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Most antennas boresight axis is fixed by their shape and cannot be changed. However phased array antennas can electronically steer the beam, changing the angle of the boresight by shifting the relative phase of the radio waves emitted by different antenna elements, and even radiate beams in multiple directions (multiple boresights). [1]
In a conventional phased array the individual antenna elements are mounted on a flat surface. In a conformal antenna, they are mounted on a curved surface, and the phase shifters also compensate for the different phase shifts caused by the varying path lengths of the radio waves due to the location of the individual antennas on the curved surface.
In a radio antennas, the main lobe or main beam is the region of the radiation pattern containing the highest power or exhibiting the greatest field strength.. The radiation pattern of most antennas shows a pattern of "lobes" at various directions, where the radiated signal strength reaches a local maximum, separated by "nulls", at which the radiation falls to zero.
An active phased array or active electronically scanned array (AESA) is a phased array in which each antenna element has an analog transmitter/receiver (T/R) module [13] which creates the phase shifting required to electronically steer the antenna beam. Active arrays are a more advanced, second-generation phased-array technology that are used ...
Similarly, a lens-enhanced phased array antenna, similar to a transmitarray, has been demonstrated. [19] By combining the beam steering capabilities of phased arrays and the focusing properties of transmitarrays, this hybrid antenna has a smaller form factor, [20] and steers to ±45° in both planes with a 3.2 dB increase in directivity at
and is the phase shift introduced by th unit cell of reflect array to its reflected field relative to the incident field. For a feed horn located at ( 0 , 0 , F ) {\displaystyle (0,0,F)} , the formula for the optimal phase distribution on a conventional reflectarray for a beam in the boresight direction is given by:
Beam steering is a technique for changing the direction of the main lobe of a radiation pattern.. In radio and radar systems, beam steering may be accomplished by switching the antenna elements or by changing the relative phases of the RF signals driving the elements.
A Butler matrix is a beamforming network used to feed a phased array of antenna elements. Its purpose is to control the direction of a beam, or beams, of radio transmission . It consists of an n × n {\displaystyle n\times n} matrix ( n {\displaystyle n} some power of two) with hybrid couplers and fixed-value phase shifters at the junctions.