File:Pulse density modulation.svg
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Original file (SVG file, nominally 720 × 540 pixels, file size: 69 KB)
Summary
| Description |
English: Self-made graph of a w:en:sine wave in w:pulse-code modulation and w:pulse-density modulation. |
| Date | 23 October 2007 (original upload date) |
| Source |
Transferred from en.wikipedia to Commons. Transfer was stated to be made by User:moxfyre. This W3C-unspecified plot was created with Matplotlib. |
| Author | Moxfyre at English Wikipedia |
Program code
Here is the Python code to produce this graph, using NumPy and Matplotlib. Includes my implementation of the algorithm derived in pulse-density modulation:
#!/usr/bin/python2.5
from pylab import *
from numpy import *
def pdm(x):
y = zeros_like(x)
qe = zeros_like(x)
qe[-1] = 0 # inital [[:en:quantization error]] is 0
for n in range(x.size):
y[n] = 2*( x[n] > qe[n-1] ) - 1
qe[n] = y[n] - x[n] + qe[n-1]
return y, qe
def squarify(x, y):
halfway = ( x[1:]+x[:-1] )/2
xo = hstack(( x[0], repeat(halfway, 2), x[-1] ))
yo = repeat(y, 2)
return xo, yo
t = arange(100.0)
x = sin(2*pi/100 * t)
y, qe = pdm(x)
to, yo = squarify(t, y)
plot( label="PDM sine wave", *squarify(t,y) )
plot( t, x, label="PCM sine wave", linewidth=5 )
axis((-5, 105, -1.25, 1.5))
legend(loc='upper right')
xticks(fontsize=16)
yticks(fontsize=16)
xlabel("Discrete time (n)", fontsize=18)
ylabel("Signal amplitude",fontsize=18)
savefig("pdm.svg", transparent=True)
Licensing
Moxfyre at English Wikipedia, the copyright holder of this work, hereby publishes it under the following licenses:
|
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License. |
This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported, 2.5 Generic, 2.0 Generic and 1.0 Generic license.
Attribution:
- You are free:
- to share – to copy, distribute and transmit the work
- to remix – to adapt the work
- Under the following conditions:
- attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
- share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.
You may select the license of your choice.
Original upload log
The original description page was here. All following user names refer to en.wikipedia.
- 2007-10-23 06:56 Moxfyre 607×494×0 (33019 bytes) Self-made using algorithm derived in [[pulse-density modulation]]
File history
Click on a date/time to view the file as it appeared at that time.
| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 20:22, 2 February 2012 | No thumbnail | 720 × 540 (69 KB) | wikimediacommons>Wdwd | Change text from "PCM signal" to "analog signal" |
File usage
The following page uses this file:
