firlpp.m

很多matlab的源代码

function [wp,ws,w0]=firlpp(ty,fp,fs,ff)
% FIRLPP conversion to LPP for FIR filter design.
% This is a support file for FIRWIND, FIRHB, FIRPM


% ADSP Toolbox: Version 2.0 
% For use with "Analog and Digital Signal Processing", 2nd Ed.
% Published by PWS Publishing Co.
%
% Ashok Ambardar, EE Dept. MTU, Houghton, MI 49931, USA
% http://www.ee.mtu/faculty/akambard.html
% e-mail: [e-mail]
% Copyright (c) 1998


%NOTE: Change pi to 0.5 (for HP) if routine is changed to input fp,fs in Hz

w0=[];wp=fp/ff;ws=fs/ff;if ty=='lp',return,end
lp=length(wp);ls=length(ws);
if ty=='hp',if lp>1 | ls>1,error('Too many frequencies')
else,wp=pi-wp;ws=pi-ws;return,end,end
if lp<2 | ls<2,error('too few frequencies'),return,end
ap=abs(diff(fp));as=abs(diff(fs));
if ty=='bs',if ap<=as,error('passband & stopband switched'),return,end,end
if ty=='bp',if as<=ap,error('passband & stopband switched'),return,end,end
dw1=abs(wp(1)-ws(1));dw2=abs(wp(2)-ws(2));dw=min(dw1,dw2);
if ty=='bp',w0=.5*(wp(1)+wp(2));wp=.5*(wp(2)-wp(1));
else,w0=.5*(ws(1)+ws(2));wp=.5*(ws(2)-ws(1));end
ws=wp+dw;