# powerbw

DWT filter bank power bandwidth

## Syntax

## Description

returns a MATLAB`bwtable`

= powerbw(`fb`

)^{®} table `bwtable`

containing the theoretical and
measured bandwidths of the discrete wavelet transform (DWT) filter bank
`fb`

. The table contains the following variables by level:

DWT frequency bands

Measured wavelet and scaling filter 3 dB bandwidths

Proportions of the total energy in the reported bands

## Examples

### DWT Filter Bank Power Bandwidth

Obtain the 3 dB bandwidths of a level-4 discrete wavelet transform with the Fejér-Korovkin `fk18`

wavelet. Obtain the frequency responses of the wavelets. Plot the one-sided frequency responses for the wavelet filters.

fb = dwtfilterbank('Wavelet','fk18','Level',4); bw = powerbw(fb); [psidft,f] = freqz(fb); freqz(fb)

Choose the wavelet bandpass filter whose peak magnitude is equal to 2. Obtain the lower and upper bounds of the 3 dB bandwidth of the filter.

wv = 2; wvBw = bw.Wavelet3dBBandwidth(wv,:);

Plot the magnitude frequency response of the filter and the 3 dB limits. Since the frequency response has a maximum value equal to 2, confirm the lower and upper frequency bounds intersect the frequency response at $$\sqrt{2}$$.

filLength = size(psidft,2); plot(f(filLength/2+1:end),abs(psidft(wv,filLength/2+1:end))) hold on plot([wvBw(1) wvBw(1)],[0 2],'r') plot([wvBw(2) wvBw(2)],[0 2],'r') grid on title(['Proportion of Wavelet Power in 3 dB Band: ',num2str(bw.WaveletPowerIn3dBBand(wv))]) xlabel('Normalized Frequency (cycles/sample)') ylabel('Magnitude')

## Input Arguments

`fb`

— Discrete wavelet transform filter bank

`dwtfilterbank`

object

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

object.

## Output Arguments

`bwtable`

— Theoretical and measured bandwidths

table

Theoretical and measured bandwidths of the DWT filter bank
`fb`

, returned as a MATLAB table. `bwtable`

is
*L*-by-8, where *L* is the wavelet
transform level of the filter bank. Levels are ordered by decreasing
resolution. `bwtable`

has the following eight
variables:

`Level`

— Level of DWT decomposition

positive integer

Level of DWT decomposition, returned as a positive integer.

`DWTBand`

— Theoretical DWT frequency bands

two-element real-valued vector

Theoretical DWT frequency bands by level, returned as a two-element real-valued vector.

`Wavelet3dBBandwidth`

— Measured wavelet 3 dB bandwidths

two-element real-valued vector

Measured wavelet 3 dB bandwidths by level, returned as a two-element real-valued vector.

`Scaling3dBBandwidth`

— Measured scaling filter 3 dB bandwidths

two-element real-valued vector

Measured scaling filter 3 dB bandwidths by level, returned as a two-element real-valued vector.

`WaveletPowerIn3dBBand`

— Proportion of total wavelet power

positive scalar

Proportion of total wavelet power in the measured 3 dB band by level, returned as a positive scalar.

`ScalingPowerIn3dBBand`

— Proportion of total scaling filter power

positive scalar

Proportion of total scaling filter power in the measured 3 dB band by level, returned as a positive scalar.

`WaveletPowerInDWTBand`

— Proportion of total wavelet power

positive scalar

Proportion of total wavelet power in the theoretical DWT band by level, returned as a positive scalar.

`ScalingPowerInDWTBand`

— Proportion of total scaling filter power

positive scalar

Proportion of total scaling filter power in the theoretical DWT band by level, returned as a positive scalar.

## Version History

**Introduced in R2018a**

## See Also

## MATLAB 명령

다음 MATLAB 명령에 해당하는 링크를 클릭했습니다.

명령을 실행하려면 MATLAB 명령 창에 입력하십시오. 웹 브라우저는 MATLAB 명령을 지원하지 않습니다.

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