Chebyshev Type-II IIR Filter Design

LIQUID_IIRDES_CHEBY2 is a Chebyshev Type-II filter. This design is similar to that of Chebyshev Type-I, except that the Chebyshev polynomial is inverted. This inverts the magnitude response of the filter and exhibits an equiripple behavior in the stop-band, rather than the pass-band. The analog prototype interface is cheby2_azpkf().

Attention

talk about analog prototype

An example Chebyshev-I design can be seen in the code listing here:

#include <liquid/liquid.h>
int main()
{
    return 0;
}

An example of a digital filter response can be found in the figure below.

Figure 16 Chebyshev-II filter design, \(n=7\), \(f_c=0.2 F_s\), \(A_p=1\) dB, and \(A_s=60\) dB.

Notice how the performance changes as the order increases to 15…