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butter

(/tools/hpmatlab/toolbox/signal/butter.m)

Function Synopsis

[num, den, z, p] = butter(n, Wn, ftype, anaflag)

Help text

BUTTER	Butterworth digital and analog filter design.
	[B,A] = BUTTER(N,Wn) designs an N'th order lowpass digital
	Butterworth filter and returns the filter coefficients in length
	N+1 vectors B and A.  The cut-off frequency Wn must be
	0.0 < Wn < 1.0, with 1.0 corresponding to half the sample rate.

	If Wn is a two-element vector, Wn = [W1 W2], BUTTER returns an 
	order 2N bandpass filter with passband  W1 < W < W2.
	[B,A] = BUTTER(N,Wn,'high') designs a highpass filter.
	[B,A] = BUTTER(N,Wn,'stop') is a bandstop filter if Wn = [W1 W2].
	
	When used with three left-hand arguments, as in
	[Z,P,K] = BUTTER(...), the zeros and poles are returned in
	length N column vectors Z and P, and the gain in scalar K. 

	When used with four left-hand arguments, as in
	[A,B,C,D] = BUTTER(...), state-space matrices are returned.

	BUTTER(N,Wn,'s'), BUTTER(N,Wn,'high','s') and BUTTER(N,Wn,'stop','s')
	design analog Butterworth filters.  In this case, Wn can be bigger
	than 1.0.

	See also BUTTORD, BESSELF, CHEBY1, CHEBY2, ELLIP, FREQZ and FILTER.

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Produced by mat2html on Wed Feb 8 12:25:18 EST 1995
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