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Left hand and right hand circular polarization

by amir11950
Tags: circular, hand, polarization
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Aug25-11, 01:27 PM
P: 1
Hello everyone. I want to purchase an RFID reader and they asked me if I wanted a left hand or right hand circular polarized reader. I have no clue what this means. Could anyone please help me understand this? I saw some website and all I understood was that the signal travels either clockwise or counter-clockwise. He told me left hand circular polarized was selling and the right hand wasn't selling at all. Any theories as to why this is?
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Claude Bile
Aug26-11, 08:56 AM
Sci Advisor
P: 1,477
The "handedness" of circular polarisation describes the direction of rotation of the E field vector as it propagates.

There is a degree of ambiguity here; what you call RHCP depends on whether you are looking behind or toward the incoming wave. The convention is not consistent in my experience, some fields describe the handedness looking into the oncoming wave and some do the opposite.

As for why LHCP sells better than RHCP, I have no clue. Fundamentally, they ought to be quite symmetric.

Aug26-11, 10:03 AM
P: 617
Theoretically, left-handed circularly polarized light and right-handed circularly polarized light are symmetrical and there is nothing different between them beyond a flip in helicity. I think your case is more dependent on sociology than on physics. RFID tags with left-handed antennas will couple better with the left-handed reader, and tags with right-handed antennas will couple with the right-handed readers better. So if left-handed readers are selling better, I would presume it is because left-handed tags are used more often by manufacturers.

What you need to do is decide what kind of tags you intend to use the reader on and do some research on those tags to see what type of reader they interact best with.

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