Circular polarization: Difference between revisions

Revision as of 17:08, 15 May 2006

Revision as of 17:08, 15 May 2006

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Circular polarization may be referred to as ''right'' or ''left'', depending on the direction in which the electric field vector rotates. Unfortunately, two opposing, historical conventions exist. In [[physics]] and [[astronomy]], polarization is defined as seen from the <i>receiver</i>, such as a [[telescope]] or [[radio telescope]]. By this definition, if you could stop time and look at the electric field along the beam, it would trace a helix which is the same shape as the same-handed screw. For example, right circular polarization produces a right threaded (or forward threaded) [[screw]]. In the U.S., [[Federal Standard 1037C]] also defines the handedness of circular polarization in this manner. In [[electrical engineering]], however, it is more common to define polarization as seen from the <i>source</i>, such as from a transmitting antenna. To avoid confusion, it is good practice to specify "as seen from the receiver" (or transmitter) when polarization matters.

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== FM radio ==

The term "circular polarization" is often used erroneously to describe mixed polarity signals used mostly in [[FM radio]] (87.5 to 108.0 MHz), where a vertical and a horizontal component are propagated simultaneously by a single or a combined array.

This has the effect of producing greater penetration into buildings and difficult reception areas than a signal with just one plane of polarization.