File:Aliasing-folding.svg

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Description
English: Graph of frequency aliasing, showing folding frequency and periodicity. Frequencies above ƒs/2 (the Nyquist frequency) have an alias below ƒs/2, whose value is given by this graph. See Spectral imaging of the atmosphere, by G. G. Shepherd, Figure 2.9(a), p. 43 for similar diagram.
Date
Source Own work
Author Nils R. Barth
Permission
(Reusing this file)
Nils R. Barth, the copyright holder of this work, hereby publishes it under the following license:
Public domain I, the copyright holder of this work, release this work into the public domain. This applies worldwide.
In some countries this may not be legally possible; if so:
I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.
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Source code
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Gnuplot code
Source code
# Graph of aliasing frequencies
# Triangle wave

# Set terminal
set terminal svg enhanced size 300 200 fs 10
set samples 1001  # high quality
set border 31 linewidth .3 # thin border

set output "aliasing-folding.svg"

# Ranges
set xrange [-.2:2.2] # 2 cycles, with room for labels
set xtics  ( \
     "0"     0,                                        \
   "fs/4"  .25,   "fs/2"  .5,  "3fs/4"  .75,   "fs" 1, \
  "5fs/4" 1.25,  "3fs/2" 1.5,  "7fs/4" 1.75,  "2fs" 2  \
           ) # Key feature (fold) is at .5; add .25 for reference
set yrange [-.1:1.1] # Slight headroom from max of 1
set ytics ( \
   "0"  0,  "fs/4"  .5,  "fs/2" 1  \
          ) # Corresponding y values

# Zero axes and grid as guidelines, no key (self-explanatory)
set zeroaxis
set grid
unset key

###########################
# Define and plot function
###########################

tri(x) = acos(cos(2*pi*x))/pi # normalized triangle wave

plot tri(x)

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23 April 2009

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9d3d2d940c0a47c73a28d17942649d4342af3248

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Date/TimeThumbnailDimensionsUserComment
current13:49, 9 February 2019Thumbnail for version as of 13:49, 9 February 2019300 × 200 (16 KB)Bob KReverted to version as of 18:57, 23 April 2009 (UTC)
13:13, 9 February 2019Thumbnail for version as of 13:13, 9 February 2019697 × 324 (50 KB)Bob KProvide a .svg version of Aliasing-folding.png
18:57, 23 April 2009Thumbnail for version as of 18:57, 23 April 2009300 × 200 (16 KB)NbarthMuch cleaner in Inkscape
15:26, 21 April 2009Thumbnail for version as of 15:26, 21 April 2009300 × 200 (15 KB)Nbarth{{Information |Description={{en|1=Graph of frequency aliasing, showing folding frequency.}} |Source=Own work by uploader |Author=Nbarth |Date=2009-04-21 |Permission= |other_versions= }} <!--{{Ima

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