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Antenna TheoryEC 544

Prof.Dr. Darwish Abdel Aziz

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LECTURE

Non-Uniform Arrays

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Binomial ArraysAmplitude Arrays

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 A. For No Side Lobes, Select

B. For No Grating Lobes, Select 

3.Spacing

2 . Array Factor 

d ≤ λ/2

d < λ 

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For N = 2(AF) 2 = cos u 

For N = 3

(AF) 3 = 1 + cos 2u= 2 cos 2 u 

For N = 4

(AF) 4 = cos u + cos 3u= 4 cos 3 u 

General Law of the Array Factor

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(AF) N

= 2 N-2 cos N-1 u 

Continue: The General Law

So the General law of the AF can be written as:

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It has been stated that binomial arrays do not exhibitany minor lobes provided the spacing between theelements is equal or less than one-half of a wavelength.

Unfortunately, closed form expressions for the directivityand half-power beamwidth for binomial arrays of anyspacing between the elements are not available.However , because the design using a λ / 2 spacing leadsto a pattern with no minor lobes, approximate closed-form expression for HPBW and maximum directivity for d

= λ / 2 spacing only have been derived by L. J. Ricardi,and they are given, respectively, by

Directivity and HPBW

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Continue : Directivity and HPBW