Showing papers on "Active antenna published in 2001"

Integrated active antenna for multi-carrier applications

Abstract: A distributed antenna array comprising a plurality of antenna elements, and a plurality of power amplifiers, each power amplifier being operatively coupled with one of said antenna elements and mounted closely adjacent to the associated antenna element, such that no appreciable power loss occurs between the power amplifier and the associated antenna element, each said power amplifier comprising a relatively low power, linear power amplifier.

Pro-active antenna switching based on relative power

Abstract: A system and a method for switching antenna fields without waiting until data packets containing errors are detected. This is accomplished by monitoring the signal power for each antenna field immediately after receipt of data packets via the currently active antenna field and then switching to another antenna field having greater signal power. A communications channel is provided which has a capacity greater than that required by the data to be transmitted. This extra capacity is used to introduce time periods when no data is being transmitted. During these time periods, known bit patterns are transmitted, and the signal power during receipt of each of these blank packets is estimated for each antenna field. The receiver then switches to the most appropriate antenna field based on highest signal power (e.g., based on a weighted average for the N-th most recent sample periods) and continues to receive the transmitted data without interruption.

Symmetrical antenna structure and a method for its manufacture as well as an expansion card applying the antenna structure

Abstract: An antenna structure which comprises at least one active and at least one parasitic antenna conductor and which is arranged to be fitted on top of a planar electroconductive surface at a distance from said surface which is arranged to be used as a ground plane for said antenna structure, and which antenna structure comprises, arranged parallelly at a distance from each other, a first antenna conductor and a second antenna conductor which have an electrical length of approximately ¼ of the wavelength of the used frequency and which are parallel with said ground plane, and which comprise opposite first ends and opposite free second ends, wherein the antenna structure is equipped with symmetrical conductors for short-circuiting the first ends to said ground plane and a first conductor for coupling the supply to a desired point between the first end and a second end of the active antenna conductor. The antenna structure is symmetrically equipped with also a second conductor for coupling a short circuit to the corresponding point between the first end and the second end of the parasitic antenna conductor in such a way that in the rotated position of 180° of the antenna structure, the second conductor is, in turn, used as said supply and the first conductor is, in turn, used as said short circuit.

Vision-based active sensor using a flexible beam

Abstract: Proposes a vision-based active sensing system, termed vision-based active antenna. This is composed of a camera, a flexible beam whose force-deformation characteristic is known, and an actuator for rotating the beam. The camera observes the beam deformation, including the contact information, while the beam is in contact with an object. By solving a set of equations based on the information acquired through the camera, the sensor can detect the contact location, the contact force, and the stiffness of the object, even though the contact point is hidden by occlusion. For two particular versions, we show some experimental results to verify the basic idea.

Scanning, circularly polarized varied impedance transmission line antenna

Abstract: The present invention features a cross-element, steerable, scanning meander line loaