Showing papers on "Active antenna published in 2003"

Aperiodic array antenna

Abstract: An antenna array that uses at least two passive antennas and one active antenna disposed above a ground plane, but electrically isolated from the ground plane, and a respective resonant strip positioned beneath each passive antenna. The passive antenna elements are positioned about the active element, and each of the at least two passive antenna elements is individually set to a reflective or a transmissive mode to change the characteristics of an input/output beam pattern of the antenna apparatus.

Reconfigurable antennas for wireless devices

Abstract: New technologies in communications electronics, such as software-defined radio (SDR) and RF switches implemented using micro-electromechanical systems (MEMS), present new challenges and opportunities for antenna design. In sharp contrast to digital technology where Moore's law reigns, a fundamental law of physics constrains the ability to realize electrically small antennas that are both efficient and broadband. As a result, covering several frequency bands concurrently with a single antenna having enough efficiency and bandwidth is a major challenge. One possible solution to this problem is to use reconfigurable antennas that tune to different frequency bands. Such an antenna would not cover all bands simultaneously, but provides narrower instantaneous bandwidths that are dynamically selectable at higher efficiency than conventional antennas. Such tunable-antenna technology is an enabler for software-definable radios, the RF front ends of which must be reprogrammable on the fly. This paper discusses the practical implementation issues, limitations, and measured results of small, narrowband, tunable antennas within portable handsets. Many of the concepts discussed in this paper will likely become practical and cost effective in the near future because of recent advances in RF MEMS switches.

Low cost multiple pattern antenna for use with multiple receiver systems

Abstract: An antenna assembly includes at least two active or main radiating omni-directional antenna elements arranged with at least one beam control or passive antenna element used as a reflector. The beam control antenna element(s) may have multiple reactance elements that can electrically terminate it to adjust the input or output beam pattern(s) produced by the combination of the active antenna elements and the beam control antenna element(s). More specifically, the beam control antenna element(s) may be coupled to different terminating reactances to change beam characteristics, such as the directivity and angular beamwidth. Processing may be employed to select which terminating reactance to use. Consequently, the radiator pattern of the antenna can be more easily directed towards a specific target receiver/transmitter, reduce signal-to-noise interference levels, and/or increase gain by using Radio Frequency (RF), Intermediate Frequency (IF), or baseband processing. A Multiple-Input, Multiple-Output (MIMO) processing technique may be employed to operate the antenna assembly with simultaneous beam patterns.

Closely coupling amplifiers to antennas on a base station tower

Abstract: The present invention relates to a transmit diversity antenna system employing active antenna electronics (with both receive and transmit amplifiers distributed among the elements of the antenna), polarization diversity on receive, and polarity diversity along with time delay diversity on transmit. The combination of these three techniques, in wireless communications applications, improves the efficiency and performance of both the transmitted and received signals at a base station, as well as the received signal at the mobile. In practice the present invention enables a substantially "balanced link" to exist between the base station and a mobile.

A differential active patch antenna element for array applications

Abstract: This letter describes the implementation of an active receiving antenna at 5-6 GHz. An aperture-coupled patch antenna is designed to provide a differential interface toward monolithically integrated circuits. The integration with a low-noise amplifier is shown. The proposed structure offers new advantages for the construction of compact and robust adaptive antenna arrays. Measurements show around 5.5 dBi antenna gain with a cross-polarization below -27 dB. The differential low-noise amplifier provides more than 10 dB gain improvement.

Mobile communication handset with adaptive antenna array

Abstract: A mobile communication handset includes at least one passive antenna element and an active antenna element adjacent to the passive antenna elements protruding from a housing. The active element is coupled to electronic radio communication circuits and the passive antenna elements are coupled to circuit elements that affect the directivity of communication signals coupled to the antenna elements.

A harmonic suppression antenna for an active integrated antenna

Abstract: An inset-fed antenna with a shorting pin and slots is presented for harmonic suppression of an active integrated antenna. Its fundamental resonant frequency is 5.8 GHz. At fundamental and harmonic frequencies, return loss and radiation characteristics are measured and compared with those of the conventional microstrip patch antenna. The second and third harmonic return losses of the proposed antenna are suppressed to 6.7 dB and 17.7 dB with respect to the conventional patch antenna, respectively.

