[opendtv] Re: Circular, elliptical antenna polarization improves mobile DTV reception reliability
- From: "John Shutt" <shuttj@xxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 27 Apr 2011 22:50:27 -0400
"True" CP with a true CP receive antenna has an advantage over a horizontally
polarized signal when in high multipath environments. When a CW CP signal
bounces off of a hard reflector (such as a building) it becomes CCW polarized,
and is rejected by the CW polarized receive antenna. The direct path maintains
its CW polarization and is accepted by the CW polarized receive antenna.
The advantage of CP, dual polarization, elliptical polarization, or however you
wish to categorize it, in a mobile environment is simply that the receive
antenna is rarely horizontally oriented. Therefore, if there is a vertical
component to the broadcast signal, there is more signal for a vertically
oriented antenna to receive.
John
----- Original Message -----
From: Mark Aitken
To: opendtv@xxxxxxxxxxxxx
Sent: Wednesday, April 27, 2011 8:47 PM
Subject: [opendtv] Re: Circular, elliptical antenna polarization improves
mobile DTV reception reliability
Dale, correct to both of your points. As to "advantage" of CW or CCW true
circular...only needed to provide isolation or discrimination from opposing
rotational emissions...used in space activities for example for DTTH satellite.
Regards,
Mark
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