ETM2046 – Analog & Digital Communications, Trimester 1 2012/13
FACULTY OF ENGINEERING
LAB SHEET
ANALOG AND DIGITAL
COMMUNICATIONS
ETM 2046
TRIMESTER 1 (2012-2013)
ADC 1 – Amplitude Modulation
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ETM2046 – Analog & Digital Communications, Trimester 1 2012/13
ADC 1: AMPLITUDE MODULATION
1. Objectives
Experiment Part 1: AM Modulation
 To recognize a message signal, a carrier signal and an AM modulated waveform.
 To measure the modulation index of an AM signal.
 To study the frequency spectrum of an AM signal.
Experiment Part 2: AM Demodulation
 To demonstrate AM demodulation.
2. Introduction
a) Modulation
To communicate over long distances, we can send a radio frequency (RF) signal between
two antennas, one at the transmitting end and the other at the receiving end. Frequencies
used by AM transmissions are typically between 200 kHz and 25 MHz. A typical radio
frequency of say, 1 MHz, is much higher than the audio frequencies present in the human
voice.
We appear to have two incompatible requirements. A radio system uses frequencies like 1
MHz to transmit over long distances, but we wish to send typical voice frequencies of
between 300 Hz and 3.4 kHz which are quite impossible to transmit by radio signals. This
problem can be overcome by using a process called “modulation”.
A radio system can easily send high frequency signals between a transmitter and a
receiver but this, on its own, conveys no information. Now, if we were to alter the high
frequency signals (in amplitude or frequency or phase or any combination of them) in
correspondence with the variation of the amplitude of the message signal, we could use it
to send information.
Modulation is a process where a “carrier wave” is systematically altered (in amplitude or
frequency or phase or any combination of them) in correspondence with the variation of a
modulating signal, the message signal. The resulting modulated signal will carry the
message information in its amplitude or frequency or phase or any combination of them.
b) Amplitude Modulation (AM)
In Amplitude Modulation, the carrier signal sc (t )  Ac cos c t is modulated in amplitude
by m(t) to produce :
s AM (t )  Ac 1  m(t ) cosc t
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Figure 1: AM
Ac
Carrier (amplitude versus time)
10
8
6
4
2
0
-2
-4
-6
-8
0
20
40
60
80
100
120
Message signal or modulating waveform (amplitude versus time)
20
15
10
Ac
5
0
-5
-10
-15
-20
0
20
40
60
80
100
120
Modulated AM waveform (amplitude versus time)
c) Depth of modulation
Let us consider the following signals:
sc (t )  Ac cos c t
Carrier
:
m(t )  m cos m t
Modulating signal:
Modulated signal :
s AM (t )  Ac 1  m cosmt  cosc t
The amount by which the amplitude of the carrier wave increases or decreases depends
on the amplitude of the information signal and is called the modulation index.
Modulation index, m 
Amax  Ac Amax  Amin Amax  Amin
A B



Ac
2 Ac
Amax  Amin A  B
Percentage of modulation  m  100%
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i) Undermodulation, m < 1
Figure 2: AM with m < 1
A
1.5
1
Ac(min)
B
0.5
Ac(max)
Ac
0
-0.5
-1
-1.5
0
5
10
15
20
25
30
35
40
45
Under this modulation condition, a simple noncoherent demodulation technique such
as envelope detector can be used to recover the original message signal without
distortion.
ii) Overmodulation, m > 1
Figure 3: AM with m > 1
2.5
2
1.5
1
0.5
0
-0.5
-1
-1.5
-2
-2.5
0
5
10
15
20
25
30
35
40
45
Under this modulation condition, noncoherent demodulation will not be able to
recover the original message signal without distortion.
When the message signal is constantly changing, as in a voice or music signal, the
frequency of the modulating envelope and the percentage of modulation are
constantly changing. This constant change makes it practically impossible to
determine the modulation index from the waveform displayed on an oscilloscope.
A solution to the above problem is to set the oscilloscope display to X-Y mode. In
this method, the X input is channel 1 (the message signal) and the Y input is channel
2 (the modulated signal).
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Figure 4: XY mode oscilloscope display
ETM2046 – Analog & Digital Communications, Trimester 1 2012/13
B
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A
The modulation index is given by m 
A B
.
