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Old Dec 24, 2010, 05:33 AM
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Notice the important remark from lonestar : if your tranmitter antenna is linearly polarized and your receiver antenna is circularly polarized, which is the case discussed here, then you always loose 3dB.

The best case would be to have a circular polarized antenna at the transmitter and at the receiver (it is the case for GPS for example).

more details here :

http://www.antenna-theory.com/basics/antennapol.php

"Suppose now that a linearly polarized antenna is trying to receive a circularly polarized wave. Equivalently, suppose a circularly polarized antenna is trying to receive a linearly polarized wave. What is the resulting Polarization Loss Factor?

Recall that circular polarization is really two orthongal linear polarized waves 90 degrees out of phase. Hence, a linearly polarized (LP) antenna will simply pick up the in-phase component of the circularly polarized (CP) wave. As a result, the LP antenna will have a polarization mismatch loss of 0.5 (-3dB), no matter what the angle the LP antenna is rotated to."
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