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iirftransf

IIR frequency transformation of filter

Syntax

[OutNum,OutDen] = iirftransf(OrigNum,OrigDen,FTFNum,FTFDen)

Description

[OutNum,OutDen] = iirftransf(OrigNum,OrigDen,FTFNum,FTFDen) returns the numerator and denominator vectors, OutNum and OutDen, of the target filter, which is the result of transforming the prototype filter specified by the numerator, OrigNum, and denominator, OrigDen, with the mapping filter given by the numerator, FTFNum, and the denominator, FTFDen. If the allpass mapping filter is not specified, then the function returns an original filter.

Examples

Design a prototype real IIR halfband filter using a standard elliptic approach:

[b, a] = ellip(3, 0.1, 30, 0.409);
[AlpNum, AlpDen] = allpasslp2lp(0.5, 0.25);
[num, den] = iirftransf(b, a, AlpNum, AlpDen);

Verify the result by comparing the prototype filter with the target filter:

fvtool(b, a, num, den);

Here's the comparison between the filters.

Arguments

VariableDescription
OrigNum

Numerator of the prototype lowpass filter

OrigDen

Denominator of the prototype lowpass filter

FTFNum

Numerator of the mapping filter

FTFDen

Denominator of the mapping filter

OutNum

Numerator of the target filter

OutDen

Denominator of the target filter

See Also

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