A B
d) Frequency spectrum
Figure 5: Amplitude of spectral components of AM signal (1-sided plot)
m2Ac
m1Ac m3Ac
0
f1
AM
modulation
carrier
Ac
lower
sideband
m2Ac/2
m3Ac/2 m1Ac/2
f2 f3
fc-f2
fc-f3
fc-f1
upper
sideband
m2Ac/2
m1Ac/2 m3Ac/2
fc
fc+f2
fc+f1
fc+f3
The amplitude spectrum of the following signal m(t)

m(t )  Ac m1 cos1t  m2 cos2 t  m3 cos3t
and the corresponding AM signal are shown in
Figure 5.
f

Note that each modulating frequency component produces its own upper and lower side
frequencies around the carrier frequency. All the upper side frequencies are grouped
together and referred to as the upper sideband (USB) and all the lower side frequencies
form the lower sideband (LSB).
If the frequency range of the message signal is from 0 to f3, then, the bandwidth of the
message signal, BW m ( t )  f 3 . The corresponding AM modulated signal will occupy a
frequency range from f c  f 3 to f c  f 3 , and the bandwidth of the corresponding AM
modulated signal is given by
BW AM   f c  f 3    f c  f 3   2 f 3  2 BW m (t ) .
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3. Glossary
 Amplitude modulation (AM) – the process of combining a message signal with a
carrier signal that causes the message signal to vary the amplitude of the carrier signal
 AM signal – an amplitude modulated signal that contains carrier signal and two
sidebands: the lower sideband and the upper sideband
 Audio frequency (AF) – frequencies that a person can hear, typically ranging from 20
Hz to 20 kHz
 Balanced modulator – an amplitude modulator that can be adjusted to control the
amount of modulation
 Bandwidth – the frequency range, in hertz, between an upper and a lower frequency
limits
 Carrier signal – a single, high-frequency signal that can be modulated by a message
signal and transmitted
 Demodulation – the process of recovering or detecting an intelligent/message signal
from a modulated carrier signal
 Double sideband (DSB) – an amplitude modulated signal in which the carrier is
suppressed, leaving only the two sidebands: the lower sideband and the upper
sideband
 Envelopes – the waveform of the amplitude variations of a high frequency signal
 Harmonics – signals with frequencies that are integral multiples of the fundamental
frequency
 Message signal – any signal that contains information
 Mixer – an electronic circuit that combines two frequencies
 Modulation – the process of combining a message signal with a carrier signal that
causes the message signal to vary a characteristic (such as amplitude, frequency,
phase, etc) of the carrier signal
 Radio frequency (RF) – the transmission frequency of electromagnetic signals. RF
frequencies range from about 300 kHz to 1 GHz range
 Sidebands – the frequency bands on each side of the carrier frequency that are formed
during modulation; the sideband frequencies contain the intelligence of the message
signal
4. Material & Equipment Required
i)
ANACOM 1/1, ANACOM 1/2
ii)
Power Supply : +12 V at 1 A, -12 V at 1 A (LJ PS2 IC Power 60 or PS4 System
Power 90)
iii)
Set of 4 mm patching leads
iv)
Dual Trace Oscilloscope
v)
Function Generator
vi)
Spectrum Analyzer
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5. Precautions
i)
All ground terminals at the power supply must be shorted.
ii)
The negative terminal of the oscilloscope probe must be connected to the 0 V
reference on the circuit board during all measurements.
iii)
Remember to switch off the power supply at the end of each subsection, this is to
reduce interference to other experiment.
6. References
i)
LJ Technical System, “An Introduction to Analog Communications – Curriculum
Manual AT02”.
ii)
LJ Technical System, “An Introduction to Analog Communications – Student
Workbook AT02”.
iii)
IFR, “Spectrum Analyzer 2399A Operation Manual”.
iv)
Taub and Schilling, “Principles of Communication Systems”, McGraw-Hill, 1986,
Chapter 3.
7. Experiment Procedures
7.1 Experiment Part 1: AM Modulation
7.1.1 Message Signal, Carrier Signal and AM Signal
i)
Connect the ANACOM 1/1 board to the power supply as shown below:
Figure 6: Power supply connection
+12V –12V +5V
Power Supply PU2
GND
+12V
0V
-12V
ANACOM 1/1
Board
ii)
iii)
ANACOM 1/1 board set-up
 AUDIO INPUT SELECT is switched to INT position.
