High Pass Digital Filter Design

I have a requirement for 1.1 Hz cutoff. I am trying to replace analog filter with an equivalent digital filter. I don't have the circuit for the filter. I only know the cutoffs. It's a band pass filter with fc1 = 1.1 Hz and fc2 = 3.5 KHz. I am trying to replace the analog filter with a digital/software filter. I am moving the filter after the ADC block and the ADC has a sampling frequncy of 1 MHz.

My approach:

I tried to break the bandpass into High Pass and Low Pass filter. I could achieve the correct response for Low Pass Filter with a cutoff of 3.5 KHz and sampling frequncy of 1 MHz.

I am having hard time achieving correct respose for High Pass Filter with a cutoff of 1.1 Hz.

The dB slope required , outsise cutoff frequencies, is 12 dB/octave (2nd order response). The allowed ripple for pass band is 0.2 dB.

Please give me some insight on how to approach the design

Answer 1

[Benjamin Thompson]

Try using the Filter Designer App in the Signal Processing Toolbox.