐DIVISION MULTIPLEX1NG AND DEMULTIPLEXING 4.1. OBJECTIVE 4.2. HARDWARE REQUIRED 4.3. THEORY 4.4 BLOCK DIAGRAM 4.5 MODEL GRAPH: 4.6 PRELAB QUESTIONS 4.7 LAB PROCEDURE: 4.8. LAB RESULT 4.9. POST LAB QUESTIONS 23 30 EXP 5: PRE –EMPHASIS AND DE‐EMPHASIS IN FM 5.1 OBJECTIVE: 5.2 HARDWARE REQUIRED: 5.3 THEORY: 5.3.1 PRE‐EMPHASIS: 5.3.2 DE‐EMPHASIS: 5.4 DESIGN: 5.5 PRE – EMPHASIS CIRCUIT DIAGRAM: 5.6 DE – EMPHASIS CIRCUIT DIAGRAM: 5.7 MODEL GRAPH: 5.8 PRE LAB QUESTIONS: 5.9 LAB PROCEDURE: 5.10 LAB RESULT: 5.11 POST LAB QUESTIONS: EXP 6: AM MODULATOR WITH AWGN NOISE IN MATLAB 39 EXP 7.PRE –EMPHASIS AND DE‐EMPHASIS IN FM USING PSPICE 47 6.1 OBJECTIVE 6.2 SOFTWARE REQUIRED: 6.3 MATLAB® INTRODUCTION 6.4 ALGORITHM: 6.5 PROGRAM FOR AMPLITUDE MODULATION 6.6 PRE LAB QUESTIONS: 6.7 LAB PROCEDURE: 6.8 MODEL GRAPH 6.9 LAB RESULT: 6.10 POST LAB QUESTIONS: 7.1 OBJECTIVE 7.2 SOFTWARE REQUIRED 7.3 ABOUT PSPICE: 7.4 PRE‐EMPHASIS CIRCUIT DIAGRAM 7.5 DE‐EMPHASIS CIRCUIT DIAGRAM 7.6 PRE‐EMPHASIS PROGRAM: 7.7 DE‐EMPHASIS PROGRAM: 7.8 MODEL GRAPH 7.9 PRELAB QUESTIONS: 7.10 LAB PROCEDURE: 7.11 LAB RESULT: 7.12. POST LAB QUESTIONS EXP 8.FM MODULATION IN MATLAB 59 8.1 OBJECTIVE 8.2 SOFTWARE REQUIRED: 8.3 MATLAB® INTRODUCTION 8.4 THEORY 8.4.1 FREQUENCY DIVISION MULTIPLEXING 8.4.2 DE‐MULTIPLEXING: 8.5 ALGORITHM: 8.6 PRELAB QUESTIONS 8.7 LAB PROCEDURE: 8.8 MODEL GRAPH 8.9 LAB RESULT: 8.10 POSTLAB QUESTIONS: EXP 9.DSB‐SC MODULATION IN MATLAB 66 9.1 OBJECTIVE 9.2 SOFTWARE REQUIRED: 9.3 MATLAB® INTRODUCTION 9.4 THEORY: 9.4.1 GENERATION 9.4.2 DEMODULATION 9.5 ALGORITHM: 9.6. PRE LAB QUESTIONS: 9.7 LAB PROCEDURE: 9.8 MODEL GRAPH 9.9 LAB RESULT: 9.10 POST LAB QUESTIONS: EXP. 10. SSB‐SC MODULATION AND DEMODULATION IN MATLAB 75 10.1 OBJECTIVE 10.2 SOFTWARE REQUIRED: 10.3 MATLAB® INTRODUCTION 10.4 Theory: 10.5 ALGORITHM: 10.6. PRE LAB QUESTIONS: 10.7 LAB PROCEDURE: 10.8 MODEL GRAPH 10.9 LAB RESULT: 10.10 POST LAB QUESTIONS: DEPARTMENT OF ECE Faculty of Engineering and Technology, SRMUniversity SRM Nagar, Kattankulathur – 603203, Kancheepuram District, Tamilnadu EC1020 COMMUNICATION ENGINEERING LAB LABORATORY REPORT COVER PAGE Name of the Student : _____________________________________________ Register No. : ________________ Class : III Year / V Semester / B.Tech / ECE / ___ Section Academic Year : 2015‐16 Expt. No. &Title : _____________________________________________ Date of Experiment : ___________ Due Date : ___________ Submission Date : ___________ Instructor(s) : Particulars Pre‐Lab Experimental Data & Analysis (using hardware setup & simulation) Graphs & Conclusion Post‐Lab Promptness, Neatness and Organization Total Marks Max. Marks 5 Marks Obtained 10 5 5 5 30 Remarks : Name / Sign / Stamp with date 1.AMPLITUDE MODULATION AND DEMODULATION 1.1 OBJECTIVE: To construct an amplitude modulator circuit using transistor with Vc=50mv , Vm=8v to satisfy under modulation condition and generate amplitude modulated signal.Calculate the modulation index and also demodulate using envelope detector and reconstruct the modulating signal. 1.2 HARDWARE REQUIRED: S.No Equipment/Component name Specifications/Value Quantity 1 Cathode Ray Oscilloscope (0 – 20MHz) 1 2 Audio Frequency Oscillator (0‐2) MHz 2 3 Regulated power supply (0 ‐30V), 1A 1 4 Resistors 1.5K Ω 2 10 K Ω 3 20 K Ω 1 100 K Ω 2 0.1 µf 1 0.01 µf 1 0.001 µf 3 22 µf 1 5 capacitors 6 Semiconductor Device(Transistor) BC108 1 7 Semiconductor Device( Diode) OA79 1 1.3 THEORY: Modulation is defined as the process by which some characteristics of a carrier signal is varied in accordance with a modulating signal. The base band signal is referred to as the modulating signal and the output of the modulation process is called as the modulation signal. 1 1.3.1 AMPLITUDE MODULATION Amplitude modulation is defined as the process in which amplitude of the carrier wave is varied in accordance with the instantaneous values of the modulating signal. The envelope of the modulating wave has the same shape as the base band signal provided the following two requirements are satisfied 1. The carrier frequency fc must be much greater then the highest frequency components fm of the message signal m (t) i.e. fc >>fm 2. The modulation index must be less than unity. If the modulation index is greater than unity, the carrier wave becomes over modulated. 1.3.2 AMPLITUDE DEMODULATION The process of detection provides a means of recovering the modulating Signal from modulating signal. Demodulation is the reverse process of modulation. The envelope detector circuit is employed to separate the carrier wave and eliminate the side bands. Since the envelope of an AM wave has the same shape as the message, independent of the carrier frequency and phase, demodulation can be accomplished by extracting envelope. An increased time constant RC results in a marginal output follows the modulation envelope. A further increase in time constant the discharge curve become horizontal if the rate of modulation envelope during negative half cycle of the modulation voltage is faster than the rate of voltage RC combination ,the output fails to follow the modulation resulting distorted output is called as diagonal clipping : this will occur even high modulation index. The depth of modulation at the detector output greater than unity and circuit impedance is less than circuit load (Rl>Zm) results in clipping of negative peaks of modulating signal. It is called “negative clipping “ SPECIFICATIONS R1 = R2 = R5 = 10KΩ; R3 = 1.5KΩ; R4 = 20KΩ; C1 = 0.01µF; C2 = 0.001µF; C3 = 0.1 µf; Vc = 50mV; fc = 500KHZ; Vm = 8V; fm = 1KHZ; VCC = 30V; 2 1.4 AM MODULATION CIRCUIT DIAGRAM Fig. 1.1 AM Modulator Circuit 3 1.5 MODEL GRAPH Fig. 1.2 AM Modulated Waveform SPECIFICATIONS C1=0.001μf, C2=22 μf, C3=0.001μf, R1=100KΩ and R2=100KΩ. 1.6 AM DEMODULATION CIRCUIT DIAGRAM Fig. 1.3 AM Demodulator Circuit 4 1.7 PRE LAB QUESTIONS: 1. Define Modulation. 2. Why Modulation is necessary for communication system. 3. What is Baseband signal? 4. Differentiate analog and Digital Modulation. 5. Define Amplitude Modulation and Demodulation? 6. Mention the degrees of Modulation. 7. What is Pilot Carrier? 8. Write an expression for the total power of the Amplitude Modulated wave. 9. What is the efficiency of AM signal? 10. What are the applications of AM system? 1.8 LAB PROCEDURE: I). AMPLITUDE MODULATION 1. The circuit connection is made as shown in the circuit. 2. The power supply is connected to the collector of the transistor. 3. Set the input signal fm as 1KHz and 8volt sinusoidal signal in AFO 4. Set the carrier signal fc as 500KHz and 50 millivolt sinusoidal signal in AFO 5. The AmplitudeModulated Output is taken from the collector of the Transistor. 6. Calculate Emax and Emin from the Output waveform. 7. Calculate modulation index using the formula. Emax – Emin Modulation index (m)% = ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ X 100 Emax + Emin 8. Plot the input signals and obtained AM output waveforms in the graph sheet 5 OBSERVATION: Modulating signal Signal Time Type Period Sine Signal Frequency Amplitude
wave Carrier signal Time Type Period Sine wave Frequency Amplitude