 MODE is switched to DSB.
 SPEAKER is switched to OFF.
 In the AUDIO OSCILLATOR both the AMPLITUDE preset and the
FREQUENCY preset should be set to maximum (fully clockwise).
 In the BALANCED MODULATOR & BANDPASS FILTER CIRCUIT 1, the
BALANCE preset should be set to maximum (fully clockwise).
 In the OUTPUT AMPLIFIER, decrease the GAIN to its minimum value (fully
counter clockwise).
Switch on the power supply.
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iv)
v)
vi)
vii)
Connect the oscilloscope channel 1 probe to tp1 (test point 1), the message signal
input of the MODULATOR and trigger on channel 1. Set timebase to 50 s/div. This
is an audio signal which is going to be used to amplitude modulate a carrier signal.
Determine the frequency and peak-to-peak voltage of the audio signal from the
oscilloscope display. Record the observed signal.
Set the oscilloscope to DUAL display mode. Connect the oscilloscope channel 2
probe to tp9, the carrier signal input of the MODULATOR and trigger on channel 2.
Set the channel coupling to AC. Set the oscilloscope timebase to 0.2 s/div. This is a
high frequency signal that is going to be used to carry the message signal. Adjust the
vertical scale if necessary.
Determine the frequency and peak-to-peak voltage of the carrier signal from the
oscilloscope display. Record the observed signal.
Connect the channel 2 probe to tp3, the modulated AM signal at the output of the
MODULATOR. Set the oscilloscope vertical mode to DUAL, trigger on channel 1
(the message signal), and timebase to 50 s. Adjust the vertical scale if necessary.
Relate the two waveforms displayed. Record your observation.
Adjust the AMPLITUDE preset and the FREQUENCY preset in the AUDIO
OSCILLATOR.
Investigate the change on the envelope of the AM signal (channel 2) when varying the
amplitude and frequency of the message signal (channel 1).
7.1.2 Modulation Index and Percentage of Modulation
i)
Continue with the previous setting. Ensure that in the AUDIO OSCILLATOR, both
the AMPLITUDE preset and the FREQUENCY preset are set to maximum (fully
clockwise).
ii)
Connect oscilloscope channel 1 probe to tp1, the message signal. Set the oscilloscope
to trigger on channel 1.
iii)
Connect channel 2 probe to tp3, the modulated AM signal.
Measure the vertical height, A and B (in Volts) between the peaks and valleys,
respectively. Calculate the modulation index and the percentage of modulation.
iv)
Set the oscilloscope to XY mode. (For GOS-652 oscilloscope, set VERT mode to XY, set TRIGGER source to X-Y, and set timebase to X-Y.)
Measure A and B, and calculate the modulation index. Compare your results to the
one obtained in the previous step.
7.1.3 Frequency Spectrum
i)
Connect the ANACOM 1/1 board to the power supply.
ii)
ANACOM 1/1 board set-up
 AUDIO INPUT SELECT is switched to EXT position.
 MODE is switched to DSB.
 SPEAKER is switched to OFF.
 In the BALANCED MODULATOR & BANDPASS FILTER CIRCUIT 1, the
BALANCE PRESET should be set to maximum (fully clockwise).
 In the OUTPUT AMPLIFIER, decrease the gain to its minimum value (fully
counter clockwise).
iii)
Switch on the power of the function generator and set it up as follows:
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iv)
v)
vi)
vii)
 Sine wave
 10 kHz
 2 V peak-to-peak
Connect the output of a function generator (positive terminal) to the EXTERNAL
AUDIO INPUT, tp16 of the ANACOM 1/1 board. The ground terminal of the
function generator must be connected to the 0 V reference of the ANACOM 1/1
board.
Switch on the power supply of ANACOM 1/1.
Power on and set the spectrum analyzer as follows (refer to the IFR 2399B Spectrum
Analyzer quick guide in the Appendix if necessary):
 FREQ, Center: 10 kHz
 SPAN, Widthspan: 10 kHz
 AMPL, Atten.: AUTO
 AMPL: Log
 AMPL, Scale..: 10 dB/DIV, Prev..
 AMPL, Unit..: VOLTS, Prev..
