Question

If the current input to the antenna is 100mA, then find the average power radiated from the half-wave dipole antenna?

(a) 365mW

(b) 0.356mW

(c) 0.365mW

(d) 356mW

I had been asked this question during an interview.

Origin of the question is Power Radiation from Half Wave Dipole topic in portion Antenna Parameters – II of Antennas

Answer 1

Correct choice is (a) 365mW

Best explanation: Average Power radiated from the half-wave dipole Pavg=\(I_{rms}^2 R=(\frac{I_m}{\sqrt 2})^2 R \)

Radiation resistance of a half-wave dipole is 73Ω.

Given Im=100mA  =>  Pavg=\((\frac{100×10^{-3}}{\sqrt 2})^2×73=365mW.\)