# iirlp2hp

Transform lowpass IIR filter to highpass filter

## Description

`[`

transforms a lowpass IIR filter to a highpass IIR filter.`num`

,`den`

] = iirlp2hp(`b`

,`a`

,`wo`

,`wt`

)

The `iirlp2hp`

function returns the numerator and denominator
coefficients of the transformed highpass filter. The function accepts
`wo`

, frequency value to be transformed from the prototype
filter, and `wt`

, desired frequency in the transformed highpass
filter, and applies the lowpass to highpass frequency transformation on the input
prototype filter. The input prototype lowpass filter is specified with the numerator
and denominator coefficients, `b`

and `a`

respectively. For more details on the transformation, see IIR Lowpass to Highpass Frequency Transformation.

`[`

additionally returns the numerator and the denominator coefficients of the mapping
filter.`num`

,`den`

,`allpassNum`

,`allpassDen`

] =
iirlp2hp(`b`

,`a`

,`wo`

,`wt`

)

## 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.“Spectral transformations for digital filters.” *
Proceedings of the IEEE*, vol. 117, no. 8: 1585-1590. August
1970.

## Extended Capabilities

## Version History

**Introduced in R2011a**