Simult. RH & LH Circ. Pol.

Hello,

If you combine a LH and RH circular polarized field with same amplitudes and arriving from same direction, the result will be a linear polarized field. A linear polarized field can be received by both a LH and RH circular polarized antenna, but with 3 dB loss with respect to the optimum case.

In my opinion, the word "simultaneous" has no meaning here, you can only switch between LH, RH or linear. It can only have some meaning in the receive case where you have amplifiers connected to both dipoles and do the phasing after the amplifiers. In this receive case you can have an antenna (with amplifiers) that has a LH and RH circular polarized output.

Best regards,

Wim PA3DJS

Might be worth a post on rec.radio.amateur.antenna Mike

"Simultaneous" sounds like a misnomer.. you can produce a given pattern at any given time, varying it by adjusting phase and drive, but you can't produce all "simultaneously".

Vertical and horizontal are orthogonal and form a basis set equivalent to RH and LH. A linear combination (phased, so it's an imaginary coefficient) allows you to produce one from the other. Also, from either given perspective, the other one seems to be recieving an equal mixture (e.g., a RH antenna is -3dB when recieving V or H).

Tim

-- Deep Friar: a very philosophical monk. Website:

You could do simultaneous RH & LH if they were on different frequencies, but not otherwise. There are two degrees of freedom in the polarization of a plane wave, so there are always two orthogonal polarizations--however you choose the basis set. Horizontal is orthogonal to vertical, RH is orthogonal to LH, and so on.

Linear and circular are special cases of elliptical polarization. Given a general elliptical polarization, you can construct the orthogonal one by keeping the same eccentricity, swapping the helicity (e.g. RH to LH), and making the major axes perpendicular.

Cheers

Phil Hobbs

I think some systems send two different signals simultaneously using rh and lh polarization.

John

In a crossed dipole system, you can produce either RHCP or LHCP signals depending on how the phasing harness is connected.

However, if you bring down both the horizontal as well as the vertical dipole signal on separate cables to the RF amplifier (and possible to the IQ down mixer), you can then create both sum and difference signals to get both RHCP as well as LHCP signals.

IQ and MIMO (Multiple Input, Multiple Output) might be usable keywords to limit the Google search.