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step

System object: dsp.DyadicAnalysisFilterBank
Package: dsp

Decompose input with dyadic filter bank

Syntax

Y = step(H,X)

Description

    Note:   Starting in R2016b, instead of using the step method to perform the operation defined by the System object™, you can call the object with arguments, as if it were a function. For example, y = step(obj,x) and y = obj(x) perform equivalent operations.

Y = step(H,X) computes the subband decomposition of the input X and outputs the dyadic subband decomposition in Y as a single concatenated column vector or matrix of coefficients. Each column of X is treated as an independent input, and the number of rows of X must be a multiple of 2N, where N is the value of the NumLevels property. The elements of Y are ordered with the highest frequency subband first followed by subbands in decreasing frequency

Examples

Subband ordering for level-two asymmetric tree structure:

t = 0:.001:1.023; 
% Sampling frequency 1 kHz input length 1024
x= square(2*pi*30*t);
xn = x' + 0.08*randn(length(x),1);
% Default asymmetric structure with
% Daubechies order 3 extremal phase wavelet
H = dsp.DyadicAnalysisFilterBank;
Y = step(H,xn);
% Level 2 yields 3 subbands (two detail-one approximation)
% Nyquist frequency is 500 Hz
D1 =Y(1:512); % subband approx. [250, 500] Hz 
D2 = Y(513:768); % subband approx. [125, 250] Hz
Approx = Y(769:1024); % subband approx. [0,125] Hz

Subband ordering for symmetric tree structure:

t = 0:.001:1.023; 
% Sampling frequency 1 kHz input length 1024
x= square(2*pi*30*t);
xn = x' + 0.08*randn(length(x),1); % symmetric structure with
% Daubechies order 3 extremal phase wavelet
H = dsp.DyadicAnalysisFilterBank('TreeStructure',...
'Symmetric');
Y = step(H,xn);
D1 = Y(1:256); % subband approx. [375,500] Hz
D2 = Y(257:512); % subband approx. [250,375] Hz
D3 = Y(513:768); % subband approx. [125,250] Hz
Approx = Y(769:1024); % subband approx. [0, 125] Hz
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