# dwtpassbands

DWT filter bank passbands

## Syntax

``dwtbands = dwtpassbands(fb)``

## Description

example

````dwtbands = dwtpassbands(fb)` returns the theoretical discrete wavelet transform (DWT) passbands for the DWT filter bank `fb`. ```

## Examples

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Obtain the theoretical DWT passbands for a four-level wavelet transform using the Daubechies `db6` wavelet with a sampling frequency of 1 kHz.

```wv = 'db6'; Fs = 1e3; fb = dwtfilterbank('Wavelet',wv,'Level',4,'SamplingFrequency',Fs); dwtpassbands(fb)```
```ans = 5×2 250.0000 500.0000 125.0000 250.0000 62.5000 125.0000 31.2500 62.5000 0 31.2500 ```

Obtain the power bandwidths for the filter bank. Compare the theoretical passbands with the measured wavelet 3 dB bandwidths at all four levels.

```ptable = powerbw(fb); ptable(:,1:3)```
```ans=4×3 table Level DWTBand Wavelet3dBBandwidth _____ ______________ ___________________ 1 250 500 250 500 2 125 250 123.2 253.71 3 62.5 125 61.601 126.78 4 31.25 62.5 30.815 63.389 ```

## Input Arguments

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Discrete wavelet transform (DWT) filter bank, specified as a `dwtfilterbank` object.

## Output Arguments

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Theoretical DWT passbands for the filter bank `fb`, returned as an L+1-by-2 real-valued matrix, where L is the wavelet transform level of the filter bank.

• The first L rows of `dwtbands` contain the theoretical passband frequencies for the DWT listed in order of decreasing resolution (increasing scale).

• The final row of `dwtbands` contains the theoretical passband for the coarsest resolution scaling filter.

• The first column of `dwtbands` contains the lower frequency limit.

• The final row of `dwtbands` contains the theoretical passband for the coarsest resolution scaling filter.

## Version History

Introduced in R2018a