Gauss-Chebyshev

A Gauss-Chebyshev, or transitionally Gaussian filter combines the advantages of both the Gaussian and the Chebyshev response. For low frequencies, the response is approximately Gaussian, which results in a good phase linearity. Above a certain frequency, the transition frequency, the response becomes more like a Chebyshev response, which means good damping.

The command to generate such a filter is

tgauss ( <order> , <ripple> , <damping> ) ;

and results in a transitional Gaussian filter with specified order and ripple in dB, up to a specified damping in dB. For instance tgauss(4, 0.01, 6); results in a filter which is Gaussian to 6dB with 0.01dB ripple. To keep the group delay reasonably constant, the ripple should be small, most often between 0.001dB and 0.01dB.