In this applet a band pass equiripple filter for small number of extrema can be derived. In this case Fp1(56), Fp2(57) are the lower and upper cut off frequencies of the filter. Ft(58) is the width of the transition region, Te(59) is the total number of extrema, Pe(61) is the number of the extrema in the pass band, S1e(60) is the number of extrema in the lower stop band between 0 and Fp1(56) - Ft(58) and the number of extrema in the upper stop band is Te(59) - Pe(61) - S1e(60). In this applet changes should be made slowly.

The image below shows the filter obtained with the applet's starting parameters, pass band from 0.2 to 0.3, stop bands 0 to 0.12 and 0.38 to 0.5. The width of the transition region is 0.08. There are 8 extrema in each stop band and 7 in the pass band. The stop band attenuation is 71dB.

COPYRIGHT © 2008 Cuthbert Nyack.