Topic
Active antenna
About: Active antenna is a research topic. Over the lifetime, 2246 publications have been published within this topic receiving 26493 citations.
Papers published on a yearly basis
Papers
More filters
05 Jul 2008
TL;DR: In this paper, a reconfigurable antenna which excites orthogonal a circular polarization is proposed and the behavior and the characteristics of the antenna are experimentaly investigated and the proposed antenna has the cross slot at the center of the patch, and four diodes are embedded in a star form across the slot.
Abstract: In this paper, the reconfigurable antenna which excites orthogonal a circular polarization is proposed and the behavior and the characteristics of the antenna are experimentaly investigated. The proposed antenna has the cross slot at the center of the patch, and four diodes are embedded in a star form across the slot. A circular polarization is excited though in a wide band due to the nonlinearity of the diodes. When the bias voltage Vc superimposed on the RF signal is a slighty positive near 0 V, a LHCP is achieved. On the other hand, when Vc is a slightly negative near 0 V, a RHCP is achieved. Therefore, it is easily possible to switch the phase difference of plusmn90 degrees by a bias voltage Vc for those diodes in a wide band. As a result, switchable circular polarization antennas can be achieved in a wide frequency band. The proposed antennas are practically attractive for the wireless communications as a circularly polarized active antenna.
10 citations
20 Jun 2004
TL;DR: In this paper, a scaling approach has been used for the electromagnetic modeling of an active element integrated with a radiating structure, from the small size of the active element to the large planar radiating surface, many scale levels are present in an active antenna.
Abstract: In this paper, a scaling approach has been used for the electromagnetic modeling of an active element integrated with a radiating structure. From the small size of the active element to the large planar radiating surface, many scale levels are present in an active antenna. We propose a new technique for taking into account the multi-scale nature of such structure in electromagnetic simulations. A N-port is first computed in order to model the active antenna at a given scale level. Then the cascade of these N-ports allows the electromagnetic modeling of the overall antenna. The computation of the driving-point impedance and the current distribution on an active antenna are presented and compared with classical simulation techniques. Accurate numerical results are obtained with a substantial reduction in computer time and memory compared to direct full-wave electromagnetic analysis.
10 citations
Journal Article•
TL;DR: In this article, an active ferrite loop antenna is proposed as an internal replacement/complement with a performance of -23 dB degradation compared to a full-size lossless dipole in urban environments.
Abstract: This thesis presents solutions and studies related to the design of wideband antennas for wireless handheld terminal applications. A method of electrically shortening the terminal chassis length to obtain resonance at high frequencies has been proposed and evaluated, thereby increasing the antennas impedance bandwidth. No significant effect on the lower frequency band in a dual-band antenna prototype has been observed, making the method suitable for multi-band applications. The chassis has further been utilized as a zero-thickness 0.9 - 2.7 GHz high efficiency antenna by inserting a notch in the chassis center, and a feasibility study for typical phones has been performed. Additionally, the effect of talk position on the chassis wave-mode has been investigated, where the standard equivalent circuit model for terminal antennas has been modified to include the presence of the users head. The model has been used to explain measured and simulated effects concerning frequency detuning, efficiency reduction and bandwidth enhancements when the terminal is placed in talk position.The use of a hands-free earpiece cord is currently mandatory for FM radio reception as the cord is utilized as antenna. However, there is currently a market driven demand for removing the cord requirement since many modern phones are equipped with speakers and Bluetooth headsets. In this thesis, an active ferrite loop antenna is proposed as an internal replacement/complement with a performance of -23 dB (G/T degradation) compared to a full-size lossless dipole in urban environments. Also, a modification to the cord is suggested for DVB H reception.Complex matching networks have been investigated to increase the bandwidth of dual band PIFA antennas, and a printed dual band dipole has been integrated with a modified Marchand balun for dual resonance at two separate frequency bands, thus covering the commercial cellular bands 824-960 and 1710-2170 MHz with a single antenna.
10 citations
22 Jun 2003
TL;DR: In this paper, the authors present an application of GA to the synthesis of an active phased array antenna for a geostationary satellite, which consists in finding the control coefficients (in terms of amplitude and phase) to be applied on each radiating element to obtain a desired coverage on the Earth.
Abstract: We present an application of GA to the synthesis of an active phased array antenna for a geostationary satellite. The problem consists in finding the control coefficients (in terms of amplitude and phase) to be applied on each radiating element to obtain a desired coverage on the Earth. The technological and operational constraints could be taken into account.
10 citations
TL;DR: In this paper, a UDR feed circuit is implemented by microstrip lines and aperture-coupling is studied experimentally for arrays of two, four and eight radiators.
Abstract: In this paper, design considerations and experimental investigations of an integrated active antenna for space power combining that makes use of unidirectional dielectric radiators (UDRs) are presented and discussed. Attractive electrical performance stemming from proprieties of nonradiating dielectric waveguide structures is used to design a prototype at a frequency of 14 GHz. A UDR feed circuit is implemented by microstrip lines and aperture-coupling is studied experimentally for arrays of two, four and eight radiators. Measurements show high coupling and radiation efficiencies of the proposed excitation method. A power-combining efficiency of 89% was measured and a gain of 23.1 dBi was achieved for an antenna with eight radiators and four amplifiers. It is also shown that such a circuit configuration allows the combination of planar Ku-band monolithic hybrid microwave integrated circuit and UDR components in flexible design of active array antennas.
10 citations