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File:In-phase and quadrature components of angle modulation.gif

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Summary

Description
English: Graphic example of the formula The phase modulation (φ(t), not shown) is a non-linearly increasing function from 0 to over the interval 0 < t < 16. The two amplitude-modulated components are known as the in-phase component (I, thin blue, decreasing) and the quadrature component (Q, thin red, increasing).

Alternative description:

Example of how an angle-modulated sinusoid can be decomposed into or synthesized from two amplitude-modulated sinusoids. The picture shows a modulation by non-linearly increasing the phase angle of the carrier from 0 to over the interval 0 < t < 16. The two AM sinusoids have the same nominal frequency as the carrier and are offset in phase by one-quarter cycle ( radians). They are known as the in-phase component (I, thin blue, decreasing) and the quadrature component (Q, thin red, increasing). In some contexts it is more convenient to refer to just the enveloping factors of the AM-signals (thick red and blue lines) by those component terms.
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Source Own work
Author Bob K
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I, the copyright holder of this work, hereby publish it under the following license:
Creative Commons CC-Zero This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication.
The person who associated a work with this deed has dedicated the work to the public domain by waiving all of their rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.

GIF development
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N
 
This GIF graphic was created with GNU Octave.
Octave/gnuplot source
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click to expand

This graphic was created by the following Octave script:

graphics_toolkit gnuplot

N = 500;                        %length of plot
sams = 0:N;

cycles = 0.25;                  % 1/4 cycle of phi(t)
cyc_per_sam = cycles/N;
phi = pi/2 * sin(2*pi*cyc_per_sam*sams);

cycles = 4;                     % 4 cycles of carrier wave
cyc_per_sam = cycles/N;

z = cos(2*pi*cyc_per_sam*sams + phi);               %carrier
x = cos(2*pi*cyc_per_sam*sams).*cos(phi);           %in-phase
y = cos(2*pi*cyc_per_sam*sams + pi/2).*sin(phi);    %quadrature

figure
plot(sams,sin(phi),'color','red', 'linewidth', 3)   %envelope
ylim([-1.2 1.2]);
box off
hold on

plot(sams,cos(phi),'color','blue', 'linewidth', 3)  %envelope
plot(sams,x,'color','blue')
plot(sams,y,'color','red')
plot(sams,z,'color','green', 'linewidth', 2)

set(gca, 'xaxislocation', 'origin')
set(gca, 'yaxislocation', 'origin')
set(gca, 'xgrid', 'on');
set(gca, 'ygrid', 'off');

set(gca, 'ytick', [0]);
cycles_per_tick = 0.25;
sam_per_tick = cycles_per_tick/cyc_per_sam;
set(gca, 'xtick', [0:16]*sam_per_tick);
set(gca,'XTickLabel',[' 0'; ' '; '2'; ' '; '4'; ' '; '6'; ' '; '8'; ' '; ' '; '11'; ' '; '13'; ' '; '15'; ' '])

green = [0 170 0]/256;
text(400, .9, '\uparrow sin(\phi(t))', 'color', 'red')
text(30, .86, '\uparrow cos(\phi(t))', 'color', 'blue')
text(147, .44, '\leftarrow I(t)', 'color', 'blue')
text(165, .30, 'Q(t) \rightarrow', 'color', 'red')
text(121, 1, '\leftarrow   cos(2\pift + \phi(t))   \rightarrow', 'color', green)
text(146, .87, '= I(t)+Q(t)', 'color', green)

title('In-phase and quadrature components (example)','fontsize', 12);
xlabel('\leftarrow  time (t)  \rightarrow','fontsize', 12)
ylabel('amplitude','fontsize', 10)

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27 October 2013

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Date/TimeThumbnailDimensionsUserComment
current15:31, 27 October 2013Thumbnail for version as of 15:31, 27 October 2013912 × 431 (29 KB)Bob KUser created page with UploadWizard

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