Question

What is the maximum power gain when the radiation resistance is 72Ω, loss resistance is 8Ω and the maximum directive gain is 1.5?

(a) 1.15

(b) 1.35

(c) 1.25

(d) 1.53

The question was posed to me in an internship interview.

This interesting question is from Power Gain topic in portion Antenna Parameters of Antennas

Answer 1

Right answer is (b) 1.35

For explanation: Maximum power gain Gpmax=ηr Gdmax

Radiation efficiency ηr=\(\frac{R_r}{R_r+R_l}=\frac{72}{72+8}=\frac{72}{80}=0.9\)

Now, Gpmax=ηr Gdmax=0.9×1.5=1.35