Modulated Output Signal Type Emin Emax Modulation index AM II).AMPLITUDE DEMODULATION 1. The circuit connections are made as shown in the circuit diagram. 2. The amplitude modulated signal from AM generator is given as input to the demodulator circuit. 3. The demodulated output is observed on the CRO 4. Plot the obtained AM demodulated output waveforms in the graph sheet OBSERVATION: Demodulated output Signal Time Period Frequency Amplitude Type Sine wave 6 1.9 LAB RESULT: Thus the amplitude modulation and demodulation were performed and the modulation index for various modulating voltage were calculated. 7 1.10 POST LAB QUESTIONS: 1. What will happen, if modulation index is greater than 100%? 2. What happens to AM signal if ma<1 & ma=1? 3. A 1500Hz signal which has amplitude of 25 V amplitude modulates a 50 MHz carrier which when unmodulated has amplitude of 75V. What frequencies would shown up in the spectrum of AM wave? 4. A complex modulating waveform consisting of a sine wave of amplitude 4 V and frequency 1 kHz plus a cosine wave of amplitude 6 V and frequency 3 kHz amplitude modulates 500 kHz and 10Vpeak carrier voltage. Plot the spectrum of modulated wave. 5. A commercial AM station is broadcasting with an average transmitted carrier power of 10kW; the modulation index is 0.707 for a sinusoidal message signal. Find the transmission power and efficiency. 8 2. FREQUENCY MODULATION 2.1 OBJECTIVE To design a VCO circuit using IC NE566 to generate triangular and square waveforms for a frequency of 93 KHz. With this generated waveform as carrier signal and baseband signal of 1V with a frequency of 5 KHz as a input signal, obtain the frequency modulated waveform and also calculate its modulation index . 2.2 HARDWARE REQUIRED S.No Equipment/Component name
Specifications/Value Quantity
1 Cathode Ray Oscilloscope (0 – 20MHz) 1 2 Audio Frequency Oscillator
(0‐2) MHz
1 3 Regulated power supply (0 ‐30V), 1A 1 4 Resistors 5.6K Ω
1 2.7K Ω 1 3.9K Ω 1 0.01 µf
1 0.001 µf 2 IC NE566 1 5 6 capacitors VCO IC 2.3 THEORY Frequency modulation is a process of changing the frequency of a carrier wave in accordance with the slowly varying base band signal. The main advantage of this modulation is that it can provide better discrimination against noise. 2.3.1 FREQUENCY MODULATION USING IC 566 The IC 566 is a general purpose voltage controlled oscillator which may be used to generate square and triangular waves, the frequency of which is a very linear function of a control voltage. The frequency is also a function of an external resistor and capacitor. 9 Applications of IC 566 1. FM modulation 2. Signal generation 3. Function generation 4. Frequency shift keying 5. Tone generation The Schmitt trigger circuit present in this IC is used to switch the current source between charge and discharge capacitor and triangular voltage developed across the capacitor and the square wave from the Schmitt trigger are provide as the output of the buffer amplifier. The R2 and R3 combination is a voltage divider, the voltage VC must be in the range ¾ VCC< VC < VCC. The modulating voltage must be less than ¾ VCC. The frequency fc can be calculated using the formula fc = 2.4 DESIGN: Let R1 = 2.7KΩ and C1 = 0.001µF For VCC = 12v Vc(at pin no.5) =
fc =
= = 10.493 volts fc = 93.02 KHz 10 2.5 FM MODULATOR CIRCUIT DIAGRAM Fig. 2.1 FM Modulator Circuits using VCO 2.6 IC 566 PIN DIAGRAM Fig.2.2 IC 566 Pin diagram 11 12 2.7 PRELAB QUESTIONS 1. What are the different methods of generating FM signal? 2. Compare FM with AM technique. 3. Give the Carson’s rule to calculate bandwidth of the system. 4. What is the commercial FM frequency range? 5. What is the difference between FM and FSK technique? 2.8 LAB PROCEDURE (1) Frequency Modulation 1. Give the circuit connections as per the circuit diagram. 2. Without input signal, note down the time period Tc of the output signal (at pin no. 3 or pin no.4) 3. Set the input signal fm as 5 KHz and 1volt sinusoidal signal in AFO 4. Observe the FM output waveforms at pin no. 3 (square wave) and pin no. 4 (triangular wave). 5. Note down the Tmin and Tmax from the output FM waveform. (preferably at pin no.4 to note down readings easily) 6. Calculate fmax=1/Tmin and fmin= 1/Tmax 7. Calculate frequency deviation ∆f= (fmax‐fmin)/2 8. Calculate the modulation index m=∆f/fm 9. Plot the input signal and obtained FM output waveforms in the graph sheet OBSERVATION Without input signal Tc= fc = With input signal Tmin Amplitude fmax Tmax fmin modulation index frequeny deviation ∆f m 13 2.9 LAB RESULT Thus the frequency modulation using IC NE566 was performed and the modulation index was calculated. 14 2.10 POST LAB QUESTIONS 1. How FM wave can be converted to PM wave? 2. Write down the significance of Bessel functions in FM modulation. 3. List the applications of FM technique. 4. What is the difference between ratio detector and foster seeley discriminator circuit? 5 Define frequency deviation. 6. Design a VCO circuit with IC NE 566 to generate an output signal with frequency 125 KHz. Assuming C=0.001µF, Control voltage Vc =10.5V and Vcc=12V 15 3.PULSE AMPLITUDE MODULATION AND DEMODULATION 3.1 OBJECTIVE: To modulate a carrier square wave signal has a duty cycle 50% with sinusoidal signal amplitude of 1.5V and a frequency less than 1KHz using transistor as a switch circuit and reconstruct the message signal by using a low pass filter. 3.2 HARDWARE REQUIRED: S.No Equipment/Component name
Specifications/Value Quantity
1 Cathode Ray Oscilloscope (0 – 20MHz) 1 2 Audio Frequency Oscillator
(0‐2) MHz
2 3 Resistors 10K Ω
1 1K Ω 1 3.3K Ω 1 4 capacitors 0.1 µf
2 5 Semiconductor Device(Transistor) BC107 1 3.3 THEORY: The simple pulse modulation technique called Pulse Amplitude Modulation (PAM) proved to be more power efficient than the PWM and consumes constant power for individual pulses like PPM. In PAM the amplitude of the individual pulses are varied according to the amplitude of the modulating signals. The PAM modulator and demodulator circuits simple compared to other kind of modulation and demodulation techniques. There are two kinds of PAM one in which the pulses have the same polarity and the other in which the pulses can have both positive and negative polarity according to the amplitude of the modulating signal. Pulse amplitude modulation is a scheme, which alters the amplitude of regularly spaced rectangular pulses in accordance with the instantaneous values of a continuous message signal. Then amplitude of the modulated pulses represents the amplitude of the intelligence. 16 A train of very short pulses of constant amplitude and fast repetition rate is chosen the amplitude of these pulse is made to vary in accordance with that of a slower modulating signal the result is that of multiplying the train by the modulating signal the envelope of the pulse height corresponds to the modulating wave. The demodulated PAM waves, the signal is passed through a low pass filter having a cut –off frequencies equal to the highest frequency in the modulating signal. At the output of the filter is available the modulating signal along with the DC component. PAM has the same signal to noise ratio as AM and so it is not employed in practical circuits. To implement PAM is to use transistor in switching mode technique. The flow of current from collector to emitter in a bipolar junction transistor is controlled by the voltage at its base. Pulse amplitude modulation is kind of digital modulation technique in which analog message signal is sampled at constant frequency –carrier frequency .A pulse of specified duration is used to sample the message signal. When the pulse is on, the message is sampled and when it is off no message is sampled. This is a basic step in the digitization of analog message signals. The circuits to be implemented in this experiment do a kind of natural sampling. The message is fed as input to a switch and the switch ON/OFF time is controlled by the pulses at sampling frequency. The flow of current from collector to emitter in a bipolar junction transistor is controlled by the voltage at its base. The demodulation of PAM waveform can be implemented by using a low pass filter which passes message signal frequencies but blocks the carrier signal. 