# iir_butterord

Version:
Last Modified: March 15, 2017

Returns the order and natural frequency of the lowest order Butterworth filter with a given specification.

## Syntax

n = iir_butterord(wp, ws, dbp, dbs)
n = iir_butterord(wp, ws, dbp, dbs, domain)
[n, wn] = iir_butterord(wp, ws, dbp, dbs)
[n, wn] = iir_butterord(wp, ws, dbp, dbs, domain)
Legacy name: buttord

## wp

Passband frequency of the filter. wp is a nonnegative scalar in the interval [0, 1] or a vector of such numbers. If the output filter is analog, wp can be any positive number.

## ws

Stopband frequency of the filter. ws is a nonnegative scalar in the interval [0, 1] or a vector of such numbers. If the output filter is analog, ws can be any positive number.

## dbp

Decibel value of the passband. dbp is a real scalar.

## dbs

Decibel value of the stopband attenuation. dbs is a real scalar.

## domain

Specifies whether the output filter is digital or analog. domain is a string that accepts the following values:

Name Description
'z'

Returns the order and frequency of a digital filter.

's'

Returns the order and frequency of an analog filter.

Default: 'z'

## n

Filter order.

## wn

Natural frequency, or 3 dB frequency, of the filter.

% bandstop specification
WP = [0.1, 0.6];
WS = [0.3, 0.5];
DBP = 0.6;
DBS = 10;
[N, WN] = iir_butterord(WP, WS, DBP, DBS)

Where This Node Can Run:

Desktop OS: Windows

FPGA: This product does not support FPGA devices