iirbpc2bpc

Transform IIR complex bandpass filter to IIR complex bandpass filter with different characteristics

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Syntax

[Num,Den,AllpassNum,AllpassDen] = iirbpc2bpc(B,A,Wo,Wt)

Description

[Num,Den,AllpassNum,AllpassDen] = iirbpc2bpc(B,A,Wo,Wt) transform IIR complex bandpass filter to IIR complex bandpass filter with different characteristics.

The iirbpc2bpc function returns the numerator and denominator vectors, Num and Den, respectively of the target filter transformed from the complex bandpass prototype by applying a first-order complex bandpass to complex bandpass frequency transformation. For more details, see IIR Complex Bandpass Frequency Transformation.

The function also returns the numerator, AllpassNum, and the denominator, AllpassDen, of the allpass mapping filter. The prototype lowpass filter is specified with the numerator B and a denominator A.

Frequencies must be normalized to be between -1 and 1, with 1 corresponding to half the sample rate.

example

Examples

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Open Live Script

Design a prototype real IIR lowpass elliptic filter with a gain of about –3 dB at 0.5π rad/sample.

[b,a] = ellip(3,0.1,30,0.409);

Create a complex passband from 0.25π to 0.75π.

[bc,ac] = iirlp2bpc(b,a,0.5,[0.25 0.75]);

Move the bandpass to between –0.3π and 0.1π.

[num,den] = iirbpc2bpc(bc,ac,[0.25 0.75],[-0.3 0.1]);

Compare the three filters.

hvft = filterAnalyzer(b,a,bc,ac,num,den,...
    FrequencyRange="centered",...
    FilterNames=["Prototype","PositiveComplexBand","Target"]);

Input Arguments

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Numerator of the prototype lowpass filter, specified as a row vector.

Data Types: single | double
Complex Number Support: Yes

Denominator of the prototype lowpass filter, specified as a row vector.

Data Types: single | double
Complex Number Support: Yes

Frequency values to be transformed from the prototype filter, specified as a two-element vector. Frequencies in Wo must be normalized to be between -1 and 1, with 1 corresponding to half the sample rate.

Data Types: single | double

Desired frequency locations in the transformed target filter, specified as a two-element vector. Frequencies in Wt must be normalized to be between -1 and 1, with 1 corresponding to half the sample rate.

Data Types: single | double

Output Arguments

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Numerator of the target filter, returned as a row vector.

Data Types: single | double
Complex Number Support: Yes

Denominator of the target filter, returned as a row vector.

Data Types: single | double
Complex Number Support: Yes

Numerator of the mapping filter, returned as a row vector.

Data Types: single | double
Complex Number Support: Yes

Denominator of the mapping filter, returned as a row vector.

Data Types: single | double

More About

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Version History

Introduced in R2011a

See Also

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