3.4 DESIGN: (I) Design a pulse amplitude modulator using transistor as switch: The flow of current from collector to emitter in a bipolar junction transistor is controlled by the voltage at its base, choose the transistor BC107 and apply the sinusoidal message signal of frequency fm< 1 KHz and amplitude Em= 1.5Vpp at the 17 collector .Apply a carrier at the transistor base through a resistor 10KΩ.The carrier pulse amplitude is set as Ec=3Vpp and frequency fc =10KHz. (II)Design of pulse amplitude demodulator: Demodulation is done using RC filter .Design the Low pass filter as per the given equation, R=3.3KΩ is obtained from PAM modulated frequency (fH ) as taken as cut off frequency for RC filter(LPF) with standard value of capacitance C=0.1µF. fH=1/2πRC R=1/2π fHC 3.5 PAM Modulator and Demodulator circuit: Fig 3.1 PAM Modulator and Demodulator circuit 3.6 MODEL GRAPH: Fig. 3.2 PAM Modulated Waveform 18 Fig. 3.3 Pulse Amplitude Demodulated Waveform 3.7 PRE LAB QUESTIONS: 1. What is PAM? 2. Write the transmission bandwidth of PAM signal? 3. What are the functions of reconstruction filter? 4. What is the purpose of Equalizer in PAM demodulator? 5. Draw Flat‐top and natural sampling of PAM with respect to input signal. 3.8 LAB PROCEDURE: (I) PULSE AMPLITUDE MODULATION: 1. Connect the circuit as shown in circuit diagram. 2. Set the Carrier square wave of 3Vpp at 10 KHz using an AFO. 3. Set the modulating signal of 1.5Vpp, 500 Hz by using another AFO. 4. Observe the PAM modulated output wave from CRO across 1KΩ load resistor 5. Plot the graph of the modulating signal, Carrier signal and PAM modulated waveforms. 19 OBSERVATION: Modulating signal Carrier signal Signal Time Frequency Amplitude Signal Time Frequency Amplitude
Type Period Type Period
Sine wave Square wave
Modulated Output Signal Type Time Period Frequency Amplitude PAM (II) PULSE AMPLITUDE DEMODULATION: 1. Connect modulator circuit output to RC filter circuit (LPF). 2. Measure the amplitude and frequency of the demodulated signal from the CRO and verify with that of the modulating input . 3. Plot the demodulated waveform. OBSERVATION: Demodulated output Signal Type Sine wave Time Period Frequency Amplitude 20 3.9 LAB RESULT: Thus the pulse amplitude modulation and demodulation was performed and its corresponding waveforms are plotted. 21 3.10 POST LAB QUESTIONS: 1
Mention the applications of PAM signal. 2
Compare PAM signal with other Pulse modulation. 3
Which device is used to track PAM frequency variations in the clock recovery circuit? 4
What kind of switches is commonly used in PAM multiplexers? 5
What are the advantage and disadvantages of PAM? 6
Consider an analog signal x(t)= 30cos(2000πt)+5sin(6000πt)+10cos(12000πt). Find the Nyquist rate and Nyquist interval of this signal. 7
For the analog signal x(t)= 3cos (100πt),the signal is sampled at the rate of fs=75Hz, what is the discrete time signal obtained after sampling? 22 4. TIME‐DIVISION MULTIPLEX1NG AND DEMULTIPLEXING 4.1. OBJECTIVE To generate the two different signals with the following specifications: Amplitude Frequency Signal 1: 4V 500Hz Signal 2: 5V 1 KHz Transmit both the signals simultaneously in different time slots in the same channel. Recover the individual signal at the receiver end and observe the amplitude and time period of the individual signal. 4.2. HARDWARE REQUIRED: S.No Equipment/Component name
1 Cathode Ray Oscilloscope 2 TDM Trainer kit Specifications/Value Quantity
(0 – 20MHz) 1
ST2102
1
4.3. THEORY An important feature of pulse‐amplitude modulation is conservation of time. That is, for a given message signal, transmission of the associated PAM wave engages the communication channel for only a fraction of the sampling interval on a periodic basis. Hence, some of the time interval between adjacent pulses of the PAM wave is cleared for use by the other independent message signals on a time‐shared basis. By this, we obtain a time‐division multiplex system (TDM), which enables the joint utilization of a common channel by a plurality of independent message signals without mutual interference. Each input message signal is first restricted in bandwidth by a low‐pass pre‐
alias filter to remove the frequencies that are nonessential to an adequate signal representation. The pre‐alias filter outputs are then applied to a commutator, which is usually, implemented using electronic switching circuitry. The function of the commutator is two‐fold: (1) to take a narrow sample of each of the N input messages 23 at a rate fs that is slightly higher than 2W, where W is the cut‐off frequency of the pre‐alias filter, and (2) to sequentially interleave these N samples inside a sampling interval Ts = 1/fs. Indeed, this latter function is the essence of the time‐division multiplexing operation. Following the commutation process, the multiplexed signal is applied to a pulse‐amplitude modulator, the purpose of which is to transform the multiplexed signal into a form suitable for transmission over the communication channel. At the receiving end of the system, the received signal is applied to a pulse‐ amplitude demodulator, which performs the reverse operation of the pulse amplitude modulator. The short pulses produced at the pulse demodulator output are distributed to the appropriate low‐pass reconstruction filters by means of a decommutator, which operates in synchronism with the commutator in the transmitter. . This synchronization is essential for satisfactory operation of the TDM system, and provisions have to be made for it. 4.4BLOCK DIAGRAM Fig 4.1 TDM Trainer Kit –ST2102 Block Diagram 24 4.5 MODEL GRAPH: TRANSMITTER SECTION Fig.4.2 TDM Multiplexed Signal 25 RECEIVER SECTION Fig. 4.3 TDM Demultiplexed Signal 4.6 PRELAB QUESTIONS 1
In what situation multiplexing is used? 2
Mention the types of multiplexing? 3
Why sync pulse is required in TDM? 4
What are the functions of commutator switch? 5
Give the advantages of multiplexing. 26 4.7 LAB PROCEDURE: 1. Signals from the function generator are given to the channels (CH0 ... CH3) present in the transmitter using patch chords. Note down the amplitude and time period of each signal. 2. Measure the amplitude and time period at the transmitter output point. 3. Using a patch chord, connect transmitter output to receiver input. 4. For synchronization purpose, connect the transmitter clock and receiver clock and also transmitter CH0 and receiver CH0. 5. See the output before the filter and after the filter for all the channels connected. OBSERVATION: Transmitter Section Receiver Section Signal 1 Demultiplexed Signal 1 Amplitude Time Period Amplitude Time Period Signal 2 Demultiplexed Signal 2 Amplitude Time Period Amplitude Time Period Transmitter Output Filtered Demultiplexed Signal 1 Amplitude Time Period Amplitude Time Period Filtered Demultiplexed Signal 1 Amplitude Time Period 27 4.8. LAB RESULT Two signals has been transmitted simultaneously in different time slots over the same channel and it has been recovered in the receiver end.
