Showing papers on "Active antenna published in 2009"

Non-Foster Impedance Matching of Electrically-Small Antennas

Abstract: Electrically-small antennas present high-Q impedances characterized by large reactances and small radiation resistances. For such antennas, the effectiveness of passive matching is severely limited by gain-bandwidth theory, which predicts narrow bandwidths and/or poor gain. With receivers, the inability to resolve this impedance mismatch results in poor signal-to-noise (S/N) ratio, as compared to using a full-size antenna. With transmitters, the consequence is poor power efficiency. However, in many applications full-size antennas are impractical, and a means is required to effectively match their electrically-small counterparts. This paper presents the technique of non-Foster impedance matching, which employs active networks of negative inductors and capacitors to bypass the restrictions of gain-bandwidth theory. We first review the origins and development of non-Foster impedance matching, and then present experimental results for the non-Foster impedance matching of electrically-small dipoles and monopoles. For receivers, our best measurements on the antenna range demonstrate up to 20 dB improvement in S/N over 20-120 MHz; for transmitters, we show a power efficiency improvement which exceeds a factor of two over an 5% bandwidth about 20 MHz with an average signal power of 1 W to the radiation resistance.

Method and system for real time control of an active antenna over a distributed antenna system

Abstract: A method and system suitable for supporting various wireless services on a Distributed Antenna System (DAS). The DAS can provide wireless services including voice and data services using the same equipment. The DAS can include one or more active antenna units controlled by an access point, and includes control channels for transferring control and status information between the access point and the antenna. The control channels can be transferred over a separate cable, or transferred using one or more intermediate frequency signals transferred over existing cables. The control channels can be used to configure and control and receive status from the managed components of the DAS including active antennas, control the amplifiers used to process TDD signals, and control the switching of diversity antenna systems.

A Novel Quad-Polarization Agile Patch Antenna

Abstract: In this communication we present a novel polarization-agile microstrip antenna design. To dynamically change the polarization state, the radiating patch is fed by a tunable quasi-lumped coupler. The whole structure can be dynamically altered to radiate electromagnetic waves with vertical linear, horizontal linear, right-handed circular or left-handed circular polarization simply by changing the operating mode of the quasi-lumped coupler. Due to its topology the coupler is simply reconfigured by switching the bias of two varactor diodes via a very simple DC bias circuitry: no additional capacitors or inductors are required. A prototype is fabricated with a 0.762-mm-thick upper layer substrate for the radiating element and a 0.130-mm-thick layer substrate for the coupler circuit, both with the same dielectric material relative permittivity of 2.22. The simulated and measured scattering parameters, the axial ratio in circular radiation-mode and the cross-polarization level in linear mode, the gain and the radiation patterns are presented. The agile polarization capabilities of this new antenna, as demonstrated in this communication, underscore its suitability for modern wireless communications in a multi-path propagation environment.

Fixed-Beam Frequency-Tunable Phase-Reversal Coplanar Stripline Antenna Array

Abstract: A fixed-beam frequency-tunable coplanar stripline (CPS) antenna array using the phase reversal technique and varactor diodes tuning is presented. The antenna array is composed of plurality of half-wavelength CPS sections interconnected by phase reversing crossovers. These crossovers have two functions: they serve as the radiators (small dipoles) of the array and also provide their own required in-phase excitations for broadside radiation. Two microstrip-to-CPS transitions for excitation of the balanced input/output antenna array are implemented and compared. A six-element array is demonstrated theoretically and experimentally, with 9.3 dBi of gain for bidirectional radiation and 12.5 dBi of gain for unidirectional radiation using a back reflector. Moreover, shunt varactor diodes are incorporated along the CPS structure to achieve frequency tuning through a bias voltage control while broadside radiation patterns remain fixed. The return loss and the radiation patterns at several frequencies are presented, and up to 50% tuning range is obtained. The proposed antenna array is simple and uniplanar with small lateral size, high radiation efficiency and high directivity. In addition, it uses a very simple biasing circuit with high DC-RF isolation. Its balanced input/output makes it suitable for RF system integration and active integrated antenna design.

