(Q). Paraboloidal reflector has a diameter D=20m and is designed to operate at f=6 GHz with an illumination efficiency η= 0.54. What is the antenna gain in decibels?

The effective area = πd^2*η

= π*10^2*0.54

= 54

and Wavelength,

λ = 3*10^8/(6*10^4)

= 0.05 m

Now, the gain of the reflector antenna is given by

G = 4*π*A/ λ ^2

=852733.821

In decibels

G_dB = 10log(G) = 59.308 dB