Question

The value at which the second null occurs in H-plane of rectangular aperture of a*b is given by ____

(a) sin^-1⁡(2λ/a)

(b) sin^-1⁡(λ/a)

(c) sin^-1⁡(a/2λ)

(d) sin^-1⁡(a/λ)

This question was posed to me during a job interview.

I would like to ask this question from Aperture Antenna in portion Aperture Antenna of Antennas

Answer 1

Correct option is (a) sin^-1⁡(2λ/a)

Explanation: The area the power is radiated is given by Beam-width. The beam-width between the first nulls is the FNBW. For H-plane \(\frac{ka}{2}\) sinθ=nπ

⇨ θ= sin^-1⁡(nλ/a)

⇨ For null n=2     θ= sin^-1⁡(2λ/a).