High-efficiency transmission-line GaN HEMT inverse class F power amplifier for active antenna arrays

Abstract: In this paper, a novel load-network solution to implement the transmission-line inverse Class F power amplifier for WCDMA active antenna array applications is presented. The theoretical analysis is based on an analytical derivation of the optimum load-network parameters to control the second and third harmonic at the device output including the device output parasitic shunt capacitance and series inductance. For an inverse Class F power amplifier based on a Nitronex GaN HEMT NPTB00004 with hybrid microstrip implementation, the simulated output power of 37 dBm and power-added efficiency of more than 70% are achieved at a supply voltage of 25 V in a frequency bandwidth of 2.11 to 2.17 GHz. The test board with implemented inverse Class F GaN HEMT power amplifier has been measured and high-performance results with drain efficiencies of about 80% and higher were achieved across the wide ranges of bias supply voltages and operating frequencies.

On the Performance of Trellis Coded Spatial Modulation

Abstract: Trellis coded modulation (TCM) is a well known scheme that applies mapping by set partitioning. The key idea is to group the constellation symbols into sets with each set having the maximum free distance between its symbols. In this paper, a similar approach is applied to antenna constellation points of spatial modulation (SM) in order to enhance its performance in correlated channel conditions. In SM, multiple antennas exist at the transmitter side, but only one of them is active at any par- ticular time instant. The incoming data bits determine the active transmit antenna and the signal constellation point transmitted from it. At the receiver side, the active antenna index and the transmitted symbol are estimated and used together to decode the transmitted information bits. The locations of the transmit antennas are considered as spatial constellation points, and TCM is applied to enhance the bit error ratio (BER) performance of bits encoded into the physical location of an antenna within an antenna array. TCM partitions the entire set of transmit antennas into sub-sets such that the spacing between antennas within a particular sub-set is maximized. The performance of TCSM is analyzed in this paper and compared to the performance of SM and coded V-BLAST (vertical Bell Labs layered space- time) applying optimum sphere decoder algorithm. It is shown that under the same spectral efficiency, TCSM performs nearly the same as SM and V-BLAST in idealistic channel conditions. However, a significant enhancement is reported in the presence of realistic channels performance such as Rician fading and spatial correlation (SC). Index Terms—MIMO, Spatial modulation, Trellis coded modu- lation, V-BLAST, Sphere decoder, Correlated channel conditions, Rician fading, Spatial correlation.

Multiple envelope tracking system for an active antenna array

Abstract: An active antenna array comprises a plurality of transmission paths, a plurality of variable power supply units, and an envelope detection system. The transmission paths are adapted to carry a plurality of similar transmission path signals, and the plurality of transmission paths comprises an amplifier having a power input and a signal input for one of the plurality of similar transmission path signals. The plurality of variable power supply units is connected to the power input of the amplifier for supplying power to the amplifiers. Each of the plurality of variable power supply units comprises an envelope signal input. The envelope detection system is connected to the envelope inputs of the plurality of variable power supply units and adapted to provide a common envelope signal for the plurality of similar transmission path signals to the plurality of variable power supply units. A method for envelope tracking and computer program products for manufacture and method execution are also claimed.

Active Stabilization of Vehicle-Mounted Phased-Array Antennas

Abstract: In this paper, a novel hybrid tracking method for mobile active phased-array antenna systems is developed. The proposed technique consists of a mechanical stabilization loop and a direction-of-arrival (DOA) estimation algorithm, which is based on electronic beamforming. Compared with other tracking methods, the proposed method requires only one low-cost yaw rate sensor. The method utilizes electronic feedback from the phased-array antenna to compensate for the low-cost sensor irregularities. The effectiveness of the proposed tracking method is demonstrated by measured performance of a fast-moving ultra-low-profile phased-array satellite terminal, which uses the proposed approach. The field test results confirm that the hybrid tracking mechanism can nullify the base vehicle yaw disturbances up to 60deg/s and 85deg/s2 and keep the azimuth angle error at less than the permissible bound of [-1deg, +1deg]. Although performance of the proposed tracking system is verified in the context of a mobile satellite television reception system, the basic principles can be applied to any tracking system that employs phased-array antennas. The mobile satellite Internet terminal is an important example.

