I have a 50-60Hz signal being sampled at a frequency of 25 kHz & I'm trying to filter all frequencies beyond 70 Hz with a reasonable steep transition band (approx 4 Hz) & good attenuation (~40+ dB).
For this, I tried a Windowed sinc filter using the following parameters :-
Cutoff frequency, fc = 70 / 25000 = 0.00280
Bandwidth, BW = 4 / 25000 = 0.00016
Filter length, M = 4 / 0.00016 = 25000
The problem here is the filter length. The value of 25000 means a window that's 1 second wide while my target is typically around 500-1000 samples, i.e. 1-2 cycles at 50 Hz.
I can't increase the bandwidth & I'm not sure what other options I have to meet this filtering requirement. So, my questions are,
- Is the windowed sinc not a suitable filter for this application?
- Considering that the sampling frequency is so high, shouldn't it be quite easy to achieve this type of filtering with a small filter kernel?
- Is there any other filter that I can use for this? My requirement is to offer good attenuation to all signals beyond 70 Hz using a small window. The choice of the filter isn't of much concern.