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Polyphase decomposition of multirate filter


p = polyphase(hs)
p = polyphase(hs,Name,Value)


p = polyphase(hs) returns the polyphase matrix p of the multirate filter System object™ hs.

p = polyphase(hs,Name,Value) returns the polyphase matrix p of the multirate filter System object hs.

polyphase(hs) launches the Filter Visualization Tool (FVTool) with all the polyphase subfilters to allow you to analyze each component subfilter individually.

Input Arguments

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Filter System object.

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside single quotes (' '). You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

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For filter System object inputs only, specify the arithmetic used during analysis. When you specify 'double' or 'single', the function performs double- or single-precision analysis. When you specify 'fixed' , the arithmetic changes depending on the setting of the CoefficientDataType property and whether the System object is locked or unlocked.

 Details for Fixed-Point Arithmetic

When you do not specify the arithmetic for non-CIC structures, the function uses double-precision arithmetic if the filter System object is in an unlocked state. If the System object is locked, the function performs analysis based on the locked input data type. CIC structures only support fixed-point arithmetic.

Output Arguments


Polyphase matrix p of the multirate filter. Each row in the matrix represents one subfilter of the multirate filter. The first row of matrix p represents the first subfilter, the second row the second subfilter, and so on to the last subfilter.


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When you create a multirate filter that uses polyphase decomposition, polyphase lets you analyze the component filters individually by returning the components as rows in a matrix. First, create an interpolate-by-three filter.

hs = dsp.FIRInterpolator
hs = 

  dsp.FIRInterpolator with properties:

        NumeratorSource: 'Property'
              Numerator: [1×16 double]
    InterpolationFactor: 3

  Use get to show all properties

In this syntax, the matrix p contains all of the subfilters for hm, one filter per matrix row.

p = polyphase(hs)
p =

   -0.0013   -0.0107    0.1784    0.1784   -0.0107   -0.0013
   -0.0054    0.0204    0.2406    0.0904   -0.0124         0
   -0.0124    0.0904    0.2406    0.0204   -0.0054         0

Finally, using polyphase without an output argument opens the Filter Visualization Tool, ready for you to use the analysis capabilities of the tool to investigate the interpolator hm.


The fvtool shows the coefficients of the subfilters. To see the magnitude response of the subfilters, click on the Magnitude Response button on the fvtool toolstrip.

Introduced in R2011a

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