www.gusucode.com > signal 工具箱matlab源码程序 > signal/+fspecs/@lpcutoffwap/cheby1.m
function Hd = cheby1(this, varargin) %CHEBY1 Chebyshev Type I digital filter design. % Author(s): J. Schickler % Copyright 1988-2005 The MathWorks, Inc. N = this.FilterOrder; nfreq = this.NormalizedFrequency; normalizefreq(this, true); Fc = this.F3dB; normalizefreq(this, nfreq); Ap = this.Apass; % Compute analog frequency Wc = tan(pi*Fc/2); % Find corresponding analog passband-edge frequency Wp = Wc/cosh(1/N*acosh(1/sqrt(10^(Ap/10)-1))); % Convert analog passband-edge frequency to digital Fp = 2*atan(Wp)/pi; % Convert to lowpass with passband-edge specifications hs = fspecs.lppass(N,Fp,Ap); Hd = cheby1(hs,varargin{:}); % [EOF]