Analysis of performance of active phased array antennas with distorted plane error

Abstract: The analysis of the degradation of electromagnetic performance of active phased array antennas (APAA) with distorted plane error is an important factor for manufacturing high-performance antennas. To obtain the relation between the plane distortion and electric index to provide significant guidance for the engineer, a coupled structural-electromagnetic model of an APAA is developed, which describes the effect on the performance of the distorted plane error caused by the bent and bowl shape distortion in the radiated element position. The application of the model to a planar APAA demonstrates the degradation of the sidelobe level and gain of antenna with different distortion grades. The satisfactory results provide a theoretical guidance for the engineer to determine the structural tolerance.

Accurate Antenna Pattern Modeling for Phased Array Antennas in SAR Applications—Demonstration on TerraSAR-X

Abstract: The high flexibility and tight accuracy requirements of today's spaceborne synthetic aperture radar (SAR) systems require innovative technologies to calibrate and process the SAR images. To perform accurate pattern correction during SAR processing, an Antenna Model is used to derive the multitude of different antenna beams generated by active antenna steering. The application of such an Antenna Model could be successfully demonstrated for the TerraSAR-X mission, launched in 2007. The methodology and the results of the inorbit verification with an achieved accuracy of better than ± 0 . 2 dB is reviewed in this paper in detail showing its outstanding accuracy.

Active antenna, base station, method for refreshing amplitudes and phases, and method for processing signals

Abstract: An active antenna, a base station, a method for refreshing the amplitude and phase, and a signal processing method are disclosed to simplify the structure of a phase shifter and guarantee the reliability of the phase shifter. The active antenna or the base station includes an antenna dipole array, a transceiver array, a digital processing unit (DPU), and a transceiving calibration unit. During signal reception, the transceiver demodulates a radio frequency (RF) signal of the antenna dipole into an IQ analog signal, and outputs the IQ analog signal to the DPU; the DPU converts the demodulated IQ analog signal into an IQ digital signal, and performs digital beam forming (DBF) on the IQ digital signal according to the transceiving calibration unit; during signal transmission, the transceiver modulates the IQ analog signal of the DPU into an RF signal, and outputs the RF signal to the antenna dipole; the DPU converts a signal of a base band unit (BBU) into an IQ digital signal in serial/parallel (S/P) mode, and performs DBF on the IQ digital signal according to the transceiving calibration unit.

Active antenna array with multiple amplifiers for a mobile communications network and method of providing DC voltage to at least one processing element

Abstract: The present disclosure teaches an active antenna array for a mobile communications network. The active antenna array comprises a plurality of antenna elements, a first port, a first DC voltage supply and at least one DC voltage extractor. The plurality of antenna elements relays at least first protocol radio signals. The first port is connected to at least one individual first protocol relay path. The first port relays a general first protocol receive signal to a first protocol link. The first DC voltage supply provides a first DC voltage to at least a portion of the first protocol link. The at least one DC voltage extractor, is located in the at least one individual first protocol relay path. The DC voltage extractor extracts at least one individual DC voltage to supply an at least one amplifier.

Active Reflectors: Possible Solutions Based on Reflectarrays and Fresnel Reflectors

Abstract: An overview about some of the recent Spanish developments on active reflectors is presented. In the first part, a novel beamsteering active reflectarray is deeply studied. It is based on implementing in each elementary radiator an IQ modulator structure, in which amplitude and phase control of the scattered field is achieved. Finally, a special effort is made in offering solutions to overcome the active antenna integration problems. In the second part, the active concept is firstly extended to Fresnel reflectors. Thanks to the development of a proper simulator, this special structure can be easily analysed. This simulator allows the study of performance of this kind of reflectors and, applying evolutionary algorithms, to find optimal configurations of reflector in accordance with the given specifications for the conformal radiation pattern.

