1.

The direction of first null of the broadside array of N-Isotropic sources is _____(a) \(cos^{-1}([±\frac{λ}{Nd}])\)(b) \(cos^{-1}⁡([±\frac{πλ}{Nd}])\)(c) \(cos^{-1}⁡([±\frac{2πλ}{Nd}])\)(d) \(cos^{-1}⁡([±\frac{λ}{2Nd}])\)I have been asked this question at a job interview.Enquiry is from Array of N-Isotropic Sources topic in chapter Antenna Array of Antennas

Answer»

The CORRECT answer is (a) \(COS^{-1}([±\frac{λ}{Nd}])\)

Explanation: The NULLS of the N- element array is given by \(θ_n=cos^{-1}⁡(\frac{λ}{2πd} [-β±\frac{2πn}{N}])\)

Given it’s a broadside array so β=0 and n=1 for FIRST NULL

\(θ_n=cos^{-1}⁡(\frac{λ}{2πd} [±\frac{2πn}{N}])= cos^{-1}⁡([±\frac{nλ}{Nd}])=cos^{-1}⁡([±\frac{λ}{Nd}])\)



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