Horn antenna Radiation

Hi all.
a basic quastion:
if i have a horn antenna with the Gain 10 dB, the 3 dB beamwidth is 51 degree. i want to radiate for example a teflon plate. What is the area radiated by the horn antenna if i am in Far field?


Thank you all.

Use pure geometry, please . The Far Field zone depends on your aperture size vers, wavelength

Hi. It is a horn antenna 100x130 (mm). the Frequency Range is 3GHz.

thanks

Okay, now calculate the far zone using lambda and aperture size, then use geometry to find the spot size at a chosen distance.