ELE 3203
Communication systems
Lab 8: SSB Modulation and Demodulation
Student Name ID Number
Faculty Name: Mr. Yacine Adane
Lab Instructor: Ms. Rajalakshmi
Submission Date: November 27, 2020
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Prepared By: Rajalakshmi S Menon, ADW
Objective
To study the function of SSB Modulation and Demodulation using Phase Shift Method.
Apparatus Required
A. Hardware Tools: Computer system
B. Software Tool: MATLAB 7.0 and above version.
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Prepared By: Rajalakshmi S Menon, ADW
Introduction
Single-sideband modulation (SSB) or Single-sideband suppressed-carrier (SSB-SC) is a
refinement of amplitude modulation that more efficiently uses electrical power and
bandwidth. Amplitude modulation produces a modulated output signal that has twice the
bandwidth of the original baseband signal. Single-sideband modulation avoids this bandwidth
doubling, and the power wasted on a carrier, at the cost of somewhat increased device
complexity and more difficult tuning at the receiver.
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Prepared By: Rajalakshmi S Menon, ADW
Theory
The concept of SSB modulation can be represented as shown in Figure 2. The spectrum of an
SSB signal can be theoretically obtained in the manner suggested by first removing the
carrier from the AM signal to produce the DSB spectrum shown in figure 2 (B). Then,
removing one of the two sidebands from the DSB signal, one of the SSB spectra of figure 2
(C) will be obtained. The advantages of SSB modulation are there is no carrier presenting the
spectrum of an SSB signal. Also, only half the frequency bandwidth is required for
communication since only one sideband is transmitted. Therefore, SSB offers efficient power
utilization and economic bandwidth use. These advantages are offset. However, by the fact
that transmission and reception equipment is much more complex.
A B C D
Figure : The concept of SSB modulation
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Prepared By: Rajalakshmi S Menon, ADW
PROCEDURE
The following are required to draw the block diagram as shown in the Figure 2.
1. Carrier Signal Source
2. Message Signal Source
3. Blocks for viewing the signals – Scope
4. Product Block
5. Adder Block
6. Transport Delay
7. Zero Order Hold
We can find these blocks in the following locations of Simulink Library:
Carrier and Message Block
Simulink –> Sources –> Signal Generator
View Block
Simulink –> Sink –> Scope
Product and Adder Block
Simulink –> Math Operations–> Product
Simulink –> Math Operations–> Adder
Transport Delay Block
Simulink –> Continuous–> Transport Delay
Zero Order Hold Block
Simulink –> Discrete–> Zero Order hold
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Prepared By: Rajalakshmi S Menon, ADW
The procedures can be summarized in a three main steps, which are:
1. Arrange the functional blocks “Simulink Model” for modulated and demodulation
frequencies.
2. Assign required parameters to each functional block.
3. Observe the outputs on scope.
SSB Modulation:
Figure : Simulink Block Diagram for SSB Modulation
o Parameters:
- Carrier Signal frequency = 1000Hz, Amplitude=1
- Message Signal frequency = 10Hz, Amplitude =1
- Time Delay of Transport Delay1 = 1/ (4*10)
- Time Delay of Transport Delay2 = 1/ (4*1000)
- Sampling time for Zero Order Hold= 1/25000
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Prepared By: Rajalakshmi S Menon, ADW
SSB Demodulation:
Create a Simulink block diagram for the SSB demodulation with the help of the below Figure 4.
Hint: Use a Continuous VCO Block
Figure : SSB Demodulation Block Diagram
Figure : Simulink Block Diagram for SSB Demodulation
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Prepared By: Rajalakshmi S Menon, ADW
o Parameters:
- Carrier Signal frequency = 1000Hz, Amplitude=1
- Message Signal frequency = 10Hz, Amplitude =1
- Time Delay of Transport Delay_1 = 1/ (4*10)
- Time Delay of Transport Delay_2 = 1/ (4*1000)
- Sampling time for Zero Order Hold= 1/25000
- Analog Filter “Butter”: Lowpass filter, Filter order 4, and passband edge
frequency 30 rad/sec.
- Continuous-Time “VCO”: output amplitude is 1, Quiescent frequency
10Hz, and Input sensitivity 50 Hz/v.
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Prepared By: Rajalakshmi S Menon, ADW
RESULTS AND DISCUSSIONS:
1. Comment on your results for SSB Modulation and attach the scope results
below.
From figure 6, we can observe that the SSB modulation is similar to the carrier signal.
In the waveform and amplitude. The SSB modulation signal is the blue waveform
while the carrier signal is the pink waveform.
Figure : SSB Modulation
2. Attach the Simulink Block diagram of SSB AM Demodulation.
9 Figure : Simulink Block Diagram for SSB Demodulation
Prepared By: Rajalakshmi S Menon, ADW
Figure : SSB Demodulation signal "Brown"
3. Upload your Simulink files.
4. Explain your result. (Identify each block function).
A Message Signal is a signal generator, which is a sine wave that carries information
such as voice, music, and data. Also, its express signal parameters in Hertz.
Also, the Carrier Signal is a signal generator, is a sine wave, but it’s worked to
modulated for transmission by AM. Also, its express signal parameters in Hertz.
Transport Delay1 is input “Message signal” by a specified amount of time. So, initial
output parameters until the simulation times exceeds the time delay parameters.
Transport Delay2 is input “Carrier signal” by a specified amount of time. So, initial
output parameters until the simulation times exceeds the time delay parameters.
Matrix multiply is the modulator (frequency multiplier) that multiplies the modulated
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5. Increase the message signal frequency to 100 Hz. Attach the scope results and
comment on your results.
By increasing the frequency of the message signal. The four signals are different none of
them like another. That mean, all the signals are affected by the message signal. Also, from
below figure 9 we can see that the SSB modulated is become perfect modulation.
Figure : Increasing the Frequency of message signal to 100 Hz
6. Change the Sample time to 1/2500 for the Zero Order Hold. What is the
observation? Attach the scope results and comment on your results.
By changing the zero order hold the SSB modulation affected by increasing or
decreasing it sample time. So, in below figure 10 while increasing the zero-order hold
to 1/250000 the SSB modulation signal it still has the same waveform of carrier
signal. But when it simulates it showed slowly.
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Figure Rajalakshmi
IncreasingS sample
Menon,time
ADWof Zero-Order Hold to be 1/250000
7. What is the function of transport delay in the block diagram? Explain in detail?
The Transport Delay block delays the input by a specified amount of time. This block
is to simulate a time delay. The input to this block is a continuous signal. The
Variable Transport Delay and Variable Time Delay appear as two blocks in the
Simulink block library.
Figure 11: Decreasing sample time of Zero-Order Hold to be 1/12500
8. What is the difference between DSB SC and SSB SC?
Between anything in the world there is a different and this include the DSB-SC and
the SSB-SC. To begin with, the DSB-SC is a double side bend without carrier AM.
Also, it has a smaller number of channels in a given frequency range. It has a
moderate power consumption, moderately redundant, and moderately difficult
reconstruction.
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Prepared By: Rajalakshmi S Menon, ADW
9. What are the parameters used in Simulink for each block in SSB demodulation?
1. Signals:
Parameter Value (Message Signal) Value (Carrier signal)
Wave form Sine Sine
Time (t) Use simulation time Use simulation time
Amplitude 1 1
Frequency 10 1000
Units Hertz Hertz
Interpret vector parameters as 1-D On On
2. Analog Filter “Butter” 4. Continuous- Time “VCO”
Parameter Value (Butter) Parameter Value (VCO)
Design method Butterworth Output amplitude 1
Filter type Lowpass Quiescent frequency (Hz) 10
Filter order 4 Input sensitivity (Hz/ V) 450
Passband edge frequency (rad/s) 30 Initial phase (rad/) 0
10. What are the methods for generating SSB‐SC signal?
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SSB-SC signal are signals where only one of the sidebands is transmitted in an AM
wave. The carrier is also suppressed while transmitting the AM signal. The SSB-SC
signal may be generated by two methods.
I. The frequency discrimination method is based on suppressing on of the
sidebands from the DSB-SC modulated waveform. To get the perfect SSB the
band pass filter, must be sharp cut-off. Which is difficult constraint for
practical implementation.
II. The phase discrimination is based on the time domain representation of the
SSB waveform. Also, this method requires two DSB-SC generators. In
addition, two phase shifters and an adder.
Figure : Phase discrimination method
CONCLUSION AND OBSERVATION
To sum up, this experiment was to study the function of SSB Modulation and Demodulation
using Phase Shift Method. As we know the modulated signal is the encoding of information
in a carrier wave by varying the instantaneous frequency of the wave. Where, demodulation
signal is a received, filtered, and amplified signal to recover the original modulation from the
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carrier. In the SSB the modulation signal is same as the carrier signal. While the
demodulation signal as the message signal. Also, all the signals in the SSB has the same
amplitude.
RUBRICS FOR COMMUNICATION LAB
Each student will be evaluated individually during the lab time according to the following aspects
Students shall be asked any
Individual question during the lab session or
1. 30%
Assessment will be asked to share their screen
while doing
Troubleshooting and
Solving the issues they face during
2. problem solving/ 10%
the simulations
post lab test
3. Introduction/ 5% A detailed introduction and
Objective/ procedure is expected
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Prepared By: Rajalakshmi S Menon, ADW
Procedure
Calculations /Codes/ Calculation/Codes/ Theory to be
4. 5%
Theory. explained
Data collection/
5. Findings / 5% Explanation of the observations
observations
Screenshot of the lab reports
Diagrams / Charts / named well. The waveform need
6. Figures and Plots 10% to clearly visible and the each
with Captions signal has to be distinguished with
captions
Analysis &
Solving the question in Results and
7. Discussion / (theory 15%
Discussions Part
vs actual)
Conclusions/
8. Summary /self- 15% Conclusion of the Lab
reflection
Quality of work
Handwritten report not accepted.
performed including
9. 5% Proper alignment of the writings
quality of lab report,
and screenshot/figures.
neatness etc.
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