# polyphase

Return polyphase matrix

## Syntax

``p = polyphase(obj)``

## Description

example

````p = polyphase(obj)` returns the polyphase matrix used by the filter bank in `dsp.Channelizer` and `dsp.ChannelSynthesizer` System objects. Each row in the matrix corresponds to a polyphase branch. The number of columns in `p` corresponds to the number of filter taps per branch.```

## Examples

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Compute the polyphase matrix of the filter bank used by the channelizer.

Design a channelizer with the number of frequency bands or polyphase branches set to 8, the number of taps or coefficients per band set to 12, and stopband attenuation set to 80 dB.

```channelizer = dsp.Channelizer; p = polyphase(channelizer)```
```p = 8×12 0 0 0 0 0 0 0.1250 0 0 0 0 0 -0.0000 0.0002 -0.0007 0.0022 -0.0056 0.0161 0.1216 -0.0119 0.0045 -0.0017 0.0005 -0.0001 -0.0000 0.0004 -0.0015 0.0045 -0.0117 0.0354 0.1118 -0.0192 0.0073 -0.0027 0.0008 -0.0001 -0.0001 0.0006 -0.0023 0.0067 -0.0172 0.0565 0.0966 -0.0220 0.0085 -0.0031 0.0009 -0.0001 -0.0001 0.0008 -0.0029 0.0082 -0.0210 0.0776 0.0776 -0.0210 0.0082 -0.0029 0.0008 -0.0001 -0.0001 0.0009 -0.0031 0.0085 -0.0220 0.0966 0.0565 -0.0172 0.0067 -0.0023 0.0006 -0.0001 -0.0001 0.0008 -0.0027 0.0073 -0.0192 0.1118 0.0354 -0.0117 0.0045 -0.0015 0.0004 -0.0000 -0.0001 0.0005 -0.0017 0.0045 -0.0119 0.1216 0.0161 -0.0056 0.0022 -0.0007 0.0002 -0.0000 ```

Each row in the matrix corresponds to a polyphase branch. The number of columns in the matrix corresponds to the number of filter taps per branch.

## Input Arguments

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Input filter, specified as either a `dsp.Channelizer` or `dsp.ChannelSynthesizer` System object.

Example: channelizer = dsp.Channelizer;

Example: ```channelizer = dsp.ChannelSynthesizer```

## Output Arguments

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Polyphase matrix of the filter bank, returned as a matrix of size [NFBands, NTPerBand]. The dimensions of the matrix depend on the type of System object in the `obj` argument:

• `dsp.Channelizer` –– NFBands is the value you specify in the `NumFrequencyBands` property, and NTPerBand is the value you specify in the `NumTapsPerBand` property.

• `dsp.ChannelSynthesizer` –– NFBands is the number of narrowband signals or the number of columns in the input signal, and NTPerBand is the value you specify in the `NumTapsPerBand` property.

## Version History

Introduced in R2016b