cheb2ap() - Signal Processing

[z,p,k] = cheb2ap(n,Rs) finds
the zeros, poles, and gain of an order n Chebyshev
Type II analog lowpass filter prototype with stopband ripple Rs dB down from the passband peak value. cheb2ap returns
the zeros and poles in length n column vectors z and p and
the gain in scalar k. If n is
odd, z is length n-1. The transfer
function is
Chebyshev Type II filters are monotonic in the passband and
equiripple in the stopband. The pole locations are the inverse of
the pole locations of cheb1ap,
whose poles are evenly spaced about an ellipse in the left half plane.
The Chebyshev Type II stopband edge angular frequency ω0 is
set to 1 for a normalized result. This is the frequency at which the
stopband begins and the filter has magnitude response of 10–Rs/20.

Syntax

[z,p,k] = cheb2ap(n,Rs)

Example

Frequency Response of an Analog Chebyshev Type II FilterOpen This Example
Design a 6th-order Chebyshev Type II analog lowpass filter with 70 dB of ripple in the stopband. Display its magnitude and phase responses.
[z,p,k] = cheb2ap(6,70);      % Lowpass filter prototype
[num,den] = zp2tf(z,p,k);     % Convert to transfer function form
freqs(num,den)                % Frequency response of analog filter

Output / Return Value

Limitations

Alternatives / See Also

Reference