Question

The directivity of a prime-focal parabolic reflector antenna is 30 dBi. If the efficiency of the antenna is 50%, the gain of the antenna is:
1. 27 dBi
2. 33 dBi
3. 25 dBi
4. 80 dBi

Answer 1

Correct Answer - Option 1 : 27 dBi

Given:

Directivity (D) = 30 dBi, η = 50% = 0.5

In dB (η) = 10 log (0.5) = -3 dB

We know that,

\(\eta = \frac{G}{D}\) 

In dB: (η)_dB = (G)_dB – (D)_dB

(G)_dB = (η)_dB + (D)_dB

= -3 dB + 30 dB

= 27 dB