Programmer Guide/Command Reference/EVAL/iir1

iir1

An Infinite Impulse Response (IIR) filter.

Usage:

iir1(f1, f2, m, rp, rs, inv, type)

Function:

Computes the filter coefficients for an IIR filter with cutoff frequencies f1 and f2 and the order m.

Parameters:

f1

The rel. lower cutoff frequency.

f2

The rel. upper cutoff frequency (0 <= f1 < f2 <= 0.5).

m

The filter order (m >= 2). The default is 3.

rp

The passband riple in dB (rp > 0). The default is 0.5.

rs

The stopband damping in dB (rs > 0). The default is 40.

inv

The invert frequency response (0|1). The default is 0.

type

The type of filter to use. The following values are supported:

1 A Butterworth filter

2 A Chebyshev filter

3 An elliptic filter (This is the default).

Result:

A matrix c with 2 columns:

(c[*,0] = poles, c[*,1] = zeros)

Usage:

iir1(f1, f2, m, rp, rs, inv, type, x)

Function:

Computes the filter coefficients for an IIR filter with cutoff frequencies f1 and f2 and the order m and apply it to the signal x.

Parameters:

x

A signal vector.

For all other parameters see irr1 above.

Result:

A filtered signal of the same type as x.