What other excitation can you feed the horn antenna instead of using probe?

Hi everybody....

Does anybody know what other excitation to feed the horn antenna instead of using the coaxial probe. Thank you.

Regards,

a Gunn Diode in the waveguide feeding the horn,
a vivaldi antenna mounted in the horn

pretty much anything else is going to have some sort of probe it inject the RF into the waveguide

Dave
VK2TDN