Communication System and AM modulation convert to Coherent demodulation

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Furkan Eksi
Furkan Eksi on 3 May 2020
Answered: Sai Sri Pathuri on 6 May 2020
This is the code for AM Modulation. Can you write Matlab code also for AM coherent demodulation. Do not use ammode and amdemod command. You can use diff, filter and integral command in matlab code. Please give answer.
%% AM Modulation
A=0.5; %carrier amplitude;
fc= 10*10^3; %carrier frequency 10 KHz
CarrierSignal= cos(2*pi*fc*t);
ModulatedSignal = [A + signal].*CarrierSignal;
subplot(2,2,3)
plot(t,ModulatedSignal); %plot the absolute spectrum
xlabel('Time')
ylabel('Amplitude')
title('AM Modulated Signal in Time')
% Find the spectrum Modulated Signal by taking FFT
ModulatedSignalFFT=fft(ModulatedSignal,nfft);
ShifFFT = fftshift(ModulatedSignalFFT);
ABSModulatedSignalFFT=abs(ShifFFT)/N0;
freqm = (-nfft/2:nfft/2-1)/(nfft*Ts);
subplot(2,2,4)
%PlotSpectrum of the Modulated Signal
plot(freqm,ABSModulatedSignalFFT); %plot the absolute spectrum
xlabel('Frequency (Hz)')
ylabel('Amplitude')
title('Two-Sided Spectrum of AM Modulated Signal')

Answers (1)

Sai Sri Pathuri
Sai Sri Pathuri on 6 May 2020
You may refer this answer or follow the below steps for basic DSBSC/SSBSC coherent demodulator. Let the received signal be receivedSignal
% output of Product Modulator
v = receivedSignal*CarrierSignal;
% Pass throught a low pass filter to get the demodulated signal
demodSignal = Hpf(v); % Hpf is the low pass filter. You may create it using Filter designer or builder

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