28 4.9. POST LAB QUESTIONS 1. How is synchronization achieved in TDM? 2. What is the limitation of synchronous TDM? 3. How to overcome the limitation in synchronous TDM? 4. Define bandwidth expansion factor. 5. What is the difference between TDM and FDM? 6. Two signals g1(t) and g2(t) are to be transmitted over a common channel by means of time division multiplexing. The highest frequency of g1(t) is 1 KHz and that g2(t) is 1.5 KHz. What is the minimum value of the permissible sampling rate? Justify your answer. 29 5. PRE –EMPHASIS AND DE‐EMPHASIS CIRCUITS USING FM 5.1 OBJECTIVE: To design a pre emphasis circuit to boost the input signal level for a FM transmitter for a cut off frequency of 1KHz. Attenuate the boosted high frequency signals at the receiver side using a deemphasis circuit with a cutoff frequency of 1.6KHz. Analyze the frequency response characteristics of pre emphasis and de emphasis circuits. 5.2 HARDWARE REQUIRED: S.No Equipment/Component name
Specifications/Value Quantity
1 Cathode Ray Oscilloscope (0 – 20MHz) 1 2 Audio Frequency Oscillator
(0‐2) MHz
1 3 Regulated power supply (0 ‐30V), 1A 1 4 Resistors 1K Ω
1 2K Ω 1 10K Ω 2 68K Ω 1 100K Ω 1 5 capacitors 0.1 µf
2 0.001 µf 3 6 Semiconductor Device(Transistor) Q2N2222 1 7 Decade Inductance Box 0.3H 1 5.3 THEORY: During the transmission over a channel, the received signal contains interference (high frequency noise). For demodulated FM signals, the interference power increases as the frequency goes up. Thus, de‐emphasis is applied to the 30 demodulated signal to decrease the power of the interference in high frequency. However, in order to keep the high frequency component of the demodulated message, pre‐emphasis must be applied to the message before going through the FM modulator. 5.3.1 PRE‐EMPHASIS: Pre‐emphasis refers to boosting the relative amplitudes of the modulating voltage for higher audio frequencies. Pre‐emphasis is done at the transmitting side of the frequency modulator. Signals with higher modulation frequencies have lower SNR. In order to compensate this, the high frequency signals are emphasised or boosted in amplitude at the transmitter section of a communication system prior to the modulation process. That is, the pre‐ emphasis network allows the high frequency modulating signal to modulate the carrier at higher level, this causes more frequency deviation. The circuit consist of a transistor, resistor and an inductor. It is basically a high pass filter or Differentiator. A pre‐emphasis circuit produces a constant increase in the amplitude of the modulating signal with an increase in frequency. The cut off frequency is determined by the RC or L/R time constant of the network. Normally, the cut off frequency occurs at the frequency where capacitive reactance or inductive reactance equals R. The cut off frequency is given by the formula fc = R/(2π L) By the use of an active pre‐emphasis network we can reduce the signal loss and distortion with the increase of SNR. Also the output amplitude of the network increases with frequencies above cut off frequency. 5.3.2 DE‐EMPHASIS: De‐emphasis is the complement of pre‐emphasis, in the antinoise system called emphasis. This circuit is used to attenuate the high frequency signal that is boosted at the transmitter section.The circuit is placed at the receiving side. It acts as a low pass filter. The cut off frequency is given by the formula fc = 1/(2πRC) 31 The circuit consists of a passive network consisting of a resistor and a capacitor. It is basically a low pass filter or integrator. The pre‐ emphasis network in front of the FM modulator and a de‐emphasis network at the output of the FM demodulator improves the Signal to Noise Ratio for higher modulating signal frequencies, thus producing a more uniform SNR at the output of demodulator. 5.4 DESIGN: PRE EMPHASIS The cut off frequency is given by the formula fc = R/(2π L) Let fc =1KHz Assume R=2KΩ Therefore L = R/(2π fc) L = 2000/(2*3.14*1000) L = 0.3H DE EMPHASIS The cut off frequency is given by the formula fc = 1/(2π RC) Let fc =1.6KHz Assume R=10KΩ Therefore C1 = 1/(2π fc R) C1 =1/(2*3.14*1600*10000) C1 =0.01µF 32 5.5 PRE – EMPHASIS CIRCUIT DIAGRAM: Fig. 5.1 Pre Emphasis Circuit 5.6 DE – EMPHASIS CIRCUIT DIAGRAM: Fig. 5.2 De Emphasis Circuit 33 5.7 MODEL GRAPH: Fig 5.3 Pre emphasis and De emphasis Characteristics Curve 5.8 PRE LAB QUESTIONS: 1. What is meant by threshold effect? 2. What is pre‐emphasis? 3. How the threshold effect can be avoided? 4. What is fidelity? 5. What is sensitivity and selectivity? 5.9 LAB PROCEDURE: 1. The circuit connections are made as shown in the circuit diagram for the pre‐
emphasis and de‐emphasis circuits. 34 2. A power supply of 10V is given to the pre‐ emphasis circuit. 3. Set the input voltage at 2V, 1 KHz for pre emphasis and 1V,1KHz for de emphasis using AFO . 4. For this constant value of input voltage the values of the frequency is varied and the output voltage is noted on the CRO. 5. A graph is plotted between gain and frequency in a semilog graph sheet for both pre emphasis and de emphasis outputs. OBSERVATION FOR PRE‐EMPHASIS: Vi= Frequency(Hz) Vo Gain= Vo/Vi Gain in dB=20log(Vo/Vi)
35 36 OBSERVATION FOR DE‐EMPHASIS: Vi= Frequency(Hz) Vo Gain= Vo/ Vi
Gain in dB =20log(Vo/Vi) 37 5.10 LAB RESULT: The characteristics of pre‐ emphasis and de‐ emphasis circuits were studied and a graph was drawn between gain (in db) and frequency. 38 5.11 POST LAB QUESTIONS: 1. What is de‐emphasis? 2. How to reduce the noise during transmission in FM ? 3. What should be the time constant for the de emphasis circuit? 4. Why pre‐emphasis is done after modulation? 5. List some applications of pre‐emphasis circuit. 6. Design a circuit to boost the baseband signal amplitude in the FM transmitter for the cut off frequency fc =2KHz as shown in the figure below. 39 6. AM MODULATION WITH AWGN NOISE IN MATLAB 6.1 OBJECTIVE To write and simulate a MATLAB program for amplitude modulation with vc>vm , fc>fm and add an additive white Gaussian noise with SNR=10dB and analyze by varying the SNR value. 6.2 SOFTWARE REQUIRED: MATLAB, Computer installed with Windows XP or higher Version. 6.3 MATLAB® INTRODUCTION MATLAB® is a programming language and numerical computing environment. The name MATLAB® is an acronym for “Matrix Laboratory”. As it name suggests it allows easy manipulation of matrix and vectors. Plotting functions and data is made easy with MATLAB®. It has a good Graphic User Interface and conversion of matlab files to C/C++ is possible. It has several toolboxes that possess specific functions for specific applications. For example Image Processing, Neural Networks, CDMA toolboxes are name a few. An additional package, Simulink, adds graphical multidomain simulation and Model‐Based Design for dynamic and embedded systems. Simulink contains Blocksets that is analogous to Toolboxes. It was created by Mathworks Incorporation, USA. Writing MATLAB programs for modulation applications require knowledge on very few functions and operators. The operators mostly used are arithmetic operators and matrix operators. To know more type in the command prompt ‘help ops’. MATLAB will give a list in that to know on specific operator say addition type in the command prompt ‘help plus’. MATLAB will give how to use and other relevant information. Commonly used graphical functions are plot, figure, subplot, title, and mathematical functions are sin and cos only. The mathematical functions sin and cos are self‐explanatory. The graphical function figure will create a new window and then subsequent graphical commands can be applied. The plot function usually takes two vectors and plot data points according to given vector data. Subplot function is used when two or more plots are drawn on the same figure. As title function 40 suggests it helps to write title of the graph in the figure. For further details type ‘help plot’ or ‘help subplot’ in the command prompt and learn the syntax. 6.4 ALGORITHM: 1. Create a vector ‘t’ (time) that varies from zero to two or three cycles. 