A 28 GHz radio link uses a tower-mounted reflector antenna with a gain of 32 dB and a transmitter power of 5 W.
(a) Find the minimum distance within the main beam of the antenna for which the U.S-recommended safe power density limit of 10 mW/cm2 is not exceeded.
(b) How does this distance change for a position within the sidelobe region of the antenna if we assume a worst-case sidelobe level of 10 dB below the main beam?
(c) Are these distances in the far-field region of the antenna? (Assume a circular reflector, with an aperture efficiency of 60%.)