1.

Find the Nulls of the 8-element array in which elements are separated by λ/4 and phase difference is 0?(a) \(θ_n=cos^{-1}⁡(\left[±\frac{n}{2}\right])\)(b) \(θ_n=cos^{-1}⁡(\left[±\frac{n}{4}\right])\)(c) \(θ_n=sin^{-1}⁡(\left[±\frac{n}{2}\right])\)(d) \(θ_n=sin^{-1}⁡(\left[±\frac{n}{4}\right])\)I have been asked this question during an online interview.My question is taken from N-element Linear Array topic in chapter Antenna Array of Antennas

Answer»

The correct choice is (a) \(θ_n=cos^{-1}⁡(\left[±\frac{N}{2}\RIGHT])\)

The best explanation: The nulls of the N- element ARRAY is given by \(θ_n=cos^{-1}⁡(\frac{λ}{2πd} \left[-β±\frac{2πn}{N}\right])\)

⇨ \(θ_n=cos^{-1}⁡(\frac{λ}{2πλ/4}\left[0±\frac{2πn}{N}\right])\)

⇨ \(θ_n=cos^{-1}⁡(\left[±\frac{4n}{8}\right])\)

⇨ \(θ_n=cos^{-1}⁡(\left[±\frac{n}{2}\right]).\)



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