[stephen_g]

GaN doesn’t really change the link budget (it does have different compression characteristics than GaAs, but you just back off a little), the OP said as the size of the terminal gets smaller, so I assume they’re talking about the aperture size. You can compensate somewhat for the lost antenna gain with a higher power PA but depending on the antenna pattern, you might hit the ESD (energy spectral density) limit earlier.

[aDfbrtVt]

I see, the reduction of antenna gain with terminal miniaturization makes sense. I didn't know if the noise figure of a GaN amplifier was worse.

Why would a change in the antenna radiation pattern limit the power spectral density, is it a regulatory limit?

[walrus01]

Smaller diameter parabolic antennas have wider center beam peak gain area in focal axis, and less precise dead on aiming at a specific satellite. Something like a 90cm flyaway is worse than a 120cm flyaway.

In general the radiation pattern envelope (RPE) gets worse when viewed on an azimuth and elevation plot chart as the circular parabolic (or elliptical offset parabola) gets smaller.

Same general idea of why you might be able to successfully coordinate a fcc part 101 fdd band plan link terrestrially in a major urban area with a 120cm antenna with tighter RPE than same theoretical link if you submit it with cheaper antennas.