ctfirstorderfilter.m

很多matlab的源代码

function [f, h] = ctfirstorderfilter(type, cutoff, bandwidth)
% CTFIRSTORDERFILTER implements continuous time filters, to be used with 
% cltidemo. 
%   [f, h] = ctfirstorderfilter(type, cutoff, bandwidth)
% where, 
%   type   - can be one of 'Lowpass', 'Highpass', 'Bandpass' or 'Bandreject'
%   cutoff - is the cutoff frequency in Hz. (Max - 200 Hz)
%   bandwidth - for Bandpass and Bandreject filters ( 10 to 50 Hz)
%

  f = linspace(0,200,1001);
  fc = cutoff ;
  % Bandpass filter - Bandwidth
  bw = bandwidth;
  
  switch type
   case 'Lowpass'
    for i=1:length(f)
      h(i) = 1/(1+j*f(i)/fc);
    end
   case 'Highpass'
    for i=1:length(f)
      h(i) = (j*f(i)/fc)/(1+j*f(i)/fc);
    end
   case 'Bandpass'
    for i=1:length(f)
      h(i) = (j*f(i)*bw)/(f(i)^2 - fc^2 + j*f(i)*bw);
    end
   case 'Bandreject'
    for i=1:length(f)
      h(i) = (f(i)^2 - fc^2)/(f(i)^2 - fc^2 + j*f(i)*bw);
    end
   otherwise
    error 'Filter type unknown or unspecified'
  end
  
% endfunction ctfirstorderfilter

% eof: ctfirstorderfilter.m