 AMPL, Ref. Level: 200 mV
 CPL: All Auto
 CPL, RBW, MNL, CPL, RBW: 300 Hz
For Agilent N9320B Spectrum Analyzer:
 Frequency, Center Freq: 10 kHz
 SPAN, Span: 10 kHz
 Amplitude, Attenuation: Auto
 Amplitude, Scale Type: Log
 Amplitude, Scale/Div: 10
 Amplitude, More, Y Axis: Volts
 Amplitude, Ref. Level: 200 mV
 BW/Avg, Res BW: 300 Hz
 BW/Avg, Video BW: Auto
 BW/Avg, VBW/RBW: Auto
Use the spectrum analyzer probe to monitor the message signal at tp1. Use the MKR
key to activate the marker and use Scroll Key to move the marker around. The
frequency and amplitude level corresponding to the marker location are displayed on
the upper right hand corner of the display screen.
Examine the spectrum (frequency in kHz & amplitude in Volts) of the message signal.
Record the observed amplitude spectrum.
Set the spectrum analyzer as follows (refer to the IFR 2399B Spectrum Analyzer
quick guide in the Appendix if necessary):
 FREQ, Center: 1 MHz
 SPAN, Widthspan: 40 kHz
 Other settings are the same as before.
For Agilent N9320B Spectrum Analyzer:
 Frequency, Center Freq: 1 MHz
 SPAN, Span: 40 kHz
 Other settings are the same as before.
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viii)
ix)
Use the spectrum analyzer probe to monitor the carrier signal at tp9.
Examine the spectrum (frequency in kHz & amplitude in Volts) of the carrier signal.
Record the observed amplitude spectrum.
Set the spectrum analyzer as follows (refer to the IFR 2399B Spectrum Analyzer
quick guide in the Appendix if necessary):
 The settings are the same as before.
Use the spectrum analyzer probe to monitor the AM modulated signal at tp3.
Examine the spectrum (frequency in kHz & amplitude in Volt) of the AM modulated
signal. Record the observed amplitude spectrum.
Set the spectrum analyzer as follows (refer to the IFR 2399B Spectrum Analyzer
quick guide in the Appendix if necessary):
 The settings are the same as before.
Use the spectrum analyzer probe to monitor the transmitted AM modulated signal at
the output of the RF amplifier at tp13.
Record the amplitude spectrum (frequency in kHz & amplitude in V) of the amplified
AM modulated signal.
Compare the spectrum of the amplified AM modulated signal with the spectrum of the
signal before amplification. Investigate the effect of increasing the gain of the
OUTPUT AMPLIFIER on the amplitude spectrum. Record your observations.
Assess Your Comprehension:
1. Describe the characteristics of a message signal, a carrier signal and an AM modulated
signal.
2. Demonstrate your understanding on modulation with reference to AM modulation that
you have experienced in this experiment.
3. Compare the amplitude spectrums obtained from measurements in 7.1.3 with the
theoretical amplitude spectrums. Comment on the differences.
4. State the main function(s) of the RF amplifier stage.
5. Consider a message signal with frequency content ranging from 0 Hz to 10 kHz.
Determine the bandwidth of the message signal and the corresponding AM modulated
signal.
7.2 Experiment Part 2: AM Demodulation
7.2.1 Noncoherent AM Demodulation
i)
In this session, we directly connect the transmitter output to the receiver input instead
of using the pair of antennas. Connect the ANACOM 1/1 and ANACOM 1/2 boards
to the power supply as shown below:
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Figure 7: Power supply connection
+12V –12V +5V
Power Supply
GND
+12V
0V
-12V
+12V
ANACOM 1/2 Board
ANACOM 1/1 Board
ii)
iii)
iv)
v)
vi)
vii)
viii)
0V
ANACOM 1/1 board set-up
 AUDIO INPUT SELECT is switched to INT position.
 MODE is switched to DSB.
 SPEAKER is switched to OFF.
 In the AUDIO OSCILLATOR both the AMPLITUDE preset and the
FREQUENCY preset should be set to maximum (fully clockwise).
 In the BALANCED MODULATOR & BANDPASS FILTER CIRCUIT 1, the
BALANCE preset should be set to maximum (fully clockwise).
 In the OUTPUT AMPLIFIER, increase the GAIN to its maximum value (fully
clockwise).