2. Create a message signal with single sine frequency or combination of few sine frequencies. All the frequency used in message signal should be less than the carrier frequency likewise amplitude of message signals should be less than carrier amplitude.[AmSin(2πfmt)] 3. Create a carrier signal. [AcSin(2πfct)] 4. Create the modulated signal using the AM equation Am [(1+maSin(2πfmt)]Sin(2πfct) 5. Introduce AWGN noise and observe the changes in the amplitude modulated signal. 6. Plot the message signal, carrier signal, and amplitude modulated signal with AWGN noise. 6.5 PROGRAM FOR AMPLITUDE MODULATION clc; clear all; t=0:0.001:1; vm=5; vc=10; fm=2; fc=25; m=vm*sin(2*pi*fm*t); c=vc*sin(2*pi*fc*t); 41 amp=vc+vm*sin(2*pi*fm*t); am=amp.*sin(2*pi*fc*t); y=awgn(am,10,'measured'); subplot(4,1,1); plot(t,m); xlabel('time'); ylabel('amplitude'); title('message signal'); subplot(4,1,2); plot(t,C); xlabel('time'); ylabel('amplitude'); title('carrier signal'); subplot(4,1,3); plot(t,AM); xlabel('time'); ylabel('amplitude'); title('amplitude modulated signal'); subplot(4,1,4); plot(t,y); xlabel('time'); ylabel('amplitude'); title('amplitude modulated signal with AWGN'); WITH VARYING SNR clc; clear all; t=0:0.001:1; 42 vm=5; vc=10; fm=2; fc=25; m=vm*sin(2*pi*fm*t); c=vc*sin(2*pi*fc*t); amp=vc+vm*sin(2*pi*fm*t); am=amp.*sin(2*pi*fc*t); y1=awgn(am,10,'measured'); y2=awgn(am,100,'measured'); y3=awgn(am,1000,'measured'); subplot(4,1,1); plot(t,am); xlabel('time'); ylabel('amplitude'); title('amplitude modulated signal'); subplot(4,1,2); plot(t,y1); xlabel('time'); ylabel('amplitude'); title('amplitude modulated signal with AWGN [snr10]'); subplot(4,1,3); plot(t,y2); xlabel('time'); ylabel('amplitude'); title('amplitude modulated signal with AWGN[snr100]'); subplot(4,1,4); 43 plot(t,y3); xlabel('time'); ylabel('amplitude'); title('amplitude modulated signal with AWGN[snr1000]'); 6.6 PRE LAB QUESTIONS: 1. What is Matlab? 2. What is Matlab working environment? 3. Can we run Matlab without graphics? 4. What is Simulink? 5. What is AWGN noise? 6.7 LAB PROCEDURE: 1. Open the MATLAB®software by double clicking its icon. 2. MATLAB®logo will appear and after few moments Command Prompt will appear. 3. Go to the File Menu and select a New M‐file. (File ÆNewÆM‐file) or in the left hand corner a blank white paper icon will be there. Click it once. 4. A blank M‐file will appear with a title ‘untitled’ 5. Now start typing your program. After completing, save the M‐file with appropriate name. To execute the program Press F5 or go to Debug Menu and select Run. 6. After execution output will appear in the Command window .If there is an error then with an alarm, type of error will appear in red color. 7. Rectify the error if any and go to Debug Menu and select Run. 44 6.8 MODEL GRAPH Fig 6.1 High Freq Signal Fig 6.2 Message Signal Fig 6.3 Ampitude Modulated Signal with AWGN Channel 45 6.9 LAB RESULT: Thus the amplitude modulation was simulated with AWGN noise. 46 6.10 POST LAB QUESTIONS: 1. What is the difference between stem and plot functions? 2. What is the use of clean and close statements? 3. Find the answer for the following program code a=[1 2 3] ; b=[4 5 6]; c=[a;b] ; d=[ a b]; 4. Explain Matlab application program interface. 5. Explain briefly Matlab mathematical function library. 47 7. PRE –EMPHASIS AND DE‐EMPHASIS IN FM USING PSPICE 7.1 OBJECTIVE To simulate the Pre emphasis and De emphasis circuit using PSPICE Program and verify the output response characteristics. 7.2 SOFTWARE REQUIRED PSPICE – OrCAD 9.2 lite, Computer installed with Windows XP or higher Version. 7.3 ABOUT PSPICE: SPICE is software that stimulates electronic circuits. SPICE can perform various analyses such as DC analysis, Transient analysis, AC analysis and operating point measurements. SPICE contains model for common circuit elements active as well as passive and it is possible of stimulating most electronic circuits. The abbreviation of SPICE is Stimulation Program with Integrated Circuit Emphasis. A circuit is described to a computer by using a file called circuit file. The circuit file contains the circuit details of component and elements, ht information about the sources and the commands for what to calculate and what to provide as output. The circuit file is the input file to the SPICE program, which after executing the commands, produces the result in another file called output file. The description of analysis of a circuit require specifying the following: Element values Types of analysis Nodes Output variables Circuit elements PSPICE output commands Element modes Format of output files Sources Format of circuit files ELEMENT VALUES: The elements values are written in standard floating point notation with optimal scale and unit suffixs 48 Ex: V=Volt, A=Ampere, Hz= Hertz, OHM= ohm Node voltage: The voltage of a point with respect to ground references point. Vname +node ‐node Value Ex: Vcc 10 30v The passive component is also indicated as Rname +node ‐node Values R1 2 3 10k Format of circuit files: The circuit file that can be read by PSPICE may be divided into 5 parts Title Circuit description Analysis description Output description .END ( end of statement) Notes: 1. The first line is the title line and it may contain any type of text. 2. The last line must be the .END command. 3. The order of the remaining lines is not important and does not affect the results of simulations. 4. If the statement is more than one line, the statements can continue on the next line. A continuation line is identified by a plus sign(+) in the first column of the next line 5. The comment line may be included anywhere, precede by an asterisk (*). Within a statement. A comment is preceded by a semicolon (;). 49 6. The number of blanks between items is not significant. The tabs and commas are equivalent to blanks. The tabs and commas are equivalent. 7. The statement or comments can be in either lower case or upper case. 8. If you are not sure of any command or statement, the best thing is to run the circuit file by using that command or statement and see what happened. PSPICE is user friendly software; it gives an error message in the output file that identifies a problem. PRINT statement .Print dc [output variables] The print statement used to get the DC outputs. The maximum number of output variables is 8. .Print statement can be used to print all the desired output variables. The values of the output variables are printed as a table with each column corresponding to one output variable. PLOT statement: The result from dc analysis van also be obtained in the form of line printer plots. The plots are drawn by suing characters. plot dc<output variables> +[<(lower limit),value><(upper limit), value>] The plot statement can be used to plot all the desired output variables. PROBE Statement: Probe is a graphics post processor/ waveform analyser for PSPICE. probe .probe < one or more output variables> In the first form no output variables is specified, the .probe command writes all the node voltages and all the element currents in to the probe.dat file. In the second form where the output variables are specified, only the specified output variables to the probe.dat file. 50 Run the program by typing filename.cir which should place you in probe with an empty screen and a message saying that “ all voltages and currents are available”. That is, data for all node voltages and element currents in the circuit have been passed from pspice to probe Select Add_Trace. Functional graphs are called “traces” by probe. At this point type the names of variables to be traced. Push ENTER to get the trace. Notice that both axes are cutomatically scaled to suit the curve. The Zoom feature of probe displays is very useful if you are interested in an small region of the highlighted. The Zoom in on the peak of the power curve, select Zoom, and select Specify region which is highlighted. The cursor feature of probe is very useful to find maxima or minima values. Select Cursor to go to the cursor submenu. Once the results of the simulations are processed by the .probe command the result are available for graphical displays. Tran statement: Transient analysis can be performed by the .Tran command .tran[/op] print_step end_time (no_print_time [step_ceiling]) [UIC] /op = to print detailed information about the transient analysis operating point Print_step = it specifies the time increment between the results which are printed in tabular form into the output file. End_time = it specifies the final time of the transient calculation. No_print_time = it specifies a value of time, before which results will not be printed to probe for graphing. Step_ceiling = it is the maximum time interval used by the pspice in its internal calculations which is default by end time/50. UIC = directs pspice to use initial conditions given to inductors and capacitors in their defininf L or C statement. 