I did the following things:
- Generated a 2 Hz sine wave (s1) with sampling frequency 1000 hz
- Generated a 8 Hz sine wave (s2) with sampling frequency 1000 hz
- combined both of them to get a new waveform (s3)
- created a filter with cutoff 4 Hz and gave s3 as input.
filter used is :
[b,a] = fir1(7,4/fs); filter_out = filter(b,a,s3);
where fs is sampling frequency .
I expected that the filter will remove the 8 Hz component from the composite waveform (s3) and the filter output will be a 2 Hz sinewave. ie both filter output and s1 will look alike. But this is what i got.
What is wrong with my understanding/expectation?
Thanks in advance