Need help with band pass filter!

I am told to design a bandpass filter but I used the function bandpass in matlab instead. But when I try it on the frequency-domain data, it gives me some negative value, which is supposed to be positive.

Answer 1

[Star Strider]

Although designed in the frequency domain, digital filters created by bandpass and most other functions operate in the time domain.

If you want to see the effects of the filter in the frequency domain, use the fft (link) function on your time domain signals before filtering and after filtering.

[Duc Tran]

Thanks for your answer. I read many posts and it seems you are a super active member of the community.

[Star Strider]

As always, my pleasure.

I do my best!