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
| Variable | Description |
|---|---|
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 |