Question

What is the directivity of antenna having effective aperture 1 m^2?

(a) \(\frac{4\pi}{\lambda^2}\)

(b) \(\frac{\lambda^2}{4\pi}\)

(c) 1

(d) 4π

I had been asked this question in an international level competition.

My question comes from Directivity in portion Antenna Parameters of Antennas

Answer 1

Correct option is (a) \(\frac{4\pi}{\lambda^2}\)

To elaborate: Directivity D=\(\frac{4\pi}{\lambda^2}A_e\)

Given effective aperture Ae=1m^2

⇨ D=\(\frac{4\pi}{\lambda^2}A_e = \frac{4\pi}{\lambda^2}  × 1 =\frac{4\pi}{\lambda^2}\)