An antenna array is a configuration of multiple antennas (elements) arranged to achieve a given radiation pattern. A single-element antenna is usually not enough to achieve technical needs. That happens because its performance is limited. The set of discrete elements, which constitute an antenna array, offers the solution to the transmission and/or reception of electromagnetic energy. The geometry and the type of elements characterize an antenna array. Antenna array factor quantifies the effect of combining radiating elements in an array without the element specific radiation pattern taken into account. The overall radiation pattern of an array is determined by this array factor combined with the radiation pattern of the antenna element. The overall radiation pattern results in a certain directivity and thus gain linked through the efficiency with the directivity. Directivity and gain are equal if the efficiency is 100%.
Classification
The phasing of the uniform linear array elements may be chosen such that the main lobe of the array pattern lies along the array axis (end-fire array) or normal to the array axis (broadside array).
Broad side array
Broad side array is the arrangement of identical antennas, which are placed along the axis perpendicular to the direction of maximum radiation. The identical antennas are equally spaced along the line of axis and all the elements are fed with equal magnitude of current with the same phase. This results in array pattern known as broad side array. It is evident that broad side array is bidirectional where maximum radiation is obtained in the direction of axis perpendicular to the array axis. By placing an identical array at a distance of λ/4 behind the array, bidirectional array can be converted to unidirectional array and by lead current in phase by λ/2.
End Fire Array
An End fire array looks similar to broad side array except that the individual elements are fed with the current that is equal in magnitude but opposite in phase. In other words, the individual elements are excited in such a way that a progressive phase difference between adjacent elements becomes equal to the spacing between the antennas (elements). “The arranging of identical antennas along a line drawn perpendicular to their respective axis so that the principle direction of radiation coincides with the direction of the axis of array” is known as End fire array. The radiation is maximum in the direction along the axis of the array i.e., 0 degree (or) 180 degree. If two equal radiators are operated in phase quadrature at a distance of λ/4 apart, an end fire couplet is said to be formed.
Classification
The phasing of the uniform linear array elements may be chosen such that the main lobe of the array pattern lies along the array axis (end-fire array) or normal to the array axis (broadside array).
Broad side array
Broad side array is the arrangement of identical antennas, which are placed along the axis perpendicular to the direction of maximum radiation. The identical antennas are equally spaced along the line of axis and all the elements are fed with equal magnitude of current with the same phase. This results in array pattern known as broad side array. It is evident that broad side array is bidirectional where maximum radiation is obtained in the direction of axis perpendicular to the array axis. By placing an identical array at a distance of λ/4 behind the array, bidirectional array can be converted to unidirectional array and by lead current in phase by λ/2.
End Fire Array
An End fire array looks similar to broad side array except that the individual elements are fed with the current that is equal in magnitude but opposite in phase. In other words, the individual elements are excited in such a way that a progressive phase difference between adjacent elements becomes equal to the spacing between the antennas (elements). “The arranging of identical antennas along a line drawn perpendicular to their respective axis so that the principle direction of radiation coincides with the direction of the axis of array” is known as End fire array. The radiation is maximum in the direction along the axis of the array i.e., 0 degree (or) 180 degree. If two equal radiators are operated in phase quadrature at a distance of λ/4 apart, an end fire couplet is said to be formed.
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