Surface mounted HORN?

I am simulating the following figure but don't know how to surface mount the horn antenna in CST?

Any ideas of how to do it....The prototype is shown below.

Awaiting replies,
Regards

in my experience, you can have a patch antenna excite a standard waveguide horn. It works ok. It is especially useful if you need isolation between multiple antennas, as in a cw radar with a transmit and two receive horns. If you just had 3 patches on the same board, the leakage between the patches would be too high.

But the reality is that to get good high gain, you need a very long horn with wide aperture...not that conducive to mounting on a pcb. I have had good luck laying a dielectric lens on top of a patch antenna to get better gain. You might want to go in that direction.

Thankyou for the suggestion. I'll keep this option open as well...

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How to do these steps as well in CST?