Dual port ASA for frequency switchable active antenna

Abstract: This report presents the design of a dual-port dual-band annular slot antenna suitable for use in the feed-back path of an oscillator resulting in an active antenna configuration. The proposed antenna is designed to radiate and transmit equal amounts of power. The return loss of the proposed antenna is higher than that desired for one-port antenna application at the desired dual-band frequencies. The antenna is fabricated on one side of a Neltec substrate (e r =3.2 and thickness = 0.762 mm) and the microstrip feeding line is fabricated on the opposite side of the board. The antenna was designed to operate at WLAN bands centered at 2.4 and 5.2 GHz. The simulated and measured results show fairly good agreement. The measured return losses were found 20.5 dB at 2.4 GHz and 13.9 dB at 5.2GHz while simulated return losses were 9.36 dB at 2.4 GHz and 31.35 dB at 5.2 GHz. The radiation pattern is approximately omnidirectional at both frequencies in H-plane.

Active scan-beam reflectarray antenna loaded with tunable capacitor

Abstract: In this paper, the design concept of an active reconfigurable reflectarray antenna has been proposed and tested. The elementary radiators are hollow patch antennas loaded with varactor-diode device which its reflected phase can be varied. This phase alteration is based on the variation of the diode capacitance which can be achieved by varying the biasing voltage of the active varactor device. By activating these varactor devices, the phase of each antenna element in the array configuration can be adopted dynamically and consequently its radiation beam can be reconfigured. The advantage above the MEMS switches is complexity of the integration and continues beam scanning capability. The reflectarray incorporating active elements has been built and tested at 6.0GHz. The performance of the proposed active antenna is excellent which pioneers design of arbitrarily reconfigurable antennas.

Dipole array with reflector and integrated electronics

Abstract: A dipole antenna array comprising a ground plane, at least one dipole antenna including an active antenna element and a grounded antenna element, at least one reflector and integrated electronics, wherein the active antenna element is isolated from the ground plane and extends substantially perpendicular to the ground plane and the grounded antenna element extends in a direction substantially opposite to the active antenna element, the ground plane is contained within the area bounded by the reflector; the integrated electronics include at least one of a signal down converter and a signal up-converter, and at least some of the integrated electronics are contained in a space defined by at least one of a portion of the ground plane and a portion of the reflector.

Ku Band Hemispherical Fully Electronic Antenna for Aircraft in Flight Entertainment

Abstract: The results obtained in the frame of the ESA activity “Advanced Antenna Concepts For Aircraft In Flight Entertainment” are presented. The aim of the activity consists in designing an active antenna able to guarantee the Ku band link between an aircraft and a geostationary satellite in order to provide in flight entertainment services. The transmit-receive antenna generates a single narrow beam to be steered electronically in a half sphere remaining compliant with respect to stringent requirements in terms of pattern shape, polarization alignment, EIRP, G/T, and using customized electronic devices. At the same time, the proposed solution should be competitive in terms of cost and complexity.

Active antenna, base station, method for updating amplitude and phase and method for signal processing

Abstract: Implementations of the present invention disclose an active antenna, a base station, a method for updating amplitude, phase and delay and a method for signal processing, in order to solve the problem that phase-shifting network has complex structure and is unreliable. Said active antenna or base station includes an antenna element array, a transceiver unit array, a digital processing unit and a transceiver adjusting unit. When receiving signal, the transceiver unit carries out down conversion demodulation for radio frequency signal from antenna element to produce IQ analog signal, which is outputted to said digital processing unit, and the digital processing unit converts the down conversion demodulated IQ analog signal into IQ digital signal, and carries out digital beam forming for the IQ digital signal based on transceiver adjusting unit; When transmitting signal, the transceiver unit carries out up conversion modulation for IQ analog signal from digital processing unit to produce radio frequency signal, which is outputted to antenna element, and the digital processing unit carries out serial/parallel conversion for the signal from base band unit to produce IQ digital signal, and carries out digital beam forming for the IQ digital signal based on the transceiver adjusting unit.

Calibration method and active antenna

Abstract: A calibration method and an active antenna are provided. The active antenna includes K antenna dipole arrays, 1st to Kth transceiver unit arrays corresponding to the antenna dipole arrays, 1st to Kth calibrators, a feature difference calculating unit, and baseband processing modules. The 1st to Kth calibrators are configured to obtain P feature difference values between P calibration signals passing through all calibration loops of the active antenna and an original calibration signal. The feature difference calculating unit is configured to calculate a feature difference value of a receiving channel and/or transmitting channel of each transceiver unit relative to a reference receiving channel and/or transmitting channel respectively. Each baseband processing module is configured to perform feature compensation on a service signal of the corresponding transceiver unit in a digital domain. Therefore, feature differences between all transceivers respectively disposed on a plurality of boards of the transceiver arrays can be calculated, so as to realize accurate calibration on transceiver arrays when the transceiver arrays are distributed on a plurality of boards.

Antenna diversity system using active antenna

Abstract: An antenna diversity system using an active antenna is disclosed. The disclosed system includes a first antenna used to receive and send the signal of a first frequency band; a second antenna used to receive and send the signal of a second frequency band; and an active circuit part that is implemented by active elements, wherein in the first mode said second antenna operates as a passive antenna, and in the second mode said second antenna connects with said active circuit part electrically and operates as an active antenna. The disclosed diversity system is advantageous in that it enables a diversity antenna to be utilized without increasing the size of the antenna and also enables the use of an active antenna as a diversity antenna.

Active antenna array for a mobile communications network with multiple amplifiers using separate polarisations for transmission and a combination of polarisations for reception of separate protocol signals

Abstract: The present disclosure teaches an active antenna array for a mobile communications network. The active antenna array comprises a plurality of first polarization antenna elements and a plurality of second polarization antenna elements. The plurality of first polarization antenna elements is connected to a first protocol signal generator. The plurality of first polarization antenna elements are adapted to radiate an individual first protocol transmit signal. An individual one of the plurality of second polarization antenna element is connected to an individual one of a plurality of second protocol signal generators. The plurality of second polarization antenna elements is adapted to radiate an individual second protocol transmit signal. An individual one of the plurality of first polarization antenna elements and the individual one of the plurality of second polarization antenna elements are adapted to receive both, an individual first protocol receive signal and an individual second protocol receive signal.

Front-end circuit for improved antenna performance

Abstract: Means for reducing detrimental interactions between an active antenna and an inactive antenna are disclosed. The reduction is achieved by providing a preferred termination state of the inactive antenna.

270°C, 1 GHz oscillator-type active antenna

Abstract: Reported is the first demonstration of an active antenna operating at 1 GHz and at temperatures above 200degC. A Clapp oscillator integrated with a slot-ring antenna generated and transmitted a 1 GHz signal from 25 to 270degC. The oscillation frequency varied by less than 4 over the temperature range.

A 2.4-GHz Wireless-Over-Fibre System Using Photonic Active Integrated Antennas (PhAIAs) and Lossless Matching Circuits

Abstract: This paper demonstrates that very low cost wireless-over-fibre systems can be implemented without RF amplification by using lossless matching techniques. Single stub matching circuits were designed on low loss substrates and integrated with photodiode chips and results show that the link gain can be theoretically improved by more than 8 dB. A 2-port link gain model is developed using Agilent ADS which allows simple wideband modeling of such systems. Finally the system is tested using a ldquoliverdquo access point both with and without matching and results show that a maximum RF range of 4 m can be obtained at 2 Mbps data rate over 317 m of installed MMF with no RF amplification.

Array antenna apparatus including multiple steerable antennas and capable of eliminating influence of surrounding metal components

Abstract: An antenna unit is provided with: steerable antennas, each having one active antenna element and two parasitic antenna element; and metal blocks. Each of the active antenna elements is associated with at least one of the metal blocks such that the metal block is disposed remote from the active antenna element by a predetermined distance and operates as a reflector for the active antenna element. Each of the parasitic antenna elements is provided with a switching circuit for changing an electrical length of the parasitic antenna element, and the parasitic antenna element operates as a reflector for an active antenna element of the same steerable antenna as the parasitic antenna element by changing the electrical length using the switching circuit.

An Active High Impedance Surface for Low Profile Tunable and Steerable Antennas

Abstract: In this letter, an approach for designing a tunable and steerable antenna is presented. The antenna model is based on a wideband bow-tie radiating element mounted above an active Artificial Magnetic Conductor (AMC). The AMC geometry consists of a Frequency Selective Surface (FSS) printed on a thin grounded dielectric slab in which some chip-set varactor diodes are placed between the metallic elements and the backing plane through vias. The resulting antenna can be tuned over the S-Band by simply changing all varactor capacitances through an appropriate biasing voltage. Moreover, this structure can operate a beam scanning over each working frequency by applying an appropriate biasing voltage to the active elements of the AMC surface in accordance to leaky radiation principles. The low profile active antenna is characterized by an overall thickness of 5.32 mm, which corresponds to approximately lambda/24 at the centre of the operating band.

Double-mode time service active antenna

Abstract: The invention relates to a double-mode time service active antenna which comprises a ceramic dielectric antenna, a low-noise amplifier unit, an anti-lightning, -surge and -impact circuit, a power supply voltage stabilizing circuit, an N-type pin electric connector, a double-sided printed copper-clad plate with a microstrip circuit and an antenna shell, and is characterized in that the ceramic dielectric antenna, the low-noise amplifier unit, the anti-lightning, -surge and -impact circuit and the power supply voltage stabilizing circuit are subsequently connected through a microstrip connection line on the double-sided printed copper-clad plate to form a circuit module of the double-mode time service active antenna; a double-star radio frequency signal output by the amplifier unit is connected with the N-type pin electric connector through a coaxial cable; an N-type radio frequency output end of the pin electric connector is arranged on a pre-reserved hole of the shell; and the double-mode time service active antenna realizes the function of receiving GPS and 'Dipper II' time service signals through optimized design, thereby not only improving the time service reliability and flexibility of a base station, but also reducing the equipment manufacturing cost

Reconfigurable scan‐beam hollow patch reflectarray antenna loaded with tunable capacitor

Abstract: In this article, the design concept of an active reconfigurable reflectarray antenna has been proposed and tested. The elementary radiators are hollow patch element loaded with varactor-diode device in which the reflected phase can be varied. This phase alteration is based on the variation of the diode capacitance which can be achieved by varying the biasing voltage of the active varactor device. By activating these varactor devices, the phase of each antenna element in the array configuration can be adopted dynamically, and consequently, its radiation beam direction can be reconfigured. The advantage of the MEMS switches is the complexity of the integration and continuing beam scanning capability. The reflectarray incorporating active elements has been built and tested at 6.0 GHz. Narrow band multifrequency shared aperture is demonstrated theoretically and experimentally. The performance of the proposed active antenna is excellent, which pioneers the design of arbitrarily reconfigurable antennas. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 367–374, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24050

Modular active antenna for receiving multiple broadcasting signals

Abstract: The present invention relates to a modular active antenna for receiving multiple broadcast signals. The modular active antenna includes an internal antenna, an active module and a printed circuit board. The internal antenna is formed in a polyhedral shape having an open bottom surface and configured to receive multiple broadcast frequency signals. The active module is arranged below the internal antenna to constitute a single module together with the internal antenna and is configured to selectively perform impedance matching on any one of the multiple broadcast frequency signals received by the internal antenna. The printed circuit board is configured to allow the internal antenna and the active module to be mounted thereon and is provided with a ground surface formed on the bottom thereof. Therefore, the present invention is advantageous in that it can receive multiple broadcast frequency signals through a single active antenna.

Flex-rigid architecture for active millimeter-wave antenna arrays

Abstract: A flex-rigid assembly is proposed for densely packed active antenna arrays. The multilayer compound bases on Liquid Crystal Polymer (LCP) and common RF substrates. The integration of the RF components as well as thermal and mechanical aspects are addressed. A complete 4×4 Ka-Band array providing polarization multiplex is demonstrated. Far-field measurements of the antenna elements are discussed.