CPHASE

Purpose:

Evaluates the phase response of cascade form filter coefficients.

Syntax:

CPHASE(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 phase response of the filter in radians.

Example:

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

W2: cphase(W1, 1024)

$image\cphasepic.gif$

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

Remarks:

CPHASE 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 phase of the complex frequency response is returned.

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

See CLOGMAG to compute the magnitude response of cascade form coefficients.