Question

Find the angle at which nulls occur for the two element array antenna with separation λ/4 and phase difference is π/2?

(a) 0

(b) π/2

(c) π/4

(d) π

I had been asked this question in quiz.

I want to ask this question from Factors topic in portion Antenna Array of Antennas

Answer 1

Correct option is (a) 0

For explanation: The normalized array factor is given by \(AF_n=\frac{AF}{2}=cos⁡(\frac{kdcosθ+β}{2})\)

⇨ AFn=0

⇨ \(cos(\frac{kdcosθ+β}{2})=0\)

⇨ ⁡\(\frac{(\frac{2π}{λ})(λ/4)cosθ+\frac{π}{2}}{2}=\frac{π}{2}\)

⇨ Cosθ=1

⇨ θ=0

So Nulls occur at 0°.