CLOGMAG

Purpose:

Evaluates the log magnitude squared frequency response of cascade form filter coefficients.

Syntax:

CLOGMAG(c, N, r)

(m, p) = CLOGMAG(c, N, r)

c	-	A series. The filter coefficients in cascade format.
N	-	Optional. An integer, the number of output samples. Defaults to 2048.
r	-	Optional. A real, the sample rate of the data. Defaults to rate of filter.

Returns:

A real series. The log magnitude squared frequency response of the filter.

(m, p) = CLOGMAG(c, N, r) returns both the log magnitude squared and phase response.

Example:

W1: elliptic(1,1000.0,200.0,3.0,40.0,250.0)

W2: clogmag(W1, 1024)

$image\clogmagpic.gif$

W1 contains the bi-quad cascade coefficients of an elliptical low pass filter. W2 contains 1024 uniformly spaced samples of the log magnitude squared frequency response of the filter in W1.

Remarks:

CLOGMAG employs ZFREQ to evaluate N uniformly spaced samples of the complex frequency response of the filter. The cascade coefficients are converted to direct form and the complex frequency response is evaluated using the FFT. The log magnitude squared of the complex frequency response is returned.

CLOGMAG is appropriate for computing the magnitude response of the IIR filters created by BESSEL, BUTTERWORTH, CHEBY1, CHEBY2 and ELLIPTIC filter design functions provided by DADiSP/Filters.

See CPHASE to compute the phase response of cascade form coefficients.