# iirlp2bp

Transform IIR lowpass filter to IIR bandpass filter

## Description

`[`

transforms an IIR lowpass filter to an IIR bandpass filter.`num`

,`den`

,`allpassNum`

,`allpassDen`

] =
iirlp2bp(`b`

,`a`

,`wo`

,`wt`

)

The `iirlp2bp`

function returns the numerator and denominator
coefficients of the transformed bandpass filter. The function transforms the real
lowpass prototype filter, specified by the numerator coefficients
`b`

and denominator coefficients `a`

, by
applying a second-order real lowpass to real bandpass frequency mapping. For more
information, see IIR Lowpass to IIR Bandpass Transformation.

The function also returns the numerator and the denominator coefficients of the
allpass mapping filter, `allpassNum`

and
`allpassDen`

respectively.

Frequencies must be normalized to be between 0 and 1, with 1 corresponding to half the sample rate.

## Examples

## Input Arguments

## Output Arguments

## More About

## References

[1] Nowrouzian, B., and A.G.
Constantinides. “Prototype Reference Transfer Function Parameters in the Discrete-Time
Frequency Transformations.” In *Proceedings of the 33rd Midwest
Symposium on Circuits and Systems*, 1078–82. Calgary, Alta., Canada: IEEE,
1991. https://doi.org/10.1109/MWSCAS.1990.140912.

[2] Nowrouzian, B., and L.T.
Bruton. “Closed-Form Solutions for Discrete-Time Elliptic Transfer Functions.” In [1992]
*Proceedings of the 35th Midwest Symposium on Circuits and
Systems*, 784–87. Washington, DC, USA: IEEE, 1992.
https://doi.org/10.1109/MWSCAS.1992.271206.

[3] Constantinides, A.G. “Design
of Bandpass Digital Filters.” *Proceedings of the IEEE*
57, no. 6 (1969): 1229–31. https://doi.org/10.1109/PROC.1969.7216.

[4] Constantinides,
A.G.“Spectral transformations for digital filters.” *
Proceedings of the IEEE*, vol. 117, no. 8: 1585-1590. August
1970.

## Extended Capabilities

## Version History

**Introduced in R2011a**