IEEE文章仿真FIR滤波器,附带源代码程序,便于理解与深入学习.

				function [b,a] = cheby2_3db(N,Fc,Ast)
				% CHEBY2_3DB Design a lowpass Chebyshev Type II filter given a 3 dB point.
				%   Inputs:
				%       N   - Filter order
				%       Fc  - 3 dB cutoff frequency (0 to 1)
				%       Ast - Stopband attenuation (dB)
				%
				%   NOTE 1: This function requires the Signal Processing Toolbox.
				%
				%   NOTE 2: To design highpass, bandpass, and bandstop filters use the
				%   resulting filter from this function along with IIRLP2HP, IIRLP2BP, and
				%   IIRLP2BS respectively. These functions are included in the Filter
				%   Design Toolbox.
				%
				%   % Example 6th order filter with cutoff at 0.3:
				%   [b,a] = cheby2_3db(6,.3,80);
				%   fvtool(b,a)
				
				%   Author(s): V. Pellissier, R. Losada
				%   Copyright 2005 The MathWorks, Inc.
				
				% Compute cutoff frequency of analog lowpass filter
				Wc = tan(pi*Fc/2); 
				
				% Find corresponding analog stopband-edge frequency
				est = sqrt(10^(Ast/10)-1); % Convert to non-dB
				Wst = Wc*cosh(1/N*acosh(est));
				
				% Convert analog stopband-edge frequency to digital
				Fst = 2*atan(Wst)/pi;
				
				% Use classic design technique
				[b,a] = cheby2(N,Ast,Fst);