phasez - Phase response of digital filter

Syntax

Description

[phi,w] = phasez(b,a,n) returns the n-point unwrapped phase response vector, phi, in radians and frequency vector, w, in radians/sample for the filter coefficients specified in b and a. The values of the frequency vector, w, range from 0 to pi. If n is omitted, the length of the phase response vector defaults to 512.

[phi,w]=phasez(Hd,n) returns the n-point unwrapped phase response vector, phi, in radians and frequency vector, w, in radians/sample for the discrete-time filter object Hd. If n is unspecified for discrete-time filter objects, the length of the phase response vector defaults to 8192.

[phi,w] = phasez(b,a,n,'whole') or [phi,w]=phasez(Hd,n,'whole') returns frequency and unwrapped phase response vectors evaluated at n equally-spaced points around the unit circle from 0 to 2*pi radians/sample.

phi = phasez(b,a,w) or phi=phasez(Hd,w) returns the unwrapped phase response in radians at frequencies specified in w (radians/sample). The frequencies are normally between 0 and pi.

[phi,f] = phasez(b,a,n,fs) and [phi,f]=phasez(Hd,n,fs) return the unwrapped phase vector phi in radians and the frequency vector in Hz. The frequency vector ranges from 0 to the Nyquist frequency, fs/2. If the 'whole' option is used, the frequency vector ranges from 0 to the sampling frequency.

phi = phasez(b,a,f,fs) and phi=phasez(Hd,f,fs) return the phase response in radians at the frequencies specified in the vector f (in Hz) using the sampling frequency fs (in Hz).

[phi,w,s] = phasez(...) and [phi,f,s] = phasez(...) return plotting information, where s is a structure array with fields you can change to display different frequency response plots.

phasez(b,a,...) or phasez(Hd) with no output arguments, plots the phase response of the filter. If the filter coefficients are inputted, the current figure window is used. If the user inputs a discrete-time filter object, fvtool is used to plot the phase response.

Examples

Example 1

Plot the phase response of a constrained least squares FIR filter:

b=fircls1(54,.3,.02,.008); 
phasez(b) 

Example 2

In the next example, we design an equiripple lowpass default filter object and display the result:

d=fdesign.lowpass;
Hd=design(d,'equiripple');
phasez(Hd)

Example 3

Plot the phase response of an elliptic filter:

d=fdesign.lowpass('Fp,Fst,Ap,Ast',0.4,0.5,1,60);
Hd=design(d,'ellip');
phasez(Hd)

See Also

freqz | fvtool | grpdelay | phasedelay

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