The applet below shows a comparison of the frequency responses of low pass Chebyshev and Elliptic filters. The Chebyshev has only poles in the passband while the Elliptic has poles in the passband as well as zeros in the stopband. The Elliptic gives a faster increase in the attenuation after the cutoff frequency but has "rebounds" in the frequency response which the Chebyshev does not have.

In the applet below, both the Chebyshev and Elliptic approximations give an attenuation equal to the ripple at the cutoff frequency. n is specified for the Elliptic and the attenuation is calculated.

The magnitude response is shown as red-pink for the Elliptic and green-cyan for the Chebyshev.

COPYRIGHT © 2005 Cuthbert Nyack.