Hi, Gurus,
I have a horn antenna as the attachment.
Now I want to calculate the distance between the horn antenna and the object.
I wonder where is the ref plane of the horn antenna? Someone said it should be at the 1/3 position, is that right?
Best,
Tony Liu
not entirely sure what you mean by "reference plane".
in a lot of cases where i am referencing to a pyramidal horn antenna, the open end of the table makes a good mathematical "reference plane", i.e. some place where you can arbitrarily set the phase as being "zero" degrees,
There is no meaning on measuring something inside the antenna, so If the lenght of the horn is much bigger than the apperture height, you could consider the horn output window as the plane at which radiation pattern will be plotted.
Seen from fare field is phasecenter an electric reference point for each frequency.
That is what I use as reference distance and for assuming received relative phase position.
Phasercenter Is a defined function in CST.
Phase center description: https://en.wikipedia.org/wiki/Phase_center
Horn antenna phase center calculation: https://ieeexplore.ieee.org/document/1139799
Especially for wideband horn antenna do it probably not exist a fixed " electric plane" of any practical use even if it maybe can somehow be defined.
There are three posibilities to measure the gain of the horn antennas: using the distance from the aperture (margin of the horn antenna), using the phase center of the horn antenna, or to use the distance from the excitation port.
Is only a small gain difference between them if the distance between antennas is very high in far field (>32*[(D^2)/λ].
The phase center distance of the horn depends by frequency, but gives the highest antenna gain.