FIR filter design with flat passband but equi-ripple stop-band

I am looking for a lowpass FIR filter with flat passband but equi-ripple stopband. In other words, it likes Chebyshev_filter Type II except that it is FIR instead of IIR. Linear-phase is preferred.

Thanks

• Provide more information. – MimSaad May 8 '17 at 8:20

1 Answer

I suggest you the Parks-McClellan method. In Matlab you can use $\tt{firpm}$.

Matlab's (now obsolete function) $\tt{remez}$ also uses this scheme.

The FIR filter is optimally designed to approximate e.g. a Chebyshev filter such that the maximum error between the filter's response and the desired response is minimized.

For more information see this and the examples therein.

• Parks-McClellan gives minmax approximation. The generated FIR has equi-ripple at both passband and stopband. It is not what I am looking for. – Yan Zhu May 8 '17 at 6:06
• Not really. Examples are this and this (and more you can find by just a quick search). – msm May 8 '17 at 6:46
• BTW, you might also find this useful. It also uses a modified version of Parks-McClellan. – msm May 8 '17 at 6:49