51 Ac source: The general transient analysis for SIN is Sin(offset amplitude freq delay damping factor phase) Frequency response: .ac sweeptype points fstart fstop Sweeptype = LIN,DEC,OCT Fstart = starting frequency must specified in Hz. They also must be positive. Fstop = ending frequency must specified in Hz. They also must be positive. Points = it specifies the number of calculations for every power of ten in the frequency range. Transfer function: It can be used to compute the small signal dc gain, the input resistance and the output resistance of a circuit. .Tf Vout Vin .Tf Iout Iin The .tf command calculates the parameters of Thevenin’s and Norton equivalent circuit for the circuit file.It automatically prints the output and does not require .print,.plot or .probe statement. Dc sweep: The Dc sweep is also known as dc transfer characteristics. The input variable is varied over a range of values. For each value of the input variable. The dc operating and the small signal dc gain are computed by calling the small signal transfer function. .dc LIN swname sstart send sinc .dc oct swname sstart send np .dc DEC swname sstart send np 52 .dc swname list <value> Swname = sweep variable name may be V orI Sstart = start value Send = end value Sinc = increment value of the sweep variable. It should be positive. Np = number of steps. .Lib statement: A library file may be referenced in the circuit file by using the following statement. .lib fname Fname = name of the library file. A library file may contain comments, .model statements, sub circuit definition, .lib statements and .end statements. No other statements are permitted. If fname is omitted, pspice looks for the default file EVAL.LIB. When a .lib command calls for a file, it does not bring the whole text of the library file into the circuit file. It simply reads those models or sub circuits that are called by the main circuit file. 53 7.4 PRE‐EMPHASIS CIRCUIT DIAGRAM Fig 7.1 Pre‐emphasis Circuit 7.5 DE‐EMPHASIS CIRCUIT DIAGRAM: Fig 7.2 De‐Emphasis Circuit 54 7.6 PRE‐EMPHASIS PROGRAM: Vm 6 0 AC 1V sin(0 1V 1KHz) Vcc 1 0 DC 10V R1 1 3 100K R2 3 0 68K L1 1 5 0.3H R3 5 2 2K R4 4 0 1K C1 6 3 0.1uF C2 2 7 0.01uF R5 7 0 10k Q1 2 3 4 Q2N2222 .LIB .AC DEC 10 10Hz 20KHz .PROBE .END 7.7 DE‐EMPHASIS PROGRAM: Vm 1 0 AC 1V sin(0 1V 1KHz) R1 1 2 10k C1 2 0 0.01uF C2 2 0 0.01uF .LIB .AC dec 10 10Hz 20KHz .PROBE .END 55 7.8 MODEL GRAPH Fig 7.3 Preemphasis Output waveform Fig 7.4 Deemphasisoutputwave form 56 7.9PRELAB QUESTIONS: 1. How to include the file in the circuit file? 2. What is the use of Probe comment? 3. What is threshold effect? 4. Which range of frequency is affected by noise interference? 5. How to include a device which is not already existed in pspice library? 7.10 LAB PROCEDURE: 1. Open the Pspice AD Litesoftware by double clicking its icon. 2. After few moments Command window will appear. 3. Go to the File Menu and select a New text file. (File ÆNewÆtext file) 4. A blank text file will appear with a title ‘untitled’ 5. Now start typing your program. After completing, save the text file as .cir with appropriate name. To execute the program go to Debug Menu and select Run. 6. After execution output will appear in the Command window .If there is an error then with an alarm, type of error will appear. 7. Rectify the error if any and go to Debug Menu and select Run. 8. If there is no errors, go to Trace menu and click add trace. Enter the output node voltage and click ok then the output will display. 57 7.11 LAB RESULT: Thus the net list for the given pre‐emphasis and de‐emphasis circuit was written and the output waveforms were plotted. 58 7.12. POST LAB QUESTIONS 1. Which technique is used at the receiver side to reconstruct the original signal? 2. How to add the arrows in the plot? 3. How to reduce the noise during transmission in FM ? 4. Pre emphasis operation is similar to high pass filter explain how? 5. What is the significance of the 3db down frequency? 6. Write a netlist for the given circuit 59 8.FM MODULATION IN MATLAB 8.1 OBJECTIVE To write and simulate a MATLAB program to generate frequency modulated signal with fm=25Hz, fc=400Hz and mf=10. 8.2 SOFTWARE REQUIRED MATLAB ,Computer installed with Windows XP or higher Version.. 8.3 MATLAB® INTRODUCTION MATLAB® is a programming language and numerical computing environment. The name MATLAB® is an acronym for “Matrix Laboratory”. As it name suggests it allows easy manipulation of matrix and vectors. Plotting functions and data is made easy with MATLAB®. It has a good Graphic User Interface and conversion of matlab files to C/C++ is possible. It has several toolboxes that possess specific functions for specific applications. For example Image Processing, Neural Networks, CDMA toolboxes are name a few. An additional package, Simulink, adds graphical multidomain simulation and Model‐Based Design for dynamic and embedded systems. Simulink contains Block sets that are analogous to Toolboxes.It was created by Mathworks Incorporation, USA. MATLAB® has become a defacto programming language for Engineers.Writing MATLAB programs for modulation applications require knowledge on very few functions and operators. The operators mostly used are arithmetic operators and matrix operators. To know more type in the command prompt ‘help ops’. MATLAB will give a list in that to know on specific operator say addition type in the command prompt ‘help plus’. MATLAB will give how to use and other relevant information. Commonly used graphical functions are plot, figure, subplot, title, and mathematical functions are sin and cos only. The mathematical functions sin and cosareself‐explanatory. The graphical function figure will create a new window and then subsequent graphical commands can be applied. The plot function usually takes two vectors and plot data points according to given vector data. In this case it will time Vs signal. Subplot function is used when two or more plots are drawn on the same figure. As title function suggests it helps to write title of the graph in the figure. 60 For further details type ‘help plot’ or ‘help subplot’ in the command prompt and learn the syntax. 8.4 ALGORITHM I.To generate message and carrier signal ,initialize : fc(carrier frequency), fm(modulating signal frequency), t(time axis) 2. Generate message signal as Sin(2πfmt) 3. Generate carrier signal as sin(2πfct). 4. Generate the frequency modulated signal using the FM equation [sin(2πfct+mfSin(2πfmt) ] where mf stands for modulation index. Choose modulation index value more than 1. 5.Plot all the signals 61 8.5 PROGRAM clc; clearall; closeall; fm=25; fc=400; mf=10; t=0:0.0001:0.1; m=sin(2*pi*fm*t); subplot(3,1,1); plot(t,m); xlabel('Time(s)'); ylabel('Amplitude(V)'); title('Message Signal'); grid on; c=sin(2*pi*fc*t); subplot(3,1,2); plot(t,c); xlabel('Time(s)'); ylabel('Amplitude(V)'); title('Carrier Signal'); grid on; y=sin(2*pi*fc*t+(mf.*sin(2*pi*fm*t)));%Frequency changing w.r.t Message signal subplot(3,1,3); plot(t,y); xlabel('Time(s)'); ylabel('Amplitude(V)'); title('Frequency modulated Signal'); grid on; 62 8.6 PRELAB QUESTIONS 1.
