Parks - McClellan filter design

Hi all,

We are asked to design a Parks-McClellan filter with the following specifications,I tried to use firgr and firpm methods however, couldn't be sure how to apply the specifications to the command.

passband filter edge = 2kHz stopband filter edge = 2.5 kHz passband tolerance = stopband tolerance = 0.05 sampling frequency = 8 kHz.

Thanks.

Answer 1

[Wayne King]

If you use fdesign.lowpass with a minimum order design, the default design is the PM equiripple method

To convert the passband tolerance and stopband tolerances to passband ripple in dB and stopband attenuation

 Rp = -20*log10((1-0.05)/(1+0.05));
 Ast = -20*log10((0.05)/(1+0.05));

 Fs = 8000;
 d = fdesign.lowpass('Fp,Fst,Ap,Ast' ,2e3,2.5e3,Rp,Ast,Fs);
 Hd = design(d);

The above will call firpm()