Question

What is the directive gain when the magnitude of radiation intensity equals to average radiation intensity?

(a) 4π

(b) ∞

(c) 1

(d) 0

I got this question in final exam.

My doubt stems from Directive Gain topic in portion Antenna Parameters of Antennas

Answer 1

Right option is (c) 1

Best explanation: Directive gain \(G_d = \frac{P_{d(\theta,\emptyset)}}{P_{avg}} = \frac{P_{d(\theta,\emptyset)}}{P_r/4\pi r^2} = \frac{P_{d(\theta,\emptyset)^{r^2}}}{P_r/4\pi} = \frac{U_{d(\theta,\emptyset)}}{U_{avg}} \)

 ∴ \(G_d = \frac{U_{(\theta,\emptyset)}}{U_{avg}}\)=1.