Originally Posted by 300ohm
Plus it would require a separate antenna for each channel on the same frequency.
For an OAM Multi-Antenna Receive Array, I'm not sure that would be true.
If the modes are truly "orthogonal", as is claimed, then the Receiver IF
outputs could be processed digitally with the requisite phase shifts and
amplitude weightings to form each of the say l=4 configurations. This
process would need to be done in PARALLEL, using the SAME IF digital
samples (hey, that's what super-fast signal processors are for). And by
reciprocity, the same process could be performed in REVERSE for an
OAM Transmit Array. [I'll keep reading to see if this a viable alternative....]
However, since the Helicoidal Parabola used a PHYSICAL structure to generate
the increasing phase offsets around the circumference, there would need
to be separate Transmit antennas for each of the eigenvalues, and DOUBLE
that if H/V or RHCP/LHCP Polarization for an additional DOUBLING of capacity.
BTW: If used for Broadcast coverage, a set of (say) EIGHT OAM Transmit
Antenna Arrays (probably not FOUR, depending on beamwidth) would need
to encircle the Broadcast tower, resulting in EIGHT sweet-spots and EIGHT
self-interference zones as the LEFT side of the pattern overlaps the RIGHT
side of the adjacent pattern.
Suppose antenna eigenvalue patterns ALTERNATE, so l = positive integers
alternate with l = negative integers for the same eigenvalues. In the case of
Helicoidal Parabolic Antennas, the phase step at the Gap would alternate
between positive and negative X-Axis offsets, so that in the self-interference
regions, the receive array would see an increasing (or decreasing) phase
shift from BOTH antennas.
If [and that's a very BIG IF] it is possible to construct the arrays so that
these L/R patterns result in the SAME E&M Field orientations in the
self-interference zones, i.e. are mirror images of each other, then the
self-interference MIGHT not be all that bad [Thesis project anyone????].....