H Plane horn antenna with SIW

Hi guys,

I am working on a h plane horn antenna.
First I calculate all dimensions that it needs, then I simulate it in the CST but my results are strange.
I have a good gain about 6 dB that it is fine in this level
I do not have any loss when I am checking the E-Fields
But my s11 is awful, it is almost zero, working like a resonator.
Do you have any idea why it is like that ?
I am suspicious to feeding and boundaries, because usually these two make your s11 so bad, I used a wave guide port for feeding and I choose open add space as boundaries.
Does anybody have any idea?
I attached the picture of my antenna.

Thanks

I would try to put blocking vias or wall on radiating edge and compare results. Also I would try to make SIW waveguide filter with microstrip feeding transition, after ensuring it works and have good S11 S21 I would cut one microstrip port and edit it with adding vias or walls to produce horn.

Thanks for your reply
I actually tried it already. I designed a horn antenna by PEC walls not SIW structure( like usual h plane horn antenna) with same dimensions. But my results were exactly same.
I really do not have any idea what is the problem.
Shall I just connect waveguide port to the substrate in wave guide or it should be connected to the metals too ?
what about the boundries? I used open add space, is the distance important ?
I appreciate it if you have any other ideas share it with me.

Thanks



I just change the boundaries from open add space to electric (Et=0) and just left the z direction for raddiation as an open add space and my results S11 is all under -10dB
but it does not make sense and this way is not right

Thanks for your reply

I designed my horn just with metal walls like a usual horn (without any SIW), but the result was same.not good at all.
then I changed the boundaries to electric(Et=0) in all directions and left the z direction as open add space, and the result was perfect all better than -10dB , but this way is not right, I should get the same results in open add space boundaries.
do you have any idea about it ?

I actually solved the problem with S11. But, Unfortunately I have another problem.
I optimized the waveguide size and then I got good result in s11. But this changes make my E-Fields zero. when I am checking the e-fields in CST it is all zero !
Do you have any idea about that?

Thanks

I think it is all related to excitation modes or simulation problems. I am not expert in both areas.
Mostly i saw papers on slot antennas using SIW. But interested in H Plane horn using SIW very much and will be happy to see if you got any good results.