File:Phase Plots.svg

Made by Ugur Zongur using GNU Octave and Gnuplot in order to demonstrate linearity or non-linearity of phase plots of various filters.

GNU Octave Code:

% Phase Demonstration of basic Filters % Written By: Ugur Zongur

a=[1 1 1 1]; % Symmetrical (So this has got Linear Phase) [pp_1,w] = freqz(a,1);

a=[1 1 -1 -1]; % Symmetrical (So this has got Linear Phase) [pp_2,w] = freqz(a,1);

a=[1 2]; % Numerator b=[3 4]; % Denominator [pp_3,w] = freqz(a,b);

a=[4 3 2 1]; % Not Symmetrical (So this hasn't got Linear Phase) [pp_4,w] = freqz(a,1);

data = [w/pi ; arg(pp_1); arg(pp_2); arg(pp_3); arg(pp_4)]';

save -ascii 'Phase_Plots.dat' data;

Gnuplot Code:

1. set the output

set terminal svg set output "Phase_Plots.svg"

1. axis properties

set xrange [0:1] set key off

1. Set up a four-pane multiplot

set size 1, 1 set origin 0, 0 set multiplot

set title "a) FIR Filter (Type II) having Linear Phase" set size 0.5,0.5 set origin 0 , 0.5 plot "Phase_Plots.dat" using 1:2 with lines linewidth 2

set title "b) FIR Filter (Type IV) having Linear Phase" set size 0.5, 0.5 set origin 0.5 , 0.5 plot "Phase_Plots.dat" using 1:3 with lines linewidth 2

set title "c) IIR Filter having Non-Linear Phase" set size 0.5, 0.5 set origin 0 , 0 plot "Phase_Plots.dat" using 1:4 with lines linewidth 2

set title "d) FIR Filter having Non-Linear Phase" set size 0.5, 0.5 set origin 0.5 , 0 plot "Phase_Plots.dat" using 1:5 with lines linewidth 2

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