?? comp_exam3_1.m
字號:
fs = 1000; % sampling frequency
delt = 1/fs; % sampling increment
t = 0:delt:1-delt; % time vector
npts = length(t); % number of points
fn = (0:npts)-(fs/2); % frequency vector for plot
m = 3*cos(2*pi*25*t); % modulation
xc = sin(2*pi*200*t+m); % modulated carrier
asxc = (1/npts)*abs(fft(xc)); % amplitude spectrum
evenf = [asxc((npts/2):npts) asxc(1:npts/2)]; % even amplitude spectrum
stem(fn,evenf,'.k');
xlabel('Frequency - Hz')
ylabel('Amplitude')
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