File:Pulse density modulation.svg
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Size of this PNG preview of this SVG file: 720 × 540 pixels. Other resolutions: 320 × 240 pixels | 640 × 480 pixels | 1,024 × 768 pixels | 1,280 × 960 pixels | 2,560 × 1,920 pixels.
Original file (SVG file, nominally 720 × 540 pixels, file size: 69 KB)
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Structured data
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Summary[edit]
DescriptionPulse density modulation.svg |
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[edit]
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[edit]
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.http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue |
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: Moxfyre at English Wikipedia
- 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.
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Original upload log[edit]
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 | 720 × 540 (69 KB) | Wdwd (talk | contribs) | Change text from "PCM signal" to "analog signal" | |
20:21, 2 February 2012 | 720 × 540 (69 KB) | Wdwd (talk | contribs) | Change text from "PCM signal" to "analog signal" | ||
06:07, 22 April 2009 | 720 × 540 (41 KB) | Moxfyre (talk | contribs) | Previous version cut off y-axis captions, whoops! | ||
18:53, 21 April 2009 | 720 × 540 (19 KB) | Moxfyre (talk | contribs) | made it coarser and square-waved, so the PDM is easier to visualize | ||
01:38, 17 December 2007 | 607 × 494 (32 KB) | Moxfyre (talk | contribs) | {{Information |Description={{en|Self-made using en:Python (programming language), en:NumPy and en:Matplotlib. Here's my implementation of the algorithm derived in en:pulse-density modulation: <source lang="python"> from pylab import |
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