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Theory: Modulation of SSB SC Signal:: Ece 2 Year University Roll: Lab: EC 491

The document outlines an experiment to study the modulation and demodulation of SSB-SC signals using the phase shift method. It details the objectives, theoretical background, procedures for both modulation and demodulation, and includes a block diagram for clarity. The conclusion confirms the successful completion of the experiment and the learning outcomes related to SSB SC signal processing.

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raisen09032000
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17 views6 pages

Theory: Modulation of SSB SC Signal:: Ece 2 Year University Roll: Lab: EC 491

The document outlines an experiment to study the modulation and demodulation of SSB-SC signals using the phase shift method. It details the objectives, theoretical background, procedures for both modulation and demodulation, and includes a block diagram for clarity. The conclusion confirms the successful completion of the experiment and the learning outcomes related to SSB SC signal processing.

Uploaded by

raisen09032000
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Name :

Ece 2nd year

University Roll :

Lab : EC 491

Title : To study the Modulation and De modulation of SSB-SC signal


using phase shift method .

Objective:
 Understand SSB modulation and the difference between SSB
and
DSB modulation

 Learn how to construct SSB modulators


 Learn how to construct SSB demodulators
 Examine the I Q modulator as SSB modulator.
 Possess the necessary tools to evaluate and compare the SSB − SC
modulation to DSB − SC and DSB_TC performance of systems.

Theory :
Modulation of SSB SC signal :
The message signal x(t) is applied to the product modulator M1 and
through a 90o phase shifter to the product modulator M2 .
Hence, we get the Hilbert transform

at the output of the wideband 90o phase shifter .


The output of carrier oscillator is applied as it is to
modulator M1 whereas it s passed through a 90 o phase shifter and
applied to the modulator M2 .

The outputs of M1 and M2 are applied to an adder .


Therefore,

This expression represents the SSB signal with only LSB i.e. it rejects
the USB .
The block diagram of the phase shift method to generate SSB
with LSB is shown in fig. 2 Demodulation De

Demodulation: In this process, the


message signal can be extracted
from SSBSC wave by multiplying it with a
carrier, having the same frequency and the
phase of the carrier used
in SSBSC modulation. The resulting signal is
then passed through a Low Pass Filter. The
output of this filter is the desired
message signal.
Block Diagram of phase shift or ‘I Q’ method :

15.000,000 MHz

LPF

LPF
515.000,00 MHz Q Q
LOZFMIQ
10-M RF RFZFMIQ
10-D LO
I I

15.000,000 MHz
SSB SC spectrum :

-fm0 fm -fc -fm 0Frequencyfc+fm


Freq
A
B
A- Spectrum of baseband signal. B- Spectrum of USSB signal

Procedure:
SSB Modulation
1. Connect the equipment according to Fig.-8.
2. Set the equipment as follow:
Functoin generator I - frequency 100 kHz,
amplitude -5 dBm. Functoin generator Q -
frequency 100 kHz, amplitude -5 dBm. Signal
generator frequency 10 MHz, amplitude 10 dBm.
3. Set the phase between the two function generators to 90◦
4. Set the spectrum analyzer to frequency 10 MHz , span 1 MHz,
resolu- tion bandwidth 10 kHz .
5. Change the phase between the two Function generators
slightly untill you get a ”clean” SSB signal with maximum USSB
attenuation. Measure the amplitude of the SSB signal, why it is
less then -5 dbm?save data on magnetic media.
6. Change the phase between -90, 0, and 90 degrees to get
DSB, USSB, and LSSB signals.save data on magnetic media.
SSB Demodulation

1. Connect the equipment

I
* R
I
* * R *I
LL

90 phase shift
+/- *RF 90 phase shift L
L
Q
Q *R I
* *R *
.
2.Observe the detected I and Q signals on the ocsilloscope display ,
what is the phase difference between these two signal?

3.Verify that the frequency of the detected I signal is the same as the
baseband I Signal. save the detected I signal on magnetic media.

Conclution : We done this experiment successfully .From this


experiment we learn how to generate modulation and demodulation
of SSB SC signal.

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