%-- %-- specgram demo idea %-- format compact Fs = 8000 Fo = 660 T_total = 1.2; tt = 0:(1/Fs):T_total; %--- W = 1600; %-- Total Frequency Deviation Fch = 990; chch = dchirp(T_total,W, Fs/W).'; y1 = real( chch.*exp(2i*pi*Fch*tt(1:length(chch))) ); %-- figure(1), jkl = 801:1200; subplot(1,1,1), strips(y1(1:2:length(chch)/4),0.06,Fs/2), xlabel('TIME (sec)') title([num2str(W),' BW CHIRP CENTERED at ',num2str(Fch),' Hz']) figure(2), sound(y1,Fs) Fmax = Fs/2; Nfft = 128; Nover = 32; nn = 1:2:fix(length(chch)); [B,F,T] = specgram(y1(nn),Nfft,Fmax,[],Nover); subplot(1,1,1), imagesc(T,F,db(B,40)); title([num2str(W),' BW CHIRP CENTERED at ',num2str(Fch),' Hz']) axis xy, colormap(1-gray) ylabel('FREQUENCY (Hz)'), xlabel('TIME (sec)') drawnow, sound(y1,Fs) B1 = B; F1 = F; T1 = T; keyboard %--- Fc = 1.3; y2 = vco( sawtooth(2*pi*Fc*tt,0.5), [300 800], Fs ); %-- figure(3), sound(y2,Fs) Fmax = Fs/4; Nfft = 128; Nover = 100; nn = 1:4:fix(length(y2)); [B,F,T] = specgram(y2(nn),Nfft,Fmax,[],Nover); subplot(1,1,1), imagesc(T,F,db(B,40)); title(['UP-DOWN MODULATED CHIRP']) axis xy, colormap(1-gray) ylabel('FREQUENCY (Hz)'), xlabel('TIME (sec)') drawnow, sound(y2,Fs) B2 = B; F2 = F; T2 = T; keyboard %--- Fc = 4; y3 = vco( sin(2*pi*Fc*tt), [400 700], Fs ); %-- figure(4), sound(y3,Fs) Fmax = Fs/4; Nfft = 128; Nover = 100; nn = 1:4:fix(length(y3)); [B,F,T] = specgram(y3(nn),Nfft,Fmax,[],Nover); subplot(1,1,1), imagesc(T,F,db(B,40)); title(['SINE WAVE MODULATED CHIRP']) axis xy, colormap(1-gray) ylabel('FREQUENCY (Hz)'), xlabel('TIME (sec)') drawnow, sound(y3,Fs) B3 = B; F3 = F; T3 = T; keyboard %--- load chirp %-- creates y and Fs y4 = y'; clear y; %-- figure(5), sound(y4,Fs) Fmax = Fs; Nfft = 256; Nover = 200; Ly = round(0.75*Fs); nn = 1:1:Ly; [B,F,T] = specgram(y4(nn),Nfft,Fmax,[],Nover); subplot(1,1,1), imagesc(T,F,db(B,40)); title(['BIRD CHIRP']) axis xy, colormap(1-gray) ylabel('FREQUENCY (Hz)'), xlabel('TIME (sec)') drawnow, sound(y4,Fs) B4 = B; F4 = F; T4 = T; keyboard %--- figure(6) subplot(2,2,1), imagesc(T1,F1,db(B1,40)); axis xy, grid title([num2str(W),' BW CHIRP CENTERED at ',num2str(Fch),' Hz']) ylabel('FREQ (Hz)'), xlabel('TIME (sec)') subplot(2,2,2), imagesc(T2,F2,db(B2,40)); axis xy, grid title(['UP-DOWN MODULATED CHIRP']) ylabel('FREQ (Hz)'), xlabel('TIME (sec)') subplot(2,2,3), imagesc(T3,F3,db(B3,40)); axis xy, grid title(['SINE WAVE MODULATED CHIRP']) ylabel('FREQ (Hz)'), xlabel('TIME (sec)') subplot(2,2,4), imagesc(T4,F4,db(B4,40)); axis xy, grid title(['BIRD CHIRP']) ylabel('FREQ (Hz)'), xlabel('TIME (sec)') colormap(1-gray) drawnow
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McClellan, Schafer, and Yoder, Signal Processing First, ISBN 0-13-065562-7.
Prentice Hall, Upper Saddle River, NJ 07458.
© 2010 Pearson Education, Inc.