Why do I get back radiation when simulating this horn antenna?

Hi all,

I have design a horn antenna with a coupled metallic lens and the radiation pattern shows a bad Front/Back ratio that is confirmed in the animated fields visualization. Some ideas of why is this happening? Could be the lens attached to the mouth of the horn that is modifying the pattern somehow in the 180o direction? Please I need an explanation because this is really odd to me... By the way, Im using CST MWS 2014.

Thanks!

Hi dovod,

While I don't have any details on your antenna setup, it seems like the lens should be the issue.

Have you confirmed the lens' properties independently? It may have a fair amount of scattering.

Have you studied the currents on the outside surface of your horn antenna, particularly around the mouth of the horn? It sounds like you might have high currents that are leaking back onto the outer surface of your antenna, and these currents might be creating the radiation. I think there is a Field Monitor in CST that you can choose that will capture visualization of the currents on the outside of your antenna. If this is the case, you may need to look for ways to suppress that current.