Antenna Reciprocity : Let's consider and discuss a bit

[radioCanada]

Hi all,

You might all have read the chapters on antenna
transmitting and receiving reciprocity, almost always
explained via an easy dipole or horn antenna.

Most of antennas are not that easy and especially
Antenna Arrays with complex feeding networks will
require - at my opinion - more considerations in order
to declare reciprocity.

For example:

If a feed network is corporate (parallel) and each branch
of the feeding network is completely asymetric, let s say composed
by dividers, the antenna will NOT receive the same amount of RX
energy, right ?

But at the same time, some of the energy will be back scattered
(due to no good S22 of the feed network) and appears back at
the antenna array elements.

NOW HERE is my problem to understand: Am I right that this energy
will at least change the near field solution of the antenna?
Or will it even have an influence on the radiation pattern in RX itself?

Think about other configurations: Leaky Wave Antennas, Traveling Wave
Antennas (Wire, Slot,..).

Give me some new ideas how to solve my problem and I am glad
to give you support , too!

RadioCC

 

[mac.feri]

Hi all,

You might all have read the chapters on antenna
transmitting and receiving reciprocity, almost always
explained via an easy dipole or horn antenna.

Most of antennas are not that easy and especially
Antenna Arrays with complex feeding networks will
require - at my opinion - more considerations in order
to declare reciprocity.

For example:

If a feed network is corporate (parallel) and each branch
of the feeding network is completely asymetric, let s say composed
by dividers, the antenna will NOT receive the same amount of RX
energy, right ?

But at the same time, some of the energy will be back scattered
(due to no good S22 of the feed network) and appears back at
the antenna array elements.

NOW HERE is my problem to understand: Am I right that this energy
will at least change the near field solution of the antenna?
Or will it even have an influence on the radiation pattern in RX itself?

Think about other configurations: Leaky Wave Antennas, Traveling Wave
Antennas (Wire, Slot,..).

Give me some new ideas how to solve my problem and I am glad
to give you support , too!

RadioCC

By definition all antennas on linear media are reciprocal. the mistake your are making is that you are considering the antenna and the divider as one block. the antenna it self has to be considered as an reciprocal element.

for your problem, first you have to simulate your antenna individually and then involve your microwave devices in the design to see if it does make any differences. if you apply a non reciprocal microwave device on your antenna input ( e.g a non reciprocal 3 or 4 port circulator) make sure you have terminated the other port properly. this way the wave reflected by the antenna will be delivered to the matched load on the other ports and will not result any problems for the antenna even in its near field.