# zerophase

Zero-phase response of digital filter

## Syntax

## Description

`[`

returns the zero-phase response of the specified digital filter. Specify a digital filter
with numerator coefficients `Hr`

,`w`

] = zerophase(`b`

,`a`

)`b`

and denominator coefficients
`a`

. The function evaluates the zero-phase response at 512 equally
spaced points on the upper half of the unit circle, and returns the zero-phase response
`Hr`

with the corresponding angular frequencies
`w`

.

`[`

returns the zero-phase response of the digital filter represented as Cascaded Transfer Functions (CTF) with numerator coefficients `Hr`

,`w`

] = zerophase(`B,A`

,"ctf")`B`

and denominator coefficients
`A`

.* (since R2024b)*

`[`

returns the zero-phase response for the digital filter `Hr`

,`w`

] = zerophase(`d`

)`d`

. Use `designfilt`

to generate `d`

based on frequency-response
specifications.

`zerophase(___)`

plots the
zero-phase response versus frequency. If you input the filter coefficients or second order
sections matrix, the function plots in the current figure window.

**Note**

If the input to `zerophase`

is single precision, the function
calculates the zero-phase response using single-precision arithmetic. The output
`Hr`

is single precision.

## Examples

## Input Arguments

## Output Arguments

## More About

## Tips

## References

[1] Antoniou, Andreas.
*Digital Filters*. New York: McGraw-Hill, Inc.,
1993.

[2] Lyons, Richard G. *Understanding Digital Signal Processing*. Upper
Saddle River, NJ: Prentice Hall, 2004.

## Version History

**Introduced before R2006a**

## See Also

### Apps

### Functions

`ctffilt`

|`designfilt`

|`digitalFilter`

|`freqs`

|`freqz`

|`grpdelay`

|`invfreqz`

|`phasedelay`

|`phasez`