COMMUNICATIONS QUESTION. PLEASE SHOW ALL WORK SO I CAN UNDERSTAND THE PROCESS So

Question

COMMUNICATIONS QUESTION. PLEASE SHOW ALL WORK SO I CAN UNDERSTAND THE PROCESS

Source code is as follows

Fs=8000;

N=Fs*10;

FFTsize=1024;

y=wavrecord(N,Fs);

Y=spectrum(y,FFTsize);

Freq=[0:Fs/FFTsize:Fs/2];

Time=[1:N]/Fs;

subplot(2,1,1),plot(Time,y),ylabel('Amplitude'),xlabel('Time(s)');

subplot(2,1,2),plot(Freq,10*log10(Y/max(Y))),ylabel('Spectrum(dB)'),xlabel('Frequency(Hz)');

Computer Problem. Capture two voice/music signals with your computer sound card, let them be two message signals m1(t) and m2(t). Generate QAM signal sit). Implement coherent QAM demodulation. Examine both the coherent case and the noncoherent case (i.e., carrier frequency synchronized or non-synchronized, and carrier phase synchronized and lion-synchronized). Note that you need to compare both the frequency lion-coherent and the phase non-coherent cases. Draw the plot of the signals, and find the demodulation results by listening to the demodulated signal. Hand in your source code, some typical plots of signals, and your observations and conclusions. You can use the source code in Problem 2.26, Page 73, to get the samples. You can use wavplay() command in MATLAB to playback your signal.

Explanation / Answer

Observations and conclusions.
in QAM two signals can be modulated at he same carrier frequency but having a phase difference of 90 degrees. This ia what we call orthogonal signals in time domain. these two signals are sin and cos at the same frequency. after we adding the quadrature modulated signals we transmit it and and in the recieving side coherently demodulate them using the same orthogonal signals which exact frequency and phase synchronization. we go for a low pass digital filter, i have used 10th order FIR filter with proper cutt of frequency so that the signals are captured properly.

If carrier and phase synchronization does not happen the the orthogonality between the quadrature signals is lost and there is cross talk observed between the two communication channels.

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