 The TX OUTPUT SELECT of ANACOM 1/1 should be set to SKT.
 Use jumper wire to connect the TX OUTPUT socket of ANACOM 1/1 to the RX
INPUT socket of the receiver.
ANACOM 1/2 board set-up
 In the AUDIO AMPLIFIER, switch the SPEAKER to ON and decrease the
VOLUME preset to its minimum value (fully counter-clockwise).
 The RX INPUT SELECT of ANACOM 1/2 is switched to SKT.
 In the RF AMPLIFIER, switch the TUNED CIRCUIT SELECT to INT (internal)
position and increase the RF AMPLIFIER GAIN control to maximum (fully
clockwise).
 Set the AGC switch to the IN position.
 Set the DETECTOR switch to the DIODE position.
 Switch the BEAT FREQUENCY OSCILLATOR to the OFF position.
Switch on the power supply.
AUDIO AMPLIFIER VOLUME preset is increased until sound is audible from the
loudspeaker.
Adjust the receiver's Tuning Control until the audio signal from ANACOM 1/1 can
be clearly heard. This should occur between 55 and 65 on the tuning scale. (Fine
tuning for the strongest possible signal may be required.)
On your dual trace oscilloscope, set both the inputs to AC.
On the ANACOM 1/2, the received signal is passed through a series of circuits
including the RF amplifier, mixer, IF amplifiers, diode detector and AF amplifier.
The demodulated signal can be seen at tp39 by using channel 2.
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ix)
Use and trigger on channel 1 to monitor the transmitted AM signal at tp3 of
ANACOM 1/1. Use channel 2 to monitor the transmitted AM signal at tp13 of
ANACOM 1/1. The AM signal should be undermodulation, else ensure that the
BALANCE PRESET in the BALANCED MODULATOR & BANDPASS FILTER
CIRCUIT 1 is tuned to fully clockwise.
Use and trigger on channel 1 to monitor the message signal at tp1 of ANACOM 1/1.
Use channel 2 to monitor the demodulated signal at tp39 of ANACOM 1/2.
Compare the received signal with the transmitted signal.
 Observe if there is any delay between the two signals.
 Examine if there is any distortion on the received signal as compared to the
transmitted signal?
Is there any distortion on the received signal as compared to the transmitted signal? Is
there any delay between the transmitted signal and the received signal?
Repeat the step (x) above by tuning the BALANCE preset in the BALANCED
MODULATOR & BANDPASS FILTER CIRCUIT 1 slowly counter clockwise.
Analyze the changes to the received signal. Record your observation for the cases of
100% modulation and overmodulation.
x)
xi)
Assess Your Comprehension:
1. Determine the maximum value of percentage of modulation of AM signal that enables the
noncoherent receiver above to recover the original message signal without distortion.
8. Marking Scheme
Evaluation for ADC1: Amplitude Modulation experiment is through report writing. The lab
report should be handwritten and follow the standard report format, i.e. begin with
Introduction and end with Conclusion. Students should answer all questions and discuss their
observations. Marks will be given in the scale of 0 to 100, based on the following marking
scheme:






i)



ii)


iii)

iv)
Lab Experiment Overview (10 marks)
 Introduction to the experiment
 Summary of the lab experiment
 Maximum 1 page
Results and Observation (50 marks)
 Explain the results gathered from the experiment
 Answer all questions listed in the experiment
Conclusion and Discussion (10 marks)
 Conclusive remarks on the experiment
Written Communication Skill (30 marks)
Guidelines for Report Writing
A written report should be prepared based on the above experiment using the following
guidelines:
1. Lab Experiment Overview
 Introduction to the experiment
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 Summary of the lab experiment
 Maximum 1 page
2. Results and Observation
 Explain the results gathered from the experiment
 Answer all questions listed in the experiment
3. Conclusion and Discussion
 Conclusive remarks on the experiment
4. Appendices
 Any attachment if available
Note: The report should be submitted within 7 days from the experiment date to the
Telecommunication lab staff (Ms Norizan Mohamed).
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Appendix: A Quick Guide on Using IFR 2399B Spectrum Analyzer
Introduction
A spectrum analyzer is measurement equipment that provides information about frequency
content of an input signal. In brief, it provides amplitude spectrum (amplitude versus
frequency) of an input signal.
