DSB-SC Modulation and Demodulation Script: Filtering and Analysis of Demodulated Signal - , Assignments of Electrical and Electronics Engineering

Download DSB-SC Modulation and Demodulation Script: Filtering and Analysis of Demodulated Signal - and more Assignments Electrical and Electronics Engineering in PDF only on Docsity! ECGR 4123/5191 Computer Problem #2 3) Partial Solution to Problem 3 Script File Used for the entire Problem % Script File - DSB-SC Modulation and Demodulation % Information signal is a Rectangular Pulse with 1st Null Bandwidth of % 2 rad/s. The carrier frequency, wo = 2*pi*100 rad/s. % Set sampling frequency for time domain. This sampling frequency is used % consistently throughtout the entire example. Sampling frequency needs % to be at leat twice the highest frequency. % % Highest frequency 2*wo + 8*2. The 8*2 rad/s term is required to take % into account the high frequency terms in our information signal. % To obtain "better" plots the sampling frequency is sellected to be 20 % times the carrier frequency. close all clear all wo=2*pi*100; fs = 20*wo; a0 = 2*pi*6; % Select -3dB down point of filter to be at 6 Hz h = exp(-a0.*[0:1/fs:1]); % Note there are better approaches to %designing this filter, but this method is straight forward freqz(h,1,2^15,fs) % Plot of frequency response of the filter t=-10:1/fs:10; % time variable x=((t+1)>0) - ((t-1)>0); % rect information signal y = x.* cos(wo*t); % Modulated signal z = y.* cos(wo*t); % Demodulated signal prior to LPF xhat = filter(h,1,z); %Demodulated signal dtft(x,fs,'Message signal'); dtft(y,fs,'Modeulated signal'); dtft(z,fs,'Demodulated signal prior to LPF'); dtft(xhat,fs,'Received signal'); plot(t,x,'r', 'linewidth', 2) hold on plot(t,xhat/sum(h.^2),'--')