Chebyshev type II filter

Hi dears,

If the order of the filter is 5 and cutoff frequency is 1.5Hz, then how will I apply the Chebyshev type II filter (low-pass filter) on the signal. The sampling frequency of the signal is 10 Hz?

Thanks

Answer 1

[Star Strider]

See the documentation for: cheb2ord, cheby2, zp2sos and filtfilt.

[MAT-Magic]

Thanks alot for the reply.

Actually, I read this cheby2 command as given below;

[b,a] = cheby2(n,Rs,Ws)

Accroding to the question, I am having this n which is the order of the filter, but I don't know how to find Rs and Ws from the given question. Do you know how to compute these two factors? Thanks

[Star Strider]

As always, my pleasure!

You can get all those from the cheb2ord function output. The arguments are, in order, ‘n’ the filter order, ‘Rs’ the stopband ripple or attenuation, and ‘Ws’ the stopband frequency, here 1.5 Hz, normalized to 1.5/5, where the denominator is the Nyquist frequency. Only ‘Rs’ is a bit mysterious, however it can be whatever you want, within limits, and 50 dB is a typical value, reducing the stopband amplitude to about 0.003 of the passband amplitude. The filter order is calculated from both the passband and stopband frequencies and the desired stopband attenuation, and represents the optimal minimum order that will provide the desired filter performance.

Be sure to use the freqz function after you designed it, to verify that your filter is doing what you want it to.

[MAT-Magic]

Thanks alot Star Strider.

[Star Strider]

As always, my pleasure!