Wide scanning phased array antenna design in Ka band

Abstract: A millimetre wave active phased array antenna has been developed that is capable of wide scanning angle in both E- and H-planes with small deviation in antenna gain In order to solve this problem, a dipole antenna with parasitic element has been adopted, which may have the capability of adjusting the influence of mutual coupling in the array element pattern The design of the parasitic element is examined and the effect of its shape on pattern characteristics is confirmed by experiment Beam scanning angles of ±573 degrees in the E-plane and ±682 degrees in the H-plane were obtained for each array antenna pattern

Study of deployed and modular active phased-array multibeam satellite antenna

Abstract: A deployed, self-cooled and modular (tile-based) active phased array for multibeam applications has recently been proposed in the literature. This novel antenna facilitates the implementation of large array antennas in space with many beams from the same aperture, offering a flexible payload with the potential for high traffic capacity. However, the configuration also raises some questions about degradation in antenna performance, due to constraints such as non-circular aperture, frame gap, uniform amplitude excitation, and a calibration boom deployed in front of the array. Methods dealing with these issues are discussed in this paper. It is shown that a phase-only optimization technique can effectively reduce interference between same-frequency spatially reused beams, and can compensate for EIRP and C/I degradation for tile-correlated errors and failures.

An integrated active microstrip reflectarray element with an internal amplifier

Abstract: A new active microstrip reflectarray element (unit cell) with an internal microwave integrated circuit amplifier is introduced. The amplifier resides in a small slot within the footprint of the square patch antenna and is connected between the feed points for the patch's orthogonal polarizations. This element results in reduced array element spacing, reduced transmission line losses through elimination of long feed lines, and a simplified fabrication process compared to other active reflectarray unit cells. Patch geometries with several slot shapes are studied with simulations to arrive at an antenna configuration with good return loss and isolation characteristics. The stability and gain of the system are analyzed over frequency. Measured radiation pattern and gain data for a single element and a small array agree well with predictions and demonstrate the element's capabilities. Limitations of the active element, approaches to mitigate these limitations, and directions for future work are discussed.

Thirty-Element Active Antenna Array as a Prototype of a Huge Low-Frequency Radio Telescope

Abstract: An effective wide-band (10 to 60 MHz) active antenna element has been developed. The cost of one short (3 m), thin dipole with built-in amplifier and metal construction is less than 45 euro. It was shown both theoretically and experimentally that the upper limiting frequency is at least 60 MHz, the dynamic range is 90 dB/μV and the share of the amplifier noise to the background antenna temperature is about 10%. The developed active dipole was tested by building a 30-element antenna array and comparing its parameters with one of the subpart of the UTR-2 radio telescope having passive dipoles of 8.6 m in length and 1.8 m in diameter. The 3C461 ionospheric scintillation spectra observed in the experiments show that the sensitivities and noise-immunities of both antennas are close. This proves the availability using of a short cheap active dipole in new generation giant radio telescopes.

Beamforming using a backplane and passive antenna element

Abstract: An active antenna element to transmit and/or receive RF (Radio Frequency) signals is positioned in relation to a backplane that reflects RF signals. One or more passive antenna elements can be disposed on a similar side of the backplane as the active antenna element. Settings of the one or more passive antenna elements are adjusted to produce an input/output beam pattern that varies depending on whether the at least one passive antenna element is reflective or transmissive. Based on this technique, an RF input output beam pattern of an antenna assembly including the backplane, active antenna element and passive antenna elements can be controlled for better reception and transmission of RF signals.

Architecture and interconnect technologies for a novel conformal active phased array radar module

Abstract: Highly integrated transmit/receive modules are key components for modern active phased array radar systems. This paper describes architecture and related interconnect technologies for a novel transmit/receive module with integrated radiating element and circulator for X-band applications. It allows the realization of future planar or conformal active antenna arrays with low installation depth as well as high maintainability performance.

Multiple pattern antenna

Abstract: An antenna assembly includes at least two active or main radiating omni-directional antenna elements (100-1, 100-2) arranged with at least one beam control or passive antenna element (115) used as a reflector (305). The beam control antenna element(s) (115) may have multiple reactance elements (150-1, 150-2) that can electrically terminate it to adjust the input or output beam pattern(s) (180, 190) produced by the combination of the active antenna elements (100-1, 100-2) and the beam control antenna element(s) (115). More specifically, the beam control antenna element(s) (115) may be coupled to different terminating reactances (150-1, 150-2) to change beam characteristics, such as the directivity and angular beamwidth. Processing may be employed to select which terminating reactance to use.

