Numerator of bandpass filter using 'firpm'

I am trying to implement a bandpass filter on ZYNQ 706 each time i pass the numerator it does not filter the exact frequency . I am using 'firpm' command for this. how should i choose the values of firpm so that it filter the exact frequency without any noise. for data reception we are using AD9361.

[yanqi liu]

yes，sir，may be use fft to get fourier display，then get the noise value in fft space