www.gusucode.com > signal 工具箱matlab源码程序 > signal/+fspecs/@lpcutoffwfp/cheby1.m
function Hd = cheby1(this, varargin) %CHEBY1 Chebyshev Type I digital filter design. % Copyright 1988-2012 The MathWorks, Inc. N = this.FilterOrder; nfreq = this.NormalizedFrequency; normalizefreq(this, true); Fc = this.F3dB; Fp = this.Fpass; normalizefreq(this, nfreq); [isvalid, errmsg, errid] = checkincfreqs(this,{'Fpass','F3dB'}); if ~isvalid error(message(errid,errmsg)); end % Compute analog frequency Wc = tan(pi*Fc/2); % Determine analog passband edge frequency Wp = tan(pi*Fp/2); % Find epass, Apass ep = 1/cosh(N*acosh(Wc/Wp)); Ap = 10*log10(ep^2+1); % Convert to lowpass with passband-edge specifications hs = fspecs.lppass(N,Fp,Ap); Hd = cheby1(hs,varargin{:});