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Transform IIR lowpass filter to IIR complex N-point filter

`[`

transform
IIR lowpass filter to IIR complex N-point filter.`Num`

,`Den`

,`AllpassNum`

,`AllpassDen`

] =
iirlp2xc(`B`

,`A`

,`Wo`

,`Wt`

)

The `iirlp2xc`

function returns the numerator and denominator
vectors, `Num`

and `Den`

respectively, of the
target filter transformed from the real lowpass prototype by applying an
`N`

-order real lowpass to
complex multipoint frequency transformation. For more details, see IIR Lowpass Filter to IIR Complex N-Point Filter Transformation.^{th}

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
denominator `A`

.

[1] Krukowski, A., and I. Kale,
“High-order complex frequency transformations,” *Internal report
No. 27/2001*, Applied DSP and VLSI Research Group, University of
Westminster.