Simult. RH & LH Circ. Pol.

[Tomas Ferrel]

"Antennas with orthogonal elements that are combined in phase
quadrature such as the crossed dipole with external 90 degree hybrid
coupler. This type of antenna can produce right-hand and left-hand
circular polarization simultaneously."

"Simultaneously"? Can anyone explain how this works? What is the
confguration of the coil and how is the signal applied to produce this
effect?

I don't understand how the "simultaneous" LH and RH fields would not
cancel each other out. Perhaps they mean the applied signal can cycle
intermittently between LH and RH.

Tomas Ferrel

 

[amdx]

"Antennas with orthogonal elements that are combined in phase
quadrature such as the crossed dipole with external 90 degree hybrid
coupler. This type of antenna can produce right-hand and left-hand
circular polarization simultaneously."

"Simultaneously"? Can anyone explain how this works? What is the
confguration of the coil and how is the signal applied to produce this
effect?

I don't understand how the "simultaneous" LH and RH fields would not
cancel each other out. Perhaps they mean the applied signal can cycle
intermittently between LH and RH.

Tomas Ferrel

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

 

[Tim Williams]

"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

 

[Paul Keinanen]

"Antennas with orthogonal elements that are combined in phase
quadrature such as the crossed dipole with external 90 degree hybrid
coupler. This type of antenna can produce right-hand and left-hand
circular polarization simultaneously."

"Simultaneously"? Can anyone explain how this works? What is the
confguration of the coil and how is the signal applied to produce this
effect?

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.