This applet enables the study of low pass filters with the Kaiser window. The effect of N, q and n on the filter characteristics can be examined.

eg parameters (31, 0.15, 2.0, 0.55, NA, -65, -80, 69, 171, 2) has a 0.1dB to 80dB bandwidth of ~0.228 - 0.092 = ~0.136w

With N = 91, q = 1p, n = 0.5 the minimum stop band attenuation is ~39dB. Increasing q to 3.5p increases the minimum stop band attenuation to 109dB. dB/q ~ 8.9 and dBp/q ~28. These numbers are only a rough approximation.

The image below show a low pass filter with a minimum stop band attenuation of 100dB. The filter length is 91 and the 0.1dB to 100dB transition bandwidth is ~0.061w

First line:-

The white frequency reference line is at 0.198w

Second line:-

The frequency of the Orange frequency reference line is 0.137w

Third line:-

When k = 2 the impulse responses I(k) for the standard Kaiser, variable Kaiser and Rectangular window are -2.4274211E-5, -1.9789742E-5 and -5.0673979E-3.

Changing fc/fs to 0.161 and q/ p to 3.21 gives similar charactreistics for the standard Kaiser window but the stop band response is not as flat.

COPYRIGHT © 2008 Cuthbert Nyack.