# Why a RHC antenna in Tx mode become LHC in receiving mode?

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1. Jan 21, 2013

### yungman

How do you characterize an antenna in receiving mode? The book said a LHC antenna in transmitting mode is RHC in receiving mode. Also if the antenna is LHC in transmitting mode, it's transmission characteristic is defined as $\hat {E}_{(z,t)}=\frac{\hat {x}+\hat {y} j}{\sqrt{2}}$. But the same antenna is RHC in receiving mode and it's receiving characteristic is defined as $\hat {E}_{(z,t)}=\frac{\hat {x}-\hat {y} j}{\sqrt{2}}$?

Is it because the same antenna when characterized as LHC when transmitting in +z direction, when placed on the z axis as the receiving antenna, has to be characterized in -z direction and therefore is RHC antenna in receiving mode?

2. Jan 21, 2013

### skeptic2

I understand you to be talking about circularly polarized antennas. If for instance you have two fixed sites talking to each other. The transmitting antenna is right hand circular (RHC) going out, then the incoming signal will see the antenna from the opposite direction so it will see a left hand circular antenna.

Incidently, the polarization of a circularly polarized signal will reverse with each reflection, so if both the Tx and Rx antennas are properly polarized, this arrangement will reduce multipath and presumably Fresnel Zone effects.

Last edited: Jan 21, 2013
3. Jan 21, 2013

### yungman

Thanks. So a RHC antenna in transmitting mode become a LHC antenna in receiving mode.

Yes, I draw out the polarized wave travels from an RHC antenna and looks like LHC for the receiving as the propagation is in opposite direction for the two antennas.

This RHC and LHC is very confusing because of how IEEE defined and different books have different ways of defining Right or Left hand notation. A RHC for Kraus is LHC for Balanis....Which both are about the most popular book in antennas!!!! They are pretty much the standard of antenna books and they defined this totally opposite.

Thanks