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The far-field pattern of an antenna may be determined experimentally at an antenna range, or alternatively, the near-field pattern may be found using a near-field scanner, and the radiation pattern deduced from it by computation. [1] The far-field radiation pattern can also be calculated from the antenna shape by computer programs such as NEC.
Fixed phased arrays incorporate fixed phase shifters. For example, most commercial FM Radio and TV antenna towers use a collinear antenna array, which is a fixed phased array of dipole elements. In radar applications, this kind of phased array is physically moved during the track and scan process. There are two configurations.
The Eurofighter Typhoon combat aircraft with its nose fairing removed, revealing its Euroradar CAPTOR AESA radar antenna. An active electronically scanned array (AESA) is a type of phased array antenna, which is a computer-controlled antenna array in which the beam of radio waves can be electronically steered to point in different directions without moving the antenna. [1]
Animation showing how a passive electronically scanned array works. It consists of an array of antenna elements (A) powered by a single transmitter (TX). The feed current for each antenna passes through a phase shifter (φ) controlled by a computer (C). The moving red lines show the wavefronts of the radio waves emitted by each element.
Digital antenna array (receiver segment) Digital antenna array (transmitter part) Digital antenna array (DAA) is a smart antenna with multi channels digital beamforming, usually by using fast Fourier transform (FFT). The development and practical realization of digital antenna arrays theory started in 1962 under the guidance of Vladimir Varyukhin .
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.
It consists of multiple dipoles in a two-dimensional array, each fed through an electronic phase shifter, with the phase shifters controlled by a computer control system. The beam can be instantly pointed in any direction over a wide angle in front of the antenna. Used for military radar and jamming systems. Adcock antenna
Antenna gain (G) is defined as antenna efficiency (e) multiplied by antenna directivity (D) which is expressed mathematically as: =. A useful relationship between omnidirectional radiation pattern directivity (D) in decibels and half-power beamwidth (HPBW) based on the assumption of a sin ( b θ ) / b θ {\displaystyle \sin(b\theta )/{b ...