Operating Procedure
In order to operate a spectrum analyzer to obtain useful information, we must specify the
required display formats:
i)
The observation frequency range to be displayed (X-axis setting), i.e., the start and
the stop frequency. The frequency difference between the start and the stop
frequencies is called the frequency span.
ii)
Amplitude display units, reference level, scale, and detector mode (log or linear), i.e.,
Y-axis setting.
iii)
Signal coupling options: RBW, sweep time, VBW, input attenuation.
1. Power on procedure
i) Connect the spectrum analyzer to the AC main power supply.
ii) Power on the spectrum analyzer with switch labeled 22 and continue by depressing
toggle switch at 16.
2. Frequency setting
The observation frequency range can be set in either of the following two modes:
i) Center – Span Mode
a) To set the center frequency of measurement range:
 depress FREQ 3,
 select CENTER of the soft function key 2,
 key in the numerical value by using Numeric Key 4, or use Step key 9, or
Scroll key 8.
b) To set the span
 depress SPAN 3,
 select WIDTHSPAN of the soft function key 2,
 key in the numerical value by using Numeric Key 4, or use Step key 9 or
Scroll key 8.
ii) Start – Stop Mode
a) To set the start frequency of measurement range
 depress FREQ 3,
 select START of the soft function key 2,
 key in the numerical value by using Numeric Key 4, or use Step key 9 or
Scroll key 8.
b) To set the stop frequency
 depress FREQ 3,
 select STOP of the soft function key 2,
 key in the numerical value by using Numeric Key 4, or use Step key 9 or
Scroll key 8.
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3. Amplitude/ Power measurement
i) To set the amplitude scale to linear scale or log scale
a) set to log detector
 depress AMPL 3,
 select LOG of the soft function key 2.
b) set to linear detector
 depress AMPL 3,
 select LINEAR of the soft function key 2.
ii) To set the amplitude units to dBm/dBmV/dBuV/volts/watts
 depress AMPL 3,
 select UNITS of the soft function key 2,
 select dBm/dBmV/dBuV/volts/watts of the soft function key 2,
 select PREV.
iii) To set the reference level (top graticule)
 depress AMPL 3,
 select REF LEVEL of the soft function key 2,
 key in the numerical value by using Numeric Key 4, or use Step key 9 or Scroll
key 8.
iv) To set the division of the amplitude scale
a) in log detector mode
 depress AMPL 3,
 select SCALE of the soft function key 2,
 select 10dB/DIV or 5dB/DIV or 2dB/DIV or 1dB/DIV,
 select PREV.
b) in linear detector mode
 no need to set, only full scale is available.
v) To set the input attenuation
 depress AMPL 3,
 select ATTEN [AUTO/MNL] of the soft function key 2,
 key in the numerical value by using Numeric Key 4, or use Step key 9 or Scroll
key 8.
 Note that the ATTEN mode (AUTO or MNL) is changed by pressing the ATTEN
key. In ATTEN MNL (manual) mode, the step size can be set by numeric keys,
step key and scroll key. If ATTEN AUTO mode is selected, the input attenuator
will be coupled by the current reference level automatically.
vi) To set the coupled function to Auto or Manual
a) select AUTO mode
 depress CPL 5,
 select ALL AUTO of the soft function key 2.
b) select MANUAL mode of operation of RBW/sweep time/VBW
 depress CPL 5,
 select RBW[MNL]/SWP TIME[MNL]/VBW[MNL] of the soft function key 2,
 depress CPL 5,
 select RBW/SWEEP TIME/VBW of the soft function key 2.
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Figure 8: Spectrum analyzer
1
2
3
4
5
6
7
8
9
10
16
15
14
13
12
11
17 18 19 20
28 27
26
25
16
24
21
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ETM2046 – Analog & Digital Communications, Trimester 1 2012/13
No
Panel Marking
Explanation of Function
1
(LCD)
2
F1 ~ F7
This is liquid crystal display. It displays the trace waveforms,
the parameter settings, the value of marker, and the soft menu
keys, etc.
These are the soft keys for selecting the soft key menus linked
to the panel key operation.
