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cheb1ap() - Signal Processing

```[z,p,k] = cheb1ap(n,Rp) returns
the poles and gain of an order n Chebyshev Type
I analog lowpass filter prototype with Rp dB
of ripple in the passband. The function returns the poles in the length n column
vector p and the gain in scalar k. z is an empty
matrix, because there are no zeros. The transfer function isH(s)=z(s)p(s)=k(s−p(1))(s−p(2))…(s−p(n))Chebyshev Type I filters are equiripple in the passband and
monotonic in the stopband. The poles are evenly spaced about an ellipse
in the left half plane. The Chebyshev Type I passband edge angular
frequency ω0 is set
to 1.0 for a normalized result. This is the frequency at which the
passband ends and the filter has magnitude response of 10–Rp/20.```

Syntax

`[z,p,k] = cheb1ap(n,Rp)`

Example

```Frequency Response of an Analog Chebyshev Type I FilterOpen This Example
Design a 6th-order Chebyshev Type I analog lowpass filter with 3 dB of ripple in the passband. Display its magnitude and phase responses.
[z,p,k] = cheb1ap(6,3);       % Lowpass filter prototype
[num,den] = zp2tf(z,p,k);     % Convert to transfer function form
freqs(num,den)                % Frequency response of analog filter```