polyphase

Return polyphase matrix

Syntax

p = polyphase(obj)

Description

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

Polyphase Matrix of Filter Bank

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

obj — Input filter System object™

dsp.Channelizer | dsp.ChannelSynthesizer

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

Example: channelizer = dsp.Channelizer;

Example: channelizer = dsp.ChannelSynthesizer

Output Arguments

p — Polyphase matrix

matrix

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.