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Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. [1] This is achieved by combining elements in an antenna array in such a way that signals at particular angles experience constructive interference while others experience destructive interference.
Smart antennas (also known as adaptive array antennas, digital antenna arrays, multiple antennas and, recently, MIMO) are antenna arrays with smart signal processing algorithms used to identify spatial signal signatures such as the direction of arrival (DOA) of the signal, and use them to calculate beamforming vectors which are used to track and locate the antenna beam on the mobile/target.
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.
Transposed Block Face-splitting product in the model of a Multi-Face radar with DAA, proposed by V. Slyusar in 1996 [5]. The main approach to digital signal processing in DAA is the "digital beamforming" after Analog-to-digital converters (ADC) of receiver channels or before Digital-to-analog converters (DAC) by transmission.
Phased arrays take multiple forms. However, the four most common are the passive electronically scanned array (PESA), active electronically scanned array (AESA), hybrid beam forming phased array, and digital beam forming (DBF) array.
Precoding is a generalization of beamforming to support multi-stream (or multi-layer) transmission in multi-antenna wireless communications. In conventional single-stream beamforming, the same signal is emitted from each of the transmit antennas with appropriate weighting (phase and gain) such that the signal power is maximized at the receiver output.
An adaptive beamforming system relies on principles of wave propagation and phase relationships. See Constructive interference, and Beamforming.Using the principles of superimposing waves, a higher or lower amplitude wave is created (e.g. by delaying and weighting the signal received).
The goal is to perform beamforming such that the beam appears stationary as the airborne radar is in motion over discrete time periods so the clutter appears without Doppler. [2] However, phase errors can cause significant degradation since the algorithm is not adaptive to the returned data. [2]