lecture 4.pptx
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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