I have a signal with many frequencies. how to remove particular frequencies from it

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Ajira
Ajira 2019-9-26
回答： Star Strider 2019-9-27
hey guys,
I need to filter some particular frequencies from my signal, I have a signal which I know that has freq between 50 Hz to over 2450 Hz. now I just want to delete freq bigger than 2450 Hz from my signal. here is my code:
fs = 10000; % Sampling rate [Hz]
Ts = 1/fs; % Sampling period [s]
fNy = fs / 2; % Nyquist frequency [Hz]
duration = 10; % Duration [s]
t = 0 : Ts : duration-Ts; % Time vector
noSamples = length(t); % Number of samples
f = 0 : fs/noSamples : fs - fs/noSamples; % Frequency vector
vp1 = vp(:,:,1)+vp(:,:,2)+vp(:,:,3)+vp(:,:,4)+...
vp(:,:,5)+vp(:,:,6)+vp(:,:,7)+vp(:,:,8)+...
vp(:,:,9)+vp(:,:,10)+vp(:,:,11)+vp(:,:,12)+...
vp(:,:,13)+vp(:,:,14)+vp(:,:,15)+vp(:,:,16)+...
vp(:,:,17)+vp(:,:,18)+vp(:,:,19)+vp(:,:,20)+...
vp(:,:,21)+vp(:,:,22)+vp(:,:,23)+vp(:,:,24);
x_fft = abs(fft(vp1));
hold on
%Plot
figure(1);
subplot(2,1,1);
plot(t,vp1);
subplot(2,1,2);
plot(f,x_fft);
xlim([0 fNy]);
and here is the result :
fig.png

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回答（2 个）

Marco Dellantonio
Marco Dellantonio 2019-9-26
You want to delete frequency above a certain thresold. You can simply check the index which corresponds to the thresold frequency and replace the magnitude of the Fourier Transform with 0 for every element of the modulus (a simple cicle is needed).
Star Strider
Star Strider 2019-9-27
Use the lowpass function (R2018a and later).

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