Question

The necessary condition for the direction of maximum side lobe level of the N-element isotropic array is _______

(a) \(ᴪ=±\frac{2s+1}{N} π \)

(b) \(ᴪ=±\frac{2s+2}{N} π\)

(c) \(ᴪ=±\frac{2s}{N} π\)

(d) \(ᴪ=±\frac{2(s+1)}{N} π\)

This question was addressed to me in an interview.

My question is from Array of N-Isotropic Sources topic in chapter Antenna Array of Antennas

Answer 1

Right choice is (a) \(ᴪ=±\frac{2s+1}{N} π \)

The explanation: The secondary maxima occur when the numerator of the array factor equals to 1.

⇨ \(sin(\frac{Nᴪ}{2})=±1\)

⇨ \(\frac{Nᴪ}{2}=±\frac{2s+1}{2} π \)

⇨ \(ᴪ=±\frac{2s+1}{N} π .\)