% Analog SignalDt = 0.00005;t = -0.005:Dt:0.005;xa = exp(-1000*abs(t));% Discrete-time SignalTs = 0.001; n = -5:1:5;x = exp(-1000*abs(n*Ts));% Discrete-time Fourier transformK = 500; k = 0:1:K;w = pi*k/K;X = x * exp(-j*n'*w);X = real(X);w = [-fliplr(w), w(2:K+1)];X = [fliplr(X), X(2:K+1)];subplot(1,1,1)subplot(2,1,1);plot(t*1000,xa);xlabel('t in msec.'); ylabel('x2(n)')title('Discrete Signal'); hold onstem(n*Ts*1000,x); gtext('Ts=1 msec'); hold offsubplot(2,1,2);plot(w/pi,X);xlabel('Frequency in pi units'); ylabel('X2(w)')title('Discrete-time Fourier Transform')