www.pudn.com > matlab±à³Ì.zip > plot_filter.m, change:1999-03-08,size:1187b

%  Script file: plot_filter.m 
% 
%  Purpose:  
%    This program plots the amplitude and phase responses 
%    of a low-padd RC filter.  
% 
%  Record of revisions: 
%      Date       Programmer          Description of change 
%      ====       ==========          ===================== 
%    12/29/98    S. J. Chapman        Original code  
% 
% Define variables: 
%   amp       -- Amplitude response 
%   C         -- Capacitiance (farads) 
%   f         -- Frequency of input signal (Hz) 
%   phase     -- Phase response 
%   R         -- Resistance (ohms) 
%   res       -- Vo/Vi 
 
% Initialize R & C 
R = 16000;               % 16 k ohms 
C = 1.0E-6;              % 1 uF 
 
% Create array of input frequencies 
f = 1:2:1000; 
 
% Calculate response 
res = 1 ./ ( 1 + j*2*pi*f*R*C ); 
 
% Calculate amplitude response 
amp = abs(res); 
 
% Calculate phase response 
phase = angle(res); 
 
% Create plots 
subplot(2,1,1); 
loglog( f, amp ); 
title('Amplitude Response'); 
xlabel('Frequency (Hz)'); 
ylabel('Output/Input Ratio'); 
grid on; 
 
subplot(2,1,2); 
semilogx( f, phase ); 
title('Phase Response'); 
xlabel('Frequency (Hz)'); 
ylabel('Output-Input Phase (rad)'); 
grid on;