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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 ...
An optical phased array (OPA) is the optical analog of a radio-wave phased array. [1] By dynamically controlling the optical properties of a surface on a microscopic scale, it is possible to steer the direction of light beams (in an OPA transmitter [ 2 ] ), or the view direction of sensors (in an OPA receiver [ 3 ] ), without any moving parts.
A typical radiation pattern of phased arrays whose inter-element spacing is greater than half a wavelength, hence the radiation pattern has grating lobes.. For discrete aperture antennas (such as phased arrays) in which the element spacing is greater than a half wavelength, a spatial aliasing effect allows plane waves incident to the array from visible angles other than the desired direction ...
This subsection could also be named "phased arrays", a type of composite directional antenna where the various component simple antennas are laid out a large fraction of a wavelength apart, with each antenna's feedline's phase individually shifted, so that the signal from a radio wave moving in some selected direction across the layout of the ...
A broadside array is a one or two dimensional array in which the direction of radiation of the radio waves is perpendicular to the plane of the antennas. To radiate perpendicularly, the antennas must be fed in phase. An endfire array is a linear array in which the direction of radiation is along the line of the antennas. The antennas must be ...
For a planar array, these sub-arrays would be the four quadrants of the array, each with 1/4 of the array's elements. In a linear array, the output of each sub-array is summed to form the "sum" channel, and the same outputs are subtracted to form the "del" channel.
In 1959, DARPA developed an experimental phased array radar called Electronically Steered Array Radar (ESAR). It was a large two-dimensional phased array with beam steering controlled by computers instead of requiring mechanical motion of the antenna. The first module, a linear array, was completed in 1960. It formed the basis of the AN/FPS-85. [1]
For discrete aperture antennas (such as phased arrays) in which the element spacing is greater than a half wavelength, the spatial aliasing effect causes some sidelobes to become substantially larger in amplitude, and approaching the level of the main lobe; these are called grating lobes, and they are either identical, or nearly identical as shown in the figure, copies of the main beams.