zerophase - Zero-phase response for filter

Syntax

zerophase(ha)
[hr,w] = zerophase(ha,n)
[hr,w] = zerophase(...,f)
zerophase(hd)
[hr,w] = zerophase(hd,n)
[hr,w] = zerophase(...,f)
zerophase(hm)
[hr,w] = zerophase(hm,n)
[hr,w] = zerophase(...,f)
[hr,w] = zerophase(...,fs)

Description

The next sections describe common zerophase operation with adaptive, discrete-time, and multirate filters. For more input options, refer to zerophase in Signal Processing Toolbox documentation.

Adaptive Filters

For adaptive filters, zerophase returns the instantaneous zero-phase response based on the current filter coefficients.

zerophase(ha) displays the zero-phase response of ha in the Filter Visualization Tool (FVTool).

[hr,w] = zerophase(ha,n) returns length n vectors hr and w containing the instantaneous zero-phase response of the adaptive filter ha, and the frequencies in radians at which zerophase evaluated the response. The zero-phase response is evaluated at n points equally spaced around the upper half of the unit circle. For an FIR filter where n is a power of two, the computation is done faster using FFTs. If n is not specified, it defaults to 8192.

[hr,w] = zerophase(ha) returns a matrix hr if ha is a vector of filters. Each column of the matrix corresponds to each filter in the vector. If you provide a row vector of frequency points f as an input argument, each row of hr corresponds to one filter in the vector.

Discrete-Time Filters

zerophase(hd) displays the zero-phase response of hd in the Filter Visualization Tool (FVTool).

[hr,w] = zerophase(hd,n) returns length n vectors hr and w containing the instantaneous zero-phase response of the adaptive filter hd, and the frequencies in radians at which zerophase evaluated the response. The zero-phase response is evaluated at n points equally spaced around the upper half of the unit circle. For an FIR filter where n is a power of two, the computation is done faster using FFTs. If n is not specified, it defaults to 8192.

[hr,w] = zerophase(hd) returns a matrix hr if hd is a vector of filters. Each column of the matrix corresponds to each filter in the vector. If you provide a row vector of frequency points f as an input argument, each row of hr corresponds to one filter in the vector.

Multirate Filters

zerophase(hm) displays the zero-phase response of hd in the Filter Visualization Tool (FVTool).

[hr,w] = zerophase(hm,n) returns length n vectors hr and w containing the instantaneous zero-phase response of the adaptive filter hm, and the frequencies in radians at which zerophase evaluated the response. The zero-phase response is evaluated at n points equally spaced around the upper half of the unit circle. For an FIR filter where n is a power of two, the computation is done faster using FFTs. If n is not specified, it defaults to 8192.

[hr,w] = zerophase(hm) returns a matrix hr if hm is a vector of filters. Each column of the matrix corresponds to each filter in the vector. If you provide a row vector of frequency points f as an input argument, each row of hr corresponds to one filter in the vector.

Note that the response is computed relative to the rate at which the filter is running. If a sampling frequency is specified, it is assumed that the filter is running at that rate.

Note that the multirate filter delay response is computed relative to the rate at which the filter is running. When you specify fs (the sampling rate) as an input argument, zerophase assumes the filter is running at that rate.

For multistage cascades, zerophase forms a single-stage multirate filter that is equivalent to the cascade and computes the response relative to the rate at which the equivalent filter is running. zerophase does not support all multistage cascades. Only cascades for which it is possible to derive an equivalent single-stage filter are allowed for analysis.

As an example, consider a two-stage interpolator where the first stage has an interpolation factor of 2 and the second stage has an interpolation factor of 4. An equivalent single-stage filter with an overall interpolation factor of 8 can be found. zerophase uses the equivalent filter for the analysis. If a sampling frequency fs is specified as an input argument to zerophase, the function interprets fs as the rate at which the equivalent filter is running.