How to increase bandwidth of horn antenna

[love_kl]

hi everyone!!!
I've been designing horn antenna for Ku band with realized gain >15db
But I can't rules out of learning the way to optimize bandwidth, S11 always about -3-->-7dB
thanx
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[Kohi_boy]

I noticed you used lump ports.

But in actual implementation, how are you going to excite the horn?

 

[love_kl]

I intend to excite by a short dipole, I tried to use waveport but I ruled out as soon as solve.