Relate lowpass filter cutoff frequency with real frequency (Hz) to filter from a sampled signal?
My problem is the following:
I have a signal x that was sampled with Fs = 8000 Hz and sampled 1000 samples.
I want to filter the signal using a truncated version of an ideal
discrete lowpass filter getting the filter coefficients b with the
k = -100:1:100 ;
b = (1/Wc) sinc (Wc * k) ;
I want to filter frequencies higher than 2500 Hz, I must somehow
relate the Wc (filter cutoff frequency) with the 2500 Hz frequency
that I want to filter from my sampled signal at 8000 Hz.
I thought that Wc = 2*pi*(2500 / 8000) but, when I when I plot the fft
the frequency response is not what I would expect, as such nor the
filtered signal is filtered correctly.
I filter using
x1 = filter(b,,x) ;
My question is how do I relate Wc with the 2500 frequency cutiff and
the 8000 sampling frequency ?
Thanks a lot!