Communication System and AM modulation convert to Coherent demodulation

This is the code for AM Modulation. I can not upload the ''Whale sound'' here. 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. Pls give answer.

%% Communication systems I, Spring 2020

% FFT in Matlab, Part I.

clc;

close all;

clear all

file = 'Whale_sound1.mp3'; % this our voice signal

[signal,Fs] = audioread(file);% Fs is already given. We do not need to touch it.

Ts=1/Fs; % sampling interval in time domain

signal=signal(:,1)';

N0 = length(signal);

sound(signal,Fs)

%Plot Sound File in Time Domain

t=0:Ts:Ts*(N0-1); %length of signal in seconds

T0=N0*Ts; % duration of the signal. we add no zero padding

figure();

subplot(2,2,1)

plot(t,signal)

xlabel('Time (s)');

ylabel('Amplitude');

title('Signal in Time Domain');

% Fourier Transform (One-Sided Spectrum)

n = 2^nextpow2(N0); %FFT point is power of 2 to easier implementation

nfft=n;

signalScaled = Ts.*signal; % this is energy signal so we need to multiply with Ts. For power signal the scaling factor will be the number of samples.

S=fft(signalScaled,nfft); % Take FFT (you can take the fft number with a power of 2)

SignalShifFFT = fftshift(S); % two side spectrum both negative and positive frequencies

mx=abs(SignalShifFFT); % Take the absulte spectrum of the signal

freqm = (-nfft/2:nfft/2-1)/(nfft*Ts);

%Plot Sound File in Frequency Domain

subplot(2,2,2)

plot(freqm ,mx); %plot the absolute spectrum

xlabel('Frequency (Hz)')

ylabel('Amplitude')

title('Two-Sided Spectrum of Signal')

%k=0:length(S)-1; % In frequency spectrum, there will be N0 points

%w=k/(length(S)*Ts); % frequency seperation

%% 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')

Answer 1

[Samatha Aleti]

Hi,

There is a similar MATLAB Answer posted here that can help you.