An FM signal has an intelligence frequency of 2 kHz and a maximum deviation of 10 kHz. If its carrier frequency is set at 162 MHz, what is its index of modulation? 2.
Define modulation index for FM. 3.
Compare FM and PM. 4.
What is capture effect? 5.
What is the IF Frequency for FM superheterodyne receiver? 8.7 MODEL GRAPH Fig 8.1 Message signal Fig 8.2 Carrier signal Fig 8.3 Frequency modulated signal 63 8.8 LAB PROCEDURE: 1.
Open the MATLAB®software by double clicking its icon. 2.
MATLAB®logo will appear and after few moments Command Prompt will appear. 3.
Go to the File Menu and select a New M‐file. (File ÆNewÆM‐file) or in the left hand corner a blank white paper icon will be there. Click it once. 4.
A blank M‐file will appear with a title ‘untitled’ 5.
Now start typing your program. After completing, save the M‐file with appropriate name. To execute the program Press F5 or go to Debug Menu and select Run. 6.
After execution output will appear in the Command window .If there is an error then with an alarm, type of error will appear in red colour. 7.
Rectify the error if any and go to Debug Menu and select Run. 64 8.9LAB RESULT: Thus the Frequency modulation was performed using MATLAB. 65 8.10.POST LAB QUESTIONS: 1.
Mention advantages of angle modulation over amplitude modulation 2.
What is the bandwidth required for an FM wave in which the modulating frequency signal is 2 KHz and the maximum frequency deviation is 12 KHz? 3.
What is Narrowband FM? 4.
Write the functions of limiter? 5.
Write short notes on direct method of FM generation. 6.
Find the output of the following statement 5^ (2/3) – 25/(2*3) 66 9. DSB‐SC MODULATION IN MATLAB 9.1
OBJECTIVE To write and simulate MATLAB program for DSB‐SC Modulation in time domain and using FFT represent the result in frequency domain . 9.2 SOFTWARE REQUIRED: MATLAB, Computer installed with Windows XP or higher Version. 9.3 MATLAB® INTRODUCTION MATLAB® is a programming language and numerical computing environment. The name MATLAB® is an acronym for “Matrix Laboratory”. As it name suggests it allows easy manipulation of matrix and vectors. Plotting functions and data is made easy with MATLAB®. It has a good Graphic User Interface and conversion of matlab files to C/C++ is possible. It has several toolboxes that possess specific functions for specific applications. For example Image Processing, Neural Networks, CDMA toolboxes are name a few. An additional package, Simulink, adds graphical multidomain simulation and Model‐Based Design for dynamic and embedded systems. Simulink contains Blocksets that is analogous to Toolboxes. It was created by Mathworks Incorporation, USA. Writing MATLAB programs for modulation applications require knowledge on very few functions and operators. The operators mostly used are arithmetic operators and matrix operators. To know more type in the command prompt ‘help ops’. MATLAB will give a list in that to know on specific operator say addition type in the command prompt ‘help plus’. MATLAB will give how to use and other relevant information. Commonly used graphical functions are plot, figure, subplot, title, and mathematical functions are sin and cos only. The mathematical functions sin and cos are self‐explanatory. The graphical function figure will create a new window and then subsequent graphical commands can be applied. The plot function usually takes two vectors and plot data points according to given vector data. Subplot function is used when two or more plots are drawn on the same figure. As title function 67 suggests it helps to write title of the graph in the figure. For further details type ‘help plot’ or ‘help subplot’ in the command prompt and learn the syntax. 9.4 THEORY: DSB‐SC is basically an amplitude modulation wave without the carrier, therefore reducing power waste, giving it a 50% efficiency. This is an increase compared to normal AM transmission, (DSB) has a maximum efficiency of 33.333%, since 2/3 of the power is in the carrier which carries no intelligence, and each sideband carries the same information. Single Side Band (SSB) Suppressed Carrier is 100% efficient. 9.4.1 GENERATION DSB‐SC is generated by a mixer. This consists of a message signal multiplied by a carrier signal. Fig 9.1 Product modulator 68 9.5 ALGORITHM: 1. To generate message and carrier signal, initialize: fc(carrier frequency), fm(modulating signal frequency), fs(sampling frequency), 2. Generate message signal and carrier signal 3. Multiply message and carrier signal to get DSBSC modulated signal in time domain. 4. Take fourier transform of DSBSC modulated signal to get the signal in frequency spectrum. 5. Plot all the signals 69 9.6 PROGRAM: N = 1024; %N point FFT N>fc to avoid freq domain aliasing fs = 4096; % Sample frequency t = (0:N‐1)/fs; fc = 600; %Carrier Frequency fm = 80; %Message Frequency Ec = 20; %Carrier Amplitude Em = 5; %Messagae Amplitude xc=Ec*cos(2*pi*fc*t); xm=Em*cos(2*pi*fm*t); figure(1) subplot(2,1,1),plot(t,xc); title('carrier signal of 600Hz'); xlabel('time (s)'); ylabel('amplitude(V)'); subplot(2,1,2); plot(t,xm); title('message signal of 80Hz'); xlabel('time (s)'); ylabel('amplitude(V)'); % DSB‐SC MODULATION z1= xm.*xc; figure(2) subplot(2,1,1),plot(t,z1); title('DSB‐SC MODULATION IN TIME DOMAIN'); xlabel('time (s)'); ylabel('amplitude (V)'); f = fs * (0 : N/2) / N;%Since the fft result is symmetrical, only the %positive half is sufficient for spectral representation M1 = 2/N*abs(fft(z1,N)); subplot(2,1,2); %Frequency Domain Plot plot(f(1:256),M1(1:256)); title('DSB‐SC MODULATION IN FREQUENCY DOMAIN'); 70 xlabel('Frequency (Hz)'); ylabel('amplitude (V)'); 9.6. PRE LAB QUESTIONS: 1. What is the difference between DSB SC and SSB SC? 2. What are the applications of DSBSC? 3. Write the methods of DSBSC generation. 4. What is the BW for single tone modulating signal with frequency ω? 5. What is the percentage of power saving for DSBSC when compared with AM having 100% depth of modulation? 9.7 LAB PROCEDURE: 1. Open the MATLAB®software by double clicking its icon. 2. MATLAB®logo will appear and after few moments Command Prompt will appear. 3. Go to the File Menu and select a New M‐file. (File ÆNewÆM‐file) or in the left hand corner a blank white paper icon will be there. Click it once. 4. A blank M‐file will appear with a title ‘untitled’. 5. Now start typing your program. After completing, save the M‐file with appropriate name. To execute the program Press F5 or go to Debug Menu and select Run. 6. After execution output will appear in the Command window .If there is an error then with an alarm, type of error will appear in red colour. 7. Rectify the error if any and go to Debug Menu and select Run. 71 9.8 MODEL GRAPH Fig. 9.2 Modulating signal Fig. 9.3 Carrier signal 72 Fig. 9.4 DSB‐SC Modulated signal in time domain Fig. 9.5 DSB‐SC Modulated signal in frequency domain 73 9.9 LAB RESULT: Thus the DSB‐SC modulation was performed using MATLAB. 74 9.10 POST LAB QUESTIONS: 1 Which type of carrier is used in ring modulator? 2. What is the difference between DSB‐FC and DSB‐SC? 3. What are the advantages of DSB SC? 4. What is a Balanced modulator? 5. Write the general equation of DSBSC signal. 6. How will you compute N‐Point DFT using Matlab for N=2096? 