Matlab hw

% ExPCM.m % Example of sampling, quantization, and zero order hold clear; clf; td=0.002; % original sampling rate 500 Hz t=[0:td:1.]; % time interval of 1 second xsig=sin(2*pi*t)-sin(6*pi*t); % 1Hz+3Hz sinusoids Lsig=length(xsig); Lfft=2^ceil(log2(Lsig)+1); Xsig=fftshift(fft(xsig,Lfft)); Fmax=1/(2*td); Faxis=linspace(-Fmax,Fmax,Lfft); ts=0.02; % new sampling rate=50Hz Nfact=ts/td; % send the signal through a 16-Level uniform quantizer [s_out,sq_out,sqh_out1,Delta,SQNR]=sampandquant(xsig,16,td,ts); % obtained the PCM signal which is % -sampled , quantized , and zero-order hold signal sqh_out % plot the original signal and the PCM signal in time domain figure(1); subplot(211); sfig1=plot(t,xsig,'k',t,sqh_out1(1:Lsig),'b'); set(sfig1,'Linewidth',2); title('Signal g(t) and its 16 level PCM signal'); xlabel('time (sec)'); % send the signal through a 16-Level uniform quantizer [s_out,sq_out,sqh_out2,Delta,SQNR]=sampandquant(xsig,4,td,ts); % obtained the PCM signal which is % -sampled , quantized , and zero-order hold signal sqh_out % plot the original signal and the PCM signal in time domain subplot(212); sfig2=plot(t,xsig,'k',t,sqh_out2(1:Lsig),'b'); title('Signal g(t) and its 4 level PCM signal'); xlabel('time (sec)'); Lfft=2^ceil(log2(Lsig)+1); Fmax=1/(2*td); Faxis=linspace(-Fmax,Fmax,Lfft); SQH1=fftshift(fft(sqh_out1,Lfft)); SQH2=fftshift(fft(sqh_out2,Lfft)); % Now use LPF to filter the two PCM signals BW=10; % Bandwith is no larger than 10 Hz H_lpf=zeros(1,Lfft); H_lpf(Lfft/2-BW:Lfft/2+BW-1)=1; % ideal LPF S1_recv=SQH1.*H_lpf; s_recv1=real(ifft(fftshift(S1_recv))); % reconstructed f- domain s_recv1=s_recv1(1:Lsig); S2_recv=SQH2.*H_lpf; s_recv2=real(ifft(fftshift(S2_recv))); % reconstructed f- domain s_recv2=s_recv2(1:Lsig); % Plot the filtered signals against original signal figure(2) subplot(211); sfig3=plot(t,xsig,'b-',t,s_recv1,'b-.'); legend('original','recovered') set(sfig3,'Linewidth',2); title('Signal g(t) and filtered 16 level PCM signal'); xlabel('time (sec)'); subplot(212); sfig4=plot(t,xsig,'b-',t,s_recv2(1:Lsig),'b-.'); legend('original','recovered') set(sfig4,'Linewidth',2); title('Signal g(t) and filtered 4 level PCM signal'); xlabel('time (sec)');