Array Antennas

Array Antennas

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  Arrays: Linear, Planar, andCircular By: John Kevin A. Toral
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  Course Outline I) Introduction A)Elements of Antenna B) Gain or directivity of Antenna II) Types of Array A) Linear 1) 2-Element Array 2) N-element Linear Array with Uniform Amplitude and Spacing B) Circular C) Planar
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  Introduction  Antenna composesof elements  These elements has low values of directivity  In application, antennas are required to have very high gains.
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  How to achievegreater gains  Increase the electrical size of the antenna  Enlarging the dimensions of single elements  The most efficient is to use an array.
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  What is anarray?  An antenna array is a set of 2 or more antennas. The signals from the antennas are combined or processed in order to achieve improved performance over that of a single antenna. -antenna theory
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  Tasks of AntennaArray  Increase the overall gain  Provide diversity reception  Cancel out interference from a particular set of direction  Determine the direction of arrival of the incoming signals  To maximize the Signal to Interference Plus Noise Ratio(SINR)
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  Types of Array
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  Linear Arrays  Antennaelements arranged along a straight line.  Elements of the array are uniformly-spaced.
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  Classifications of LinearArray  2-Element Array  N-element Linear Array with Uniform Amplitude and Spacing
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  2-Element Array
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   The arrayelements are identical  They are oriented in the same way is space (identical polarization)  Their excitation is of the same amplitude
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  N-element Linear Arraywith Uniform Amplitude and Spacing  An array of identical elements with identical magnitudes and with a progressive phase is called a uniform array.
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  Circular Array  antennaelements arranged around a circular ring.  Applications are radio direction finding, air and space navigation, underground propagation, radar, sonar.
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   Unlike lineararrays, circular arrays can provide a 2D angular scan, both horizontal φ and vertical θ scans.  Unlike 2D planar arrays, circular arrays are basically 1D linear arrays but in a circular form.  Unlike linear arrays, a circular array can scan horizontally for 360° with no distortions near the end- fire directions.
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  Planar arrays  Planararrays are more versatile  Antenna elements arranged over some planar surface (example - rectangular array).  provide more symmetrical patterns with lower side lobes  much higher directivity (narrow main beam).  Applications – tracking radars, remote sensing, and communications.