75 10.SSB‐SC Modulation and Demodulation in MATLAB 10.1 OBJECTIVE To write and simulate MATLAB program for SSB‐SC Modulation using Hilbert Transform in time domain and using FFT represent the result in frequency domain and hence reconstruct the modulating signal using butterworth filter. 10.2 SOFTWARE REQUIRED MATLAB, Computer installed with Windows XP or higher Version. 10.3 MATLAB® INTRODUCTION MATLAB® is a programming language and numerical computing environment. The name MATLAB® is an acronym for “Matrix Laboratory”. As it name suggests it allows easy manipulation of matrix and vectors. Plotting functions and data is made easy with MATLAB®. It has a good Graphic User Interface and conversion of matlab files to C/C++ is possible. It has several toolboxes that possess specific functions for specific applications. For example Image Processing, Neural Networks, CDMA toolboxes are name a few. An additional package, Simulink, adds graphical multidomain simulation and Model‐Based Design for dynamic and embedded systems. Simulink contains Blocksets that are analogous to Toolboxes. It was created by Mathworks Incorporation, USA. Writing MATLAB programs for modulation applications require knowledge on very few functions and operators. The operators mostly used are arithmetic operators and matrix operators. To know more type in the command prompt ‘help ops’. MATLAB will give a list in that to know on specific operator say addition type in the command prompt ‘help plus’. MATLAB will give how to use and other relevant information. Commonly used graphical functions are plot, figure, subplot, title, and mathematical functions are sin and cos only. The mathematical functions sin and cos are self‐explanatory. The graphical function figure will create a new window and then subsequent graphical commands can be applied. The plot function usually takes two vectors and plot data points according to given vector data. Subplot function is used when two or more plots are drawn on the same figure. As title function 76 suggests it helps to write title of the graph in the figure. For further details type ‘help plot’ or ‘help subplot’ in the command prompt and learn the syntax. 10.4 Theory: An SSB signal is produced by passing the DSB signal through a highly selective band pass filter. This filter selects either the upper or the lower sideband. Hence transmission bandwidth can be cut by half if one sideband is entirely suppressed. This leads to single sideband modulation (SSB). In SSB modulation bandwidth saving is accompanied by a considerable increase in equipment complexity. In DSB‐SC it is observed that there is symmetry in the band structure. So, even if one half is transmitted, the other half can be recovered at the received. By doing so, the bandwidth and power of transmission is reduced by half. Depending on which half of DSB‐SC signal is transmitted, there are two types of SSB modulation 1. Lower Side Band (LSB) Modulation 2. Upper Side Band (USB) Modulation 10.5 ALGORITHM: 1. To generate message and carrier signal, initialize: fc(carrier frequency), (Modulating signal frequency), fs(sampling frequency), N( N point DFT‐no of samples) t(time axis) (Modulating signal amplitude) (Carrier signal amplitude) 2. Generate message signal and carrier signal 3. Apply Hilbert transform to the message signal. 4. Write the expression for LSB or USB as per the requirement LSB =message *carrier (cosine)+Hilbert transform of message*carrier(sine) USB =message *carrier (cosine)‐Hilbert transform of message*carrier(sine) 77 5. Take fourier transform for LSB or USB to get the desired frequency spectrum for modulated signal. 6.. For demodulation, multiply LSB with carrier (cosine) and apply butterworth filter to get demodulated signal or multiply USB with carrier(sine) and apply butterworth filter to get demodulated signal. 7. Plot all the signals 78 10.6 PROGRAM N = 1024; fs = 2048; ts = 1/fs; t=(0:N‐1)/fs; fc = 600; % Limit fc<800 to avoid freqdomain aliasing fm = 100; Vm = 1; Vc = 1; m = Vm*cos(2*pi*fm*t);%Message mh = Vm*cos((2*pi*fm*t)‐pi/2);%Hilbert transform of the messagesignal c=Vc*sin(2*pi*fc*t); sbu = m.*2.*cos(2*pi*fc*t)‐mh.*2.*sin(2*pi*fc*t);%Expression for USB sbl = m.*2.*cos(2*pi*fc*t)+mh.*2.*sin(2*pi*fc*t);%Expression for LSB SBU = 2/N*abs(fft(sbu)); %Fourier Transform of USB SBL = 2/N*abs(fft(sbl)); %Fourier Transform of LSB freq = fs * (0 : N/2) / N; close all; figure(3) subplot(221); plot(10*t(1:200),sbu(1:200),'r');%Time Domain Plot of USB title('Time Domain Representation === USB'); xlabel('Time(s)'); ylabel('Amplitude(V)'); subplot(222) plot(10*t(1:200),sbl(1:200),'b');%Time Domain Plot of LSB title('Time Domain Representation === LSB'); xlabel('Time(s)'); ylabel('Amplitude(V)'); subplot(223); plot(freq,SBU(1:N/2+1)) title('Frequency Domain Representation'); xlabel('Frequency(Hz)'); ylabel('Amplitude(V)'); legend('USB'); 79 subplot(224) plot(freq,SBL(1:N/2+1)); %Frequency domain plot title('Frequency Domain Representation'); xlabel('Frequency(Hz)'); ylabel('Amplitude(V)'); legend('LSB'); figure(4) plot(freq,SBU(1:N/2+1),freq,SBL(1:N/2+1)); title('Frequency Domain Representation'); xlabel('Frequency(Hz)'); ylabel('Amplitude(V)'); legend('USB','LSB'); %Demodulation: md=sbu.*cos(2*pi*fc*t); [b,a]=butter(2,0.1); mf=filter(b,a,md); figure(5) plot(t,mf) title('Demodulated Signal'); xlabel('Time(s)'); ylabel('Amplitude(V)'); figure(1); plot(t,m); xlabel('Time(s)'); ylabel('Amplitude(V)'); title('message signal'); figure(2); plot(t,c); title('Carrier signal'); xlabel('Time(s)'); ylabel('Amplitude(V)'); 80 10.7. PRE LAB QUESTIONS: 1. Define SSB‐SC. 2. What are the advantages of signal sideband transmission? 3. What are the disadvantages of single side band transmission? 4. What are the methods for generating SSB‐SC signal? 5. Compare AM with SSBSC 10.8 LAB PROCEDURE: 1 Open the MATLAB®software by double clicking its icon. 2. MATLAB®logo will appear and after few moments Command Prompt will appear. 3. Go to the File Menu and select a New M‐file. (File ÆNewÆM‐file) or in the left hand corner a blank white paper icon will be there. Click it once. 4. A blank M‐file will appear with a title ‘untitled’ 5. Now start typing your program. After completing, save the M‐file with appropriate name. To execute the program Press F5 or go to Debug Menu and select Run. 6. After execution output will appear in the Command window .If there is an error then with an alarm, type of error will appear in red color. 7. Rectify the error if any and go to Debug Menu and select Run. 10.9 MODEL GRAPH Fig.10.1 Message Signal 81 Fig.10.2 Carrier Signal Fig. 10.3 Time domain representation of USB Fig. 10.4 Time domain representation of LSB 82 Fig. 10.5 Frequency domain representation of USB Fig. 10.6 Frequency domain representation of LSB Fig. 10.7 Demodulated Signal 83 10.9 LAB RESULT: Thus the SSB‐SC modulation and demodulation were performed using MATLAB. 84 10.10 POST LAB QUESTIONS: 1. When is the figure of merit of SSB‐SC system is unity? 2. Compare the noise performance of AM receiver with that of SSB‐ SC receiver. 3. SSB is suitable for speech signals and not for video signals. Why? 4. Mention some applications of SSB‐SC. 5. What do you mean by Hilbert transform and inverse Hilbert Transform? Write few applications of Hilbert transform? 6. Find Hilbert transform of sine wave having amplitude of 2 V and frequency 50 KHz using Matlab program 85