Active broad-band reception antenna with reception level regulation

Abstract: An active broad-band reception antenna, in which the internal amplification of the active antenna is lowered if a predetermined signal level is exceeded, and which consists of a passive antenna part having output connectors that are connected with the input connectors of an amplifier circuit. The input circuit of the amplifier circuit contains a three-pole amplification element with its impedance control connector being connected with the first connector of the passive antenna part, at high frequency. The input admittance of a transformation network having the nature of a low loss filter for low amplitude, high-frequency reception signals, has a counter-coupling and linearizing effect in the high-frequency connection between the source connector of the three-pole amplification element and the second connector of the passive antenna part. The transformation network is loaded with a continuing circuit at its output. There is at least one adjustable electronic element, responsive to a control amplifier connected to the output of the active amplifier for adjustably lowering the reception level, and disposed in the transformation network, so that the input admittance of the transformation network, that has the linearizing effect, is reduced, if there is a reduction of the high-frequency reception signal.

Active antenna method and system with variable directivity and gain

Abstract: A wireless mobile communication system comprising a variable beam antenna system having a beam width and a direction; a variable beam antenna controller for controlling the beam width and direction of the variable beam antenna system and for receiving a communication link quality indication; and a predetermined trigger for measuring the communication link quality indication in at least one beam width position and positioning the beam width in a direction corresponding with a maximum communication link quality. The active, variable gain antenna system has the ability to compensate for deep-fades inside a building. Typically, the primary cause for dropped-calls inside buildings is due to deep fades inside buildings.

Compact, wide-band, integrated active module for radar and communication systems

Abstract: An integrated module (14) for an active antenna assembly is disclosed. The integrated module is switchable between a receive mode and a transmit mode and includes active components and a dual input wideband balun (34). The active components includes amplifiers (26, 36) and micro electro-mechanical system (MEMS) switches (22, 24). The integrated module is adapted for positioning directly behind a radiator of an antenna array.

5-6 GHz low-noise active antenna array for multi-dimensional channel-sounding

Abstract: The design and measurement of a 5-6 GHz active receiving antenna array is presented. To obtain a compact and robust design, active downconverters are monolithically integrated using a standard 0.6 /spl mu/m-MESFET process and combined with planar linearly polarized aperture-coupled patch antennas. A very low noise figure of 3.5 dB and a total conversion gain of 30 dB is achieved. The use of dedicated monolithically integrated components leads to very low gain and phase variations. This active array will be used in a multi dimensional channel sounder.

Application of microwave radiometry for buried landmine detection

Abstract: In this paper we illustrate the phenomenological background, the design, and some experimental results of a multi-spectral low frequency microwave radiometer as a part of a multi-sensor mine detection system. The overall system is intended to work in a hand-held operation allowing the use in areas of difficult access without excluding missions in more friendly environments. Thus the radiometer antenna is operated in an extreme near-field mode to achieve a corresponding ground resolution in the order of the active antenna aperture size. In particular, the radiometer receiver is swept in low-bandwidth steps through a broad microwave (MW) frequency range to vary the penetration depth and the reflectivity properties of the actually observed ground part. This can provide significantly increased information about the location and shape of buried objects for discrimination purposes. The relevant theoretical aspects of this interference based effects are illustrated and attempts to interpret the spectrum for specific layered arrangements as in the case of buried objects are presented.

Wideband active antenna

Abstract: The objective of this work is to develop novel antenna designs for bandwidth enhancement using passive and active log periodic techniques. The first part of the thesis describes the integration of amplifiers with single microstrip patch antennas. The antennas have been designed at centre frequencies of 2.1 GHz and 2.6 GHz. There are four different configurations of the antenna and amplifier. The second part describes the passive log periodic technique. Antennas with different numbers of elements have been modelled using microstip lines and S parameter data from the single element. This data is extracted from the Momentum simulation and combined with the microstrip transmission line. The comparison between circuit and Momentum simulation shows very good agreement. The fabrication of the inset feed passive log periodic antenna has been done with four different numbers of elements: five, seven, nine and eleven. The centre frequencies of the antennas have been designed at 3 GHz with a bandwidth of 1.8 GHz for eleven elements LPA. The properties of the antennas such as bandwidth, gain, cross-polar isolation and half power beamwidth have been investigated and compared between different elements. The last part of the thesis is the integration of the amplifier with the log periodic antenna. The antennas have been designed with a bandwidth of 1 GHz with a centre fiequency of 3 GHz. Five different configurations have been investigated. The first configuration involves the integration of a single amplifier at the input of the feed line of a five element LPA. The , second configuration involves the integration of an amplifier in the middle of the five element LPA. The third configuration is a five element LPA with individual amplifiers in each element. In the fourth configuration, individual amplifiers and filters are integrated with five elements. The last configuration involves the integration of a single amplifier with a seven element LPA at the input to the feed line of the antenna The performance of these configurations have been investigated and compared in terms of bandwidth, gain relative to a passive LPA, cross polar isolation and beamwidth.

