bug

yakup murat mert ymmert at yahoo.com
Sun May 11 13:49:23 CDT 2008


octave 3.0.0 gives the following error for the code given below error ...However code still works..

error: cant  perform indexing operstions for <unknown type > type

(gnuplot.exe:1272) : Pango warning : couldnt load font "helvetice not rotated 200 " falling back to "sans not-rotated 200 "  expect ugly output

Code: ----------------------------------------------

% Example 5-3 p 229:  Butterworth Low-Pass Filter 
% 
 
close all; % close all opened graphs 
clear all; % clear all variables 
figure;    % open new graph 
 
% Normalized components from filter coefficient tables 
Ln1 = 1.;  %  Normalized Inductance 
Ln2 = 1.;  %  Normalized Inductance  
Cn1 = 2.;  %  Normalized Capacitance 
Rg = 50;    % Source resistance 
RL = 50;     % Load Resistance 
 
wc=2*pi*900e6;  % Cutoff Frequency of 900 MHz 
 
L1=Ln1*RL/wc;  %  Actual L1 value 
L2=Ln2*RL/wc;  %  Actual L2 value 
C1=Cn1/(RL*wc);  %  Actual C1 value 
 
f = 1; 
for i=1:4000; 
  w=2*pi*f;   
  ZL1=j*w*L1; 
  ZL2=j*w*L2; 
  ZC1=1./(j*w*C1);  
  YC1=1./ZC1; 
  GL=1./RL;  
 
  % Define the ABCD matrices for each element of the filter 
 
  A0=[1 Rg;0 1]; 
  A1=[1 ZL1;0 1]; 
  A2=[1 0;YC1 1]; 
  A3=[1 ZL2;0 1]; 
  A4=[1 0;GL 1]; 
 
  ABCD=A0*A1*A2*A3*A4;  
  freq(i)=f; 
  H(i)=2.*1/(ABCD(1));  
 
  f=f+0.001*wc/(2*pi); 
end 
 
subplot(211), semilogx(freq,20*log10(abs(H)));grid on; ylim([-50 10]); 
title('Low-Pass Butterworth Filter Response');  
xlabel('Frequency, Hz'); 
ylabel('Attenuation, dB');  
 
phase=atan(imag(H)./real(H));  
subplot(212), semilogx(freq,phase/pi*180);grid on; 
xlabel('Frequency, Hz'); 
ylabel('Phase, deg.'); 

       
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