# iir_bessel (MathScript RT Module Function)

LabVIEW 2012 MathScript RT Module Help

Edition Date: June 2012

Part Number: 373123C-01

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Owning Class: filter design

Requires: MathScript RT Module

## Syntax

[b, a] = iir_bessel(n, w)

[b, a] = iir_bessel(n, [w1, w2])

[b, a] = iir_bessel(n, w, option)

[b, a] = iir_bessel(n, [w1, w2], 'stop')

[z, p, k] = iir_bessel(n, w)

[z, p, k] = iir_bessel(n, [w1, w2])

[z, p, k] = iir_bessel(n, w, option)

[z, p, k] = iir_bessel(n, [w1, w2], 'stop')

[as, bs, cs, ds] = iir_bessel(n, w)

[as, bs, cs, ds] = iir_bessel(n, [w1, w2])

[as, bs, cs, ds] = iir_bessel(n, w, option)

[as, bs, cs, ds] = iir_bessel(n, [w1, w2], 'stop')

Legacy Name: `besself`

## Description

Designs an analog Bessel filter. If you specify w, this function generates a lowpass filter of order n. If you specify w1 and w2, this function generates a bandpass filter of order 2n. [z, p, k] and [as, bs, cs, ds] generate the zero-pole-gain representation and the state-space representation, respectively, of the filter.

Examples

## Inputs

Name Description
n Specifies the filter order. n is a nonnegative integer.
w Specifies the cutoff frequency of the filter. w is a real number between 0 and 1. 1 represents the Nyquist frequency.
w1 Specifies the low cutoff frequency. w1 must fall in the range [0, 1].
w2 Specifies the high cutoff frequency. w2 must fall in the range [0, 1] and must be greater than w1.
option Specifies the type of filter to design. option is a string that accepts the following values.

 'low' (default) Designs a lowpass filter. 'high' Designs a highpass filter.
'stop' Directs LabVIEW to design a stopband filter. If you do not specify 'stop' and you specify w1 and w2, LabVIEW designs a bandpass filter.

## Outputs

Name Description
b Returns the numerator of the filter under design. b is the forward filter coefficient of order n. b is a real vector.
a Returns the denominator of the filter under design. a is the backward filter coefficient of order n. a is a real vector.
z Returns the zeros of the filter. z is a vector.
p Returns the poles of the filter. p is a vector.
k Returns the gain of the filter. k is a real number.
as Returns the A coefficients of the filter. as is a matrix.
bs Returns the B coefficients of the filter. bs is a matrix.
cs Returns the C coefficients of the filter. cs is a matrix.
ds Returns the D coefficients of the filter. ds is a matrix.

## Details

The following table lists the support characteristics of this function.

 Supported in the LabVIEW Run-Time Engine Yes Supported on RT targets Yes Suitable for bounded execution times on RT Not characterized

## Examples

N = 5;
W = 0.4;
[B, A] = iir_bessel(N, W)

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