3
FUNCTION
FREQ
SPAN
AMPL
MEAS
MARKER
MKR
OFF
MKR >
PEAK
CONTROL
TRIG
CPL
DISP
TRACE
4
5
6
SYSTEM
SAVE
FILE
LIMIT
SYSTEM
PRESET
AUX
7
8
9
10
11
12
TG
PRINT
(FDD)
(SCROLL KNOB)
(STEP KEY)
RF INPUT
PROBE
RF OUTPUT
This is the frequency parameter data input section.
This is the span parameter data input section.
This is the amplitude parameter data input section.
This sets the measurement functions.
This key sets marker.
This key’s function is to switch off the marker.
This key is the marker shift function.
This key is related to the peak search function.
This sets the trigger functions.
This sets the RBW, VBW, sweep time.
This key sets the display functions.
This section is for selection of the trace waveform, detection
mode and video average mode.
This key is used for saving the waveforms’ status and limit
lines.
This key is used for recalling the waveforms, status and limit
lines.
This key sets the limit line functions.
This key sets the configuration of the system.
This sets the measurement parameters to default values.
Calibration menus are also included under this key.
This key sets the auxiliary functions, such as FM/AM
demodulation, audio control and squelch control.
This key is used for tracking generator function.
This key is used for printing.
This is the slot to set floppy disk.
This key is used for scrolling the parameters.
These keys are used for shift up/down the parameters.
This is the RF input connector.
This is for RF probe power (2399A only).
This is the tracking generator output connector.
(If option is not attached, this is not provided.)
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ETM2046 – Analog & Digital Communications, Trimester 1 2012/13
13
14
15
DATA ENTRY
, 
0 … 9, +/-,
BS, ENTER
PHONE
KEYBOARD
16
STBY/ON
17
IF OUT
18
19
20
21
22
VIDEO
EXT TRIG
RS-232C
EXT VGA
(OFF/ON)
(inlet)
23
24
25
(Fuse Holder)
PRINTER
SWP GATE
REF I/O 10.0MHz
26
GPIB
27
28
(FAN)
(FG)
These keys set the numeric data, units and special functions.
Increment and decrement input data.
Numeric data setting keys.
This is the output connector for earphone.
This key is used for keyboard, but reserved for other functions
(only for system calibration and maintenance).
This is the power switch. It can be used when the back panel
power switch is on. The power on condition is fetched from the
STBY condition when the key is pressed momentarily. The
equipment is returned to the STBY condition from the power
on condition when the key is pressed again for about 1 second.
This is the IF output connector. This signal is bandwidthcontrolled by the RBW setting.
This is an output connector.
This is an input connector for the external trigger.
This is the RS-232C connector. Connect it to system controller.
This is VGA output for external monitor.
This is the fused AC power switch.
This is the fused AC power inlet to which the supply power
cord is connected.
It contains two lag fuses.
This is for use with printer.
This is an output connector for sweep gate signal.
This is the input/output connector for an external reference
crystal oscillator. When the external reference signal is input to
this connector, the user turns this port on from the front panel.
An indication is supplied at the bottom of the screen.
This is for use with the GPIB interface. It is the connector to an
external system controller. (If option is not attached, this is not
provided.)
This is the cooling fan ventilating internally generated heat.
This is the frame ground terminal.
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ETM2046 – Analog & Digital Communications, Trimester 1 2012/13
FACULTY OF ENGINEERING
LAB REPORT SUBMISSION
ETM2046 ANALOG AND DIGITAL
COMMUNICATIONS
TRIMESTER 1 SESSION 2010/2011
Student Name:
………..………………………………………………………………
Student ID:
………………………………
Lab Group No.:
………………………………
Degree Major:
EE / LE / CE / TE / ME / OPE / MCE / NANO / BMM
Declaration of originality:
I declare that all sentences, results and data mentioned in this report are from my own
work. All work derived from other authors have been listed in the references. I understand
that failure to do this is considered plagiarism and will be penalized.
Note that collaboration and discussions in conducting the experiments are allowed but
copying and any act of cheating in the report, results and data are strictly prohibited
Student signature: …………………………………………
Experiment title:
ADC 1 – Amplitude Modulation
Experiment Date:
………………………………
Table/PC No.:
………………………………
Date Submitted:
……………………................
Lab Instructor Name: ……………………………………… Verified:………………….
(Please get your lab instructor signature after they have verified your result)
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