File mttroot/mtt/lib/control/PPP/ppp_butter.m artifact e0dda0f911 part of check-in 9997e50efa
function pol = ppp_butter (order,radius) ## usage: pol = cgpc_butter (order,radius) ## ## Butterworth polynomial of given order and pole radius ## Copyright (C) 1999 by P.J. Gawthrop ## $Id$ theta = pi/(2*order); # Angle with real axis even = (floor(order/2)==order/2); if even pol=1; N=order/2; else pol=[1 radius]; N=(order-1)/2; endif for i=1:N pol=conv(pol, [1 2*radius*cos(i*theta) radius^2]); endfor endfunction