Comparison of Equiripple Approximation and Kaiser Window.

Cuthbert Nyack
Here FIR filters derived from the equiripple approximation and the Kaiser Window are compared.

In the applet below, the parameters controlling the frequency response of the filter with the Kaiser window are controlled by the variables shown on the lower left. N is the length of the window filter, fc/fs is the cut off frequency, q/p and 'n' are variable parameters of the Kaiser window.
For the equiripple case Ntap is the length of the filter and RR(62) is the ratio of the pass band to the stop band ripple.

The 2 images below show the difference between the 2 approximations increase as the transition bandwidth is reduced.

Below, the same cases are compared with the pass band ripple equal to the stop band ripple. The difference has been reduced.

Below the 2 filters have the same length. The transition bandwidth has increased to 0.09 and the ratio of pass band to stop band ripple has been reduced to 0.1.

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COPYRIGHT 2008 Cuthbert Nyack.