Active antenna coverage synthesis for GEO satellite using genetic algorithm

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.

Forward-link soft-handoff in CDMA with multiple-antenna selection and fast joint power control

Abstract: We consider forward-link soft-handoff with multiple antenna selection and fast joint power control at high data rates in a cellular code-division multiple-access network, where signals are directed to a mobile station (MS) from antennas located at the same or different base stations. The total power transmitted to any mobile is divided among the active antennas selected according to the momentary channel conditions so as to maximize the signal-interference ratio at each MS. Multiple-antenna selection is used to mitigate the effects of both short- and long-term fading, and achieve the best soft-handoff with respect to system capacity and complexity. To achieve capacity gains with soft-handoff, we derive optimum handoff thresholds corresponding to the optimum handoff region in different cell environments. Numerical results demonstrate that under high Doppler spread and large handoff-delay conditions, the proposed soft-handoff employing two transmit antennas and the optimum handoff threshold achieves a significant gain in microcell environments, but not in macrocell environments.

A novel H-shaped active integrated antenna

Abstract: A novel H-shaped oscillating patch antenna is proposed. In this approach, the H-shaped antenna can serve as a filter, an output matching circuit, and a harmonic tuner in addition to being a load and a radiating element. A prototype is designed, fabricated and tested at 3.65 GHz. Measurement results reveal a 41 dB rejection in the second harmonic radiation. Compared to the one using a rectangular patch, our design shows a size reduction of up to 30%. This active antenna is shown to be a good candidate as an element for a highly compact oscillating array for power combining and radar applications.

L-band active receiving antenna for automotive applications

Abstract: This paper describes L-band active receiving antenna for the automotive applications (DAB radio). The antenna is based on a printed dipole in 1452-1492 MHz frequency range and has a low noise amplifier. Two different versions of the antenna are presented: one for “on-vehicle” application (roof or trunk) and the second one for “in-vehicle” application (glass window). Antenna directionality is measured for on-vehicle and in-vehicle antenna locations. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 319–323, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11203

Planar inverted-F antennas as an inverse class-F termination for wireless applications

Abstract: We present an electrically small antenna for use with high-efficiency power amplifiers for wireless applications. A planar inverted-F antenna (PIFA) design is shown that is optimized to provide an inverse class-F load termination for use at the output of a field effect transistor (FET) for optimum output power and efficiency. A power-added efficiency in excess of 60% was also measured for an active PIFA.

5-6 GHz monolithically integrated calibratable low-noise downconverter for smart antenna arrays

Abstract: An integrated downconverter for active antenna arrays is presented. From 5.125 GHz to 5.875 GHz the downconverter shows more than 20 dB conversion gain and a noise figure of less than 3.8 dB with a minimum of 3.3 dB. Input 1 dB compression point is -18 dBm. Image rejection better than 35 dB is achieved using an integrated lumped-element bandpass filter. A switchable symmetric input amplifier is proposed to calibrate amplitude and phase errors without degrading the noise figure.

Receiving antenna for multibeam coverage

Abstract: The invention relates to a receiving antenna for satellite telecommunications. More specifically, the invention relates to an active antenna comprising a network of elementary sources which is positioned at the focal point of a focusing reflector. According to the invention, said network of sources is disposed on a more or less spherical, concave surface S. The aforementioned arrangement can be used to: (i) improve the efficiency of the optics and (ii) enable the use of polarisation duplexers behind surface S in order to increase the spectral efficiency of the antenna.

Highly sensitive, co-optimised active receiver antenna: its use in Dopplerradar in 2.4 GHz ISM band

Abstract: A novel design methodology is presented to co-optimise an active receiver antenna, combining a planar rectangular ring antenna and a low noise amplifier, operating from 2.4 to 2.485 GHz. A Doppler radar experiment based on this active antenna illustrates the excellent noise performance resulting from this approach.

Nontracking antenna performance for inertially controlled spacecraft using TDRSS

Abstract: A series of tests to validate an antenna pointing concept for spin-stabilized satellites using a data relay satellite is described. These tests show that proper antenna pointing on an inertially stabilized spacecraft can lead to significant access time through the relay satellite even without active antenna pointing. We summarize the test results, the simulations to model the effects of antenna pattern and space loss, and the expected contact times. We also show how antenna beam width affects the results.