File:Aliasing-folding.svg

Summary

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 This work has been released into the public domain by its author, Nils R. Barth. This applies worldwide.
In some countries this may not be legally possible; if so:
Nils R. Barth grants anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.
Category:Self-published work#Aliasing-folding.svgCategory:PD-self#Aliasing-folding.svg
Category:Self-published work
SVG development
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 The SVG code is valid.
 This chart was created with Gnuplot.
Category:Valid SVG created with Gnuplot code:Charts#Aliasing-folding.svg
 This plot uses embedded text/digits.
Source code
InfoField
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)
Category:Aliasing Category:Folding Category:Digital signal processing Category:English-language SVG diagrams
Category:Aliasing Category:Digital signal processing Category:English-language SVG diagrams Category:Folding Category:PD-self Category:Self-published work Category:Valid SVG created with Gnuplot code:Charts