ENB6060
TELECOMMUNICATIONS A
LABORATORY SHEET 3
Amplitude Modulation
Name:- (Type Your Name Here)
Student ID :- (Type Your Student ID Here)
Objective
This lab sheet will investigate both double sideband suppressed and full carrier modulation techniques.
As part of this lab the modulation index will be reviewed where the results for different modulation
parameters will be presented.
Apparatus
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
AD633JNZ Multiplier (Part B)
MatLab installed on PC in Lab (Part A)
Method
Part A of this lab has been designed to investigate experimentally both DSBSC and Part B to look at DSB
Full Carrier setups. This particular task will be achieved using the AD633JNZ Multiplier from Analog
Devices. By the end of this lab the students will understand the mechanisms behind DSBSC and DSB full
carrier modulation. The students will also be able to identify and calculate the modulation index of
different AM signals
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Revised 5th March 2012
Part A
DSBSC
The AD633 Analog devices Multiplier chip is set up as shown in Figure 1 (Basic Multiplier Connections).
Follow the instructions below to determine the Baseband and Carrier Frequencies:
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
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Baseband Frequency = The Last Digit of your ID multiplied by 100 (see example below)
Carrier Frequency = Baseband signal Frequency multiplied by 10 (see example below)
Baseband Amplitude = 3 V
Carrier Amplitude = 3 V
Frequency Example :- For a student ID = 20900227 the frequency is 7 x 100 = 700 = 700Hz, in this case
the frequency of the carrier signal is going to be 700 x 10 = 7000 = 7 KHz. If the case arises where the last
digit of your ID is 0 then use the second last digit, i.e. for 20900220 use 2. Use The Arbitrary function
Generator to Create the baseband signal and the FGEN to create the carrier signal.
Deliverable A.1:- Paste in a Screen Shot of the input and output signals obtained. Include a brief Figure
title that indicates the frequencies and their amplitudes. Add any additional comments you feel are
necessary to describe the signal.
Deliverable A.2:- use the Log Button on the Oscilloscope
to obtain the data for the output signal.
Write a Matlab script file to plot this data. Paste the graph you obtain into this document along with the
fully commented Matlab code. (see Figure 2 for an example of imported data from a Log file of the
output signal ).
Use the Digital Spectrum Analyzer to observe the spectrum of the signal.
Deliverable A.3:- Paste in a Screen Shot of the input and output signals obtained using the digital
spectrum analyzer, include a brief Figure title with the information you feel is relevant. Add any
additional comments you feel are necessary to describe the signal.
Deliverable A.4:- Discuss the amplitude of the signals in the spectrum analysis. Are the values obtained
what you expected? You may back up your findings using the mathematical equations discussed during
class.
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Figure 1 Basic Multiplier Connections
Amplitude Modulated Signal
0.1
0.08
0.06
0.04
Amplitude (Volts)
0.02
0
-0.02
-0.04
-0.06
-0.08
-0.1
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
Time (seconds)
Figure 2 Imported data from Log File
Deliverable A.5:- Paste a Screen Shot of the output signal obtained. Include a brief Figure title that
indicates the frequencies and their amplitudes. Add any additional comments you feel are necessary to
describe the signal.
Deliverable A.6:- use the Log Button on the Oscilloscope
to obtain the data for the output signal.
Write a Matlab script file to plot this data. Paste the graph you obtain into this document along with the
fully commented Matlab code. (see Figure 2 for an example of imported data from a Log file of the
output signal ).
Use the Digital Spectrum Analyzer to observe the spectrum of the signal.
Deliverable A.7:- Paste in a Screen Shot of the input and output signals obtained using the digital
spectrum analyzer, include a brief Figure title with the information you feel is relevant. Add any
additional comments you feel are necessary to describe the signal.
Deliverable A.8:- Discuss the amplitude of the signals in the spectrum analysis. Are the values obtained
what you expected? You may back up your findings using the mathematical equations discussed during
class.
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Part B
Set up the AD633JNZ as shown in Figure 3 (Linear Amplitude Modulator). For this analysis use a Carrier
and baseband signals with the same characteristics of frequency and amplitudes as used in the first part
of this lab unless otherwise stated.
Figure 3 Linear Amplitude Modulator
Deliverable B.1:- Paste a Screen Shot of the output signal obtained. Include a brief Figure title that
indicates the frequencies and their amplitudes. Add any additional comments you feel are necessary to
describe the signal. Indicate in thise case the modulation index of the output signal. Does this agree with
the theoretical calculation?
Deliverable B.2:- use the Log Button on the Oscilloscope
to obtain the data for the output signal.
Write a Matlab script file to plot this data. Paste the graph you obtain into this document along with the
fully commented Matlab code. (see Figure 2 for an example of imported data from a Log file of the
output signal ).
Deliverable B.3:- Paste a Screen Shot of the output signal obtained. For the following situations:




Modulation index = 25 %
Modulation index = 50 %
Modulation index = 75 %
Modulation index = 100 %
Include a brief Figure title for each result. Provide the amplitude for both the carrier and baseband
signal in each case. Add any additional comments you feel are necessary to describe the signal. Does this
agree with the theoretical calculation?
Use the Digital Spectrum Analyzer to observe the spectrum of the signal.
Deliverable B.4:- Paste in a Screen Shot of the input and output signals obtained using the digital
spectrum analyzer, include a brief Figure title with the information you feel is relevant. Add any
additional comments you feel are necessary to describe the signal.
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Deliverable B.5:- Discuss the amplitude of the signals in the spectrum analysis. Are the values obtained
what you expected? You may back up your findings using the mathematical equations discussed during
class.
Marking Scheme
Deliverable A.1
Deliverable A.2
Deliverable A.3
Deliverable A.4
Deliverable A.5
Deliverable A.6
Deliverable A.7
Deliverable A.8
Deliverable B.1
Deliverable B.2
Deliverable B.3
Deliverable B.4
Deliverable B.5
Independent Student Work
Marks Assigned
10
10
10
10
10
10
10
10
10
10
10
10
10
10
Note :- The late Penalty is 5 % per day
Deliverable date is 22nd of March 2012 on or before 17:00
The final report is to be uploaded on to Moodle
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Revised 5th March 2012