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