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A 4-isotropic element broadside array separated by a λ/2 distance has nulls occurring at ____________(a) \(cos^{-1} (±\frac{n}{2}) \)(b) \(cos^{-1} (±\frac{4n}{2}) \)(c) \(sin^{-1} (±\frac{n}{2}) \)(d) \(sin^{-1} (±\frac{n}{4}) \)I got this question in semester exam.This intriguing question comes from Radiation Pattern for 4-Isotropic Elements in portion Antenna Array of Antennas |
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Answer» RIGHT option is (a) \(cos^{-1} (±\frac{N}{2}) \) The best I can explain: The nulls of the N- element ARRAY is given by \(θ_n=cos^{-1}(\frac{λ}{2πd} \left[-β±\frac{2πn}{N}\right])=cos^{-1}(\frac{λ}{2πd} \left[±\frac{2πn}{N}\right])\) ⇨ \(θ_n=cos^{-1}(\frac{λ}{2π(λ/2)}\left[±\frac{2πn}{N}\right])=cos^{-1} (±\frac{2n}{4})=cos^{-1} (±\frac{n}{2}) \) |
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