polarization in nature, technology and radio
DESCRIPTION
David Conn VE3KL. Polarization in Nature, Technology and Radio. 1932 Chevy ?. Credits. http://www.polarization.com/land/land.html. http://www.windows.ucar.edu/tour/link=/earth/images/earth_magneto_image.html&edu=high. Acknowledgements. Wild Rose Chapter 151 QCWA - PowerPoint PPT PresentationTRANSCRIPT
04/19/23 David Conn VE3KL QCWA Sept 2006
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Polarization in Nature, Technology and Radio
David Conn VE3KL
Credits
http://www.windows.ucar.edu/tour/link=/earth/images/earth_magneto_image.html&edu=high
http://www.polarization.com/land/land.html
1932 Chevy ?
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Acknowledgements
Wild Rose Chapter 151 QCWA
QCWA Chapter 70 Members Ken Oelke VE6AFO Graham Ide VE3BYT Clare Fowler VE3NPC Ken Pulfer VE3PU Doug Leach VE3XK
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What is Polarization ?
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Light and Radio Waves
• Composed of Electric Fields, E
• E at right angles to direction of propagation
• E can be Horizontal, Vertical, Circular..
• Unpolarized…….. The Sun
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Why is Polarization Important ?
• The Ionosphere and materials change the polarization of Radio Waves
• Operation of Lasers, LCD displays, Sun Glasses
• Medical research…. Diabetes
• Biology .. Insects..
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The Basics … #1[Reflection..Refraction]
Air
Incoming Plane Wave
Reflected Wave
Refracted Wave
Standing Wave RegionSWR
Water
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The Brewster Angle [E in plane of the Screen]
Air
Water
Incoming Plane Wave of LightRefracted Wave
NO ReflectionLike a matched LoadSWR = 1:1
53 Degrees
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Horizontal Wires
Vertically Polarized
Horizontally Polarized
Basics.. #2 The Wire GridPolarizer
Incoming Unpolarized Light/Radio Wave
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Horizontal Wires
Vertically Polarized Wave
The Wire GridReflector or Transmitter
Circularly Polarized Wave
Horizontally Polarized
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• Rainbows
• Sun Glasses
• Liquid Crystal Displays
• The Magnetosphere
• Four Antennas
• Insects
Examples
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RainbowsAre they Polarized ?
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YES…But Why?
Note the Double Rainbow
HorizontalAt Top
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Here is Why
42 degrees
Polarized perpendicular to the ScreenHorizontal
Unpolarized Light from the Sun
Brewster Angle
Water Droplet
Vertical
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Polarized SunglassesTransmit Vertically Polarized Light
Vertical lost due to BrewsterHorizontal lost by Glasses
Horizontally Polarized
Brewster Angle
Angle Important
Wire Grid
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Liquid Crystals
http://nobelprize.org/educational_games/physics/liquid_crystals/history/
Liquid Crystal
cyanobiphenyl materials
http://www.kth.se/fakulteter/TFY/kmf/lcd/lcd~1.htmCredits
1888
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LCD Display http://nobelprize.org/educational_games/physics/liquid_crystals/history/
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Polarization in the IonosphereBig Impact on Radio and EME
Linear Polarization(45 degrees tilt) Elliptical Polarization
Earth’s Magnetic Field
Electrons in the Ionosphere 70 Km
50 MHz
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Polarization in the IonosphereFaraday Rotation
HorizontalPolarizationInput Vertical Polarization
Output
Earth’s Magnetic Field
Electrons in the Ionosphere
A Horizontal Dipole will NOTTalk to a Horizontal Dipole.
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Some Examples of Circularly Polarized Antennas
• Two Crossed Dipoles …… Basic
• Two Crossed Dipoles …… Very simple
• The Classic Helix …. Complex
• The Skew Planar …. Very Complex
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Two Crossed Dipoles
Direction of Propagation
Horizontal Antenna
Vertical Antenna
50 Watts
50 Watts
λ/4
Transmitter100 Watts
Antennas Fed In-Phase(Details not shown)
LHC
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A Simple Circularly Polarized Antenna
Two crossed dipolesConnected in parallelOne LONGER than the other
Radiates into the ScreenZin = 50 Ohms
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• Invented by John Kraus
• Used by Amateurs for Satellite Communications
• Difficult to Analyze
• Relatively High Gain …. 15 dBc
The Helix Antenna
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The Helix Antenna
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• A Story of its Own
• Researched extensively by Graham Ide (VE3BYT)
• Omni Directional and Circularly Polarized
• First reported in QST 1960’s
• Not used again until Graham got interested
The Skew Planar Antenna900 MHz Beacon Applications
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The Skew Planar Antenna
70 Cm Beacon ApplicationsVE3BYT
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InsectsSome Insects have complex polarized eyes
http://xray.optics.rochester.edu/workgroups/cml/opt307/spr04/greg/
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• The Concepts and Use of Polarized Signals Span many disciplines
• Two Ideas Presented:
The Brewster Angle
The Wire Grid
Summary
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VY 73 David
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Where to Get More Informationand Credits
http://webphysics.davidson.edu/physlet_resources/dav_optics/Examples/polarization.html
http://en.wikipedia.org/wiki/Liquid_crystal_display
http://www.ngsir.netfirms.com/englishhtm/Lissajous.htm
Fields and Waves in Communication Electronics: Ramo, Whinnery, Van Duzer ; John Wiley, third edition, 1994, ISBN 0-0471-58551-3