1. The document describes creating DSB-SC modulation and demodulation in MATLAB. A 1 kHz message signal is modulated with a 1 MHz carrier signal to perform DSB-SC modulation. 2. To demodulate the signal, it is multiplied with the carrier signal and passed through a low-pass filter to recover the original message signal. Several steps are outlined for both the modulation and demodulation processes. 3. Creating the communication system in MATLAB provided a learning experience and prototype for designing new signals and systems.

1. Creating DSB-SC Generation
and Reconstruction
MD. Toufiq Hasan Anik

2. Topic:
Take a 1 KHz sinusoidal modulating signal and modulate it with a carrier frequency of 1 MHz
to perform DSB-SC modulation. Then detect the original signal from the DSB-SC waveform.
Objective: the main objective of the project is to learning the communication system
calculation or design through mathlab.
Tools:
1. Sin wave: It generates the sine wave or the cos wave by shifting phase
2. Add function: It adds two signals or functions.
3. Product: It multiplies two signals or functions.
4. Scoop: It shows the function or signal by plotting on the graph.
5. Integrator: Integrator integrates the input function or signal but here in the project
we used the integrator as the Low-pass filter.
6. Connector : We used the connector as the wire for connecting between function
Theoretical overview:
DSB-SC Generation:
Here the message signal m(t) =AmCos(wmt)
= Cos (2*pi*1000*t) [f=1 kHz given; Assumed, Am=1]
The carirrer signal c(t)= A Cos (wct)
=Cos (2*pi*1000000*t) [f=1MHz given; Assumed, A=1]
Here
Sam(t)=[Ac+m(t)]cos(wct)

3. The modulated signal
d(t)= Sam(t)* Cos (wct)
= Cos(2*pi*1000*t)* Cos(2*pi*1000000*t)

4. Steps:
1. Took a message signal m(t) =AmCos(wmt). Which amplitude is 1 I assumed and took
the frequency 1 kHz. By shifting the sine wave by pi/2. So, it became ,
Cos (2*pi*1000*t).
2. Secondly, added a constant with it but its amplitude is 0 to make it suppressed carrier.
so the modulation is become 100%.
3. After that, took a carrier signal c(t)= A Cos (wct). ). Which amplitude is 1 I assumed
and took the frequency 1 MHz. By shifting the sine wave by pi/2. So, it became,
Cos (2*pi*1000000*t).
4. To modulate multiplied the carrier signal c(t) with the summed message signal m(t) .
After modulation the carrier signal will create Double Side Band message signal in
frequency domain at -1MHz and 1MHz. And in time domain the carrier signal will be
inside the message signal and will create modulated signal in both side.
In communication system we cut the message signal with band pass filter and transmit it
throw transmitter. But here the message signal is a continuous sinusoidal so I did not cut it
with band pass and transmitted the whole signal.

5. Demodulation:
At receiver we receive the transmitted signal and again demodulate it to get the message
signal.
Here for demodulation part followed some steps.
Steps:
1. Firstly, receive the transmitted signal then for demodulate it again multiplied it with the
carrier signal. As here in project the transmission is occurring directly through wire.
So, we can get the carrier signal direct from the previous generated carrier signal. As
we have the carrier signal and there will be no phase difference complexity.
2. Now, to get the message signal we need to cut it by a low pass filter. As we are passing
the whole continuous sinusoidal message so, we can easily use the integrator as low
pass filter which will generate the message again
3. Finally, we got a message signal .Now we can increase the amplitude with the
amplifier. There is a phase shift of the message signal we can easily detect it and
shifting it we can get desire message signal.

6. Block Diagrams:
1. Mathlab project:
2. Modulating signal:

7. 4. Modulated signal:
5. Demodulated signal:

8. 6. Regenerated or detected signal:
Discussion: DSB-SC is the one of the basic communication system. It was really fun
designing a prototype communication system through mathlab. Hope this experience will help
us to designing new signals and systems.