Active antenna

About: Active antenna is a research topic. Over the lifetime, 2246 publications have been published within this topic receiving 26493 citations.

Compact phased array millimeter wave communications systems suitable for fixed wireless access applications

Abstract: Millimeter wave communications system include an RF printed circuit board structure that includes a phased array antenna that has a plurality of radiating elements and a channel block that includes a plurality of active antenna channels that each feed a respective one of a plurality of sub-groups of the radiating elements. A first sub-set of the active antenna channels are completely positioned on a first side of the phased array antenna and a second sub-set of the active antenna channels each include a first portion that is on a second side of the phased array antenna, the second side being adjacent the first side.

Study of active antenna receivers and calibration method for digital beamforming

Abstract: In next-generation high speed wireless communications, the development of digital beamforming (DBF) is indispensable for the creation of base stations and terminal antennas with high functionality, low cost. and small size. On the other hand, active antennas that combine a passive antenna and active devices are advantageous for use in DBF, because the feed line can be shortened and phase and amplitude imbalance among the array branch elements can be reduced. Further, if technologies to reduce the number of active devices, such as the direct conversion and Low IF schemes, are combined, it is possible to attempt miniaturization and reduction of individual differences. In this paper, a receiver of small size for DBF is proposed and experimentally studied by using an active integrated antenna containing an amplifier and a Low IF scheme. A calibration circuit for amplitude and phase corrections is discussed in which the error factors in the characteristics between the devices are taken into account. Further, experimental results on beam pattern generation by the test system in an anechoic chamber are presented. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(11): 20–29, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10119

EHF phased array manpack terminal design

Abstract: A requirement exists to provide a full duplex, 24-kb/s MILSATCOM voice circuits with low probability of intercept and antijam protection to highly mobile tactical users The authors discuss an EHF manpack terminal design that uses moderate beamwidth antennas to provide this service The terminal antenna system consists of five transmit/receive pairs of phased array antennas mounted on the faces of a cube A hybrid inertial motion sensing/antenna step tracking system is used to select the active antenna array and point the selected beam toward the satellite despite the presence of user motion The recommended terminal design relies on technologies that are currently under development The realization of a cost-effective implementation is considered feasible within the next five years, but would require continued investment in MMIC (monolithic microwave integrated circuit) phased array technology and manufacturing techniques >

Use of variable phase-shifters based on Injection Locked Harmonic Self­ Oscillating Mixers in Active Antenna Arrays. (Invited Paper)

Abstract: A receiving 4x1 element antenna array based on Injection-Locked Harmonic Self-Oscillating Mixers has been presented. With the proposed topology, coupling problems between different IL3HSOM circuits, sometimes present in oscillator based phased array systems, have been avoided by filtering without affecting the IF output power of the phased antenna array. Using a progressive phasedistribution along the array elements, the beam scanning behavior has been simulated and measured, obtaining a beam scanning range between −23° and 23°.

The structure of antenna polypeptides from phototropic bacteria

Abstract: In photosynthesis light energy is converted into a photochemical potential by means of the cooperative action of the light-harvesting antennae and the reaction centers. The antenna system, which is composed of various antenna complexes, funnels excited-state energy via a heterogene­ ous and direction-oriented energy transfer system to the reaction center with little energy dissipation. It is generally assumed that_I~ergy mi­ grates from pigment molecule to pigment molecule within ~ 10 Sand reaches the reaction centers by random walk between the pigments within ~ 10-11S. It may also be postulated that practically all photons absorbed form mobile electronic excited singlet (S ) states called excitons in the antenna complexes. The formation of large~ (localized)excitons by strong exciton coupling between pigments and/or Forster type energy migration by weak coupling is discussed. To understand the physical mechanism and the theoretical basis of the directed energy transfer to the reaction center, knowledge of the structure and, particularly, general structural principles of the antenna systems are important. Such general principles are best derived from comparison of diverse antenna structures. Of special interest is the question as to which structural elements within the wide variety of antenna systems are invariant and are therefore of functional importance. Fundamental to the formation of the functionally active antenna com­ plexes (pigment-protein complexes) and finally of the whole antenna are the structure and organization of the antenna polypeptides (1, 2). Structu­ ral and functional analysis revealed the following general features of the whole antenna complexes with respect to the role of the antenna polypeptides: 1.) All pigment molecules are specifically bound to polypeptides and form defined antenna complexes with a precise number of pigments (2-7 pigments per polypeptide in bacteria, cyanobacteria). 2.) The polypeptides determine the position, orientation, spacing and environment (spectral shift) of the pigment molecules. 3.) The specific arrangement (aggregation) of a large number of relatively small polypeptides (bacteria: 5-7 kD, cyanobacteria: 18-25 kD) forms the basis of the three-dimensional structure of the antenna complexes,