Plotting amplitude spectrum of a signal

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Artyom
Artyom 2023-1-8
评论： Star Strider 2023-1-8
i got this sygnal
tmax=0.5;
t=0:0.001:tmax;
fs=1000;
tsamp=0:1/fs:tmax;
f1 = 18;
f2 = 321.37;
y = sin(2*pi*f1*tsamp) + sin(2*pi*f2*tsamp);
figure();
plot(t, y);
grid on;
how do I plot it's amplitude spectrum?

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采纳的回答

Star Strider
Star Strider 2023-1-8
Ran in:
Try something like this —
tmax=0.5;
t=0:0.001:tmax;
fs=1000;
tsamp=0:1/fs:tmax;
f1 = 18;
f2 = 321.37;
y = sin(2*pi*f1*tsamp) + sin(2*pi*f2*tsamp);
figure();
plot(t, y);
grid on;
L = numel(t);
Fn = fs/2;
NFFT = 2^nextpow2(L);
FTy = fft(y,NFFT)/L;
Fv = linspace(0, 1, NFFT/2+1)*Fn;
Iv = 1:numel(Fv);
figure
plot(Fv, abs(FTy(Iv))*2)
grid on
xlabel('Frequency')
ylabel('Magnitude')
FTyw = fft(y(:).*hann(L),NFFT)/L;
figure
plot(Fv, abs(FTy(Iv))*2)
grid on
xlabel('Frequency')
ylabel('Magnitude')
title('Windowed')
.
  4 个评论
显示 2更早的评论
Artyom
Artyom 2023-1-8
it gives me an error in
FTyw = fft(y(:).*hann(L),NFFT)/L;
says "Undefined function 'hann' for input arguments of type 'double'."
could "hann" be replaced somehow?
Star Strider
Star Strider 2023-1-8
The hann function is part of the Signal Processing Toolbox. Just delete that part of my code, and note that it will still be here if you need it for future reference. (My intent was to demonstrate doing a power-of-2 fft and using a window function.)

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更多回答（1 个）

Sulaymon Eshkabilov
编辑：Sulaymon Eshkabilov 2023-1-8
Ran in:
tmax=0.5;
t=0:0.001:tmax;
fs=1000;
tsamp=0:1/fs:tmax;
f1 = 18;
f2 = 321.37;
y = sin(2*pi*f1*tsamp) + sin(2*pi*f2*tsamp);
figure();
plot(t, y);
grid on;
Y =movmedian(y, 5); % Amplitude
figure
plot(t,Y)
grid on
xlabel('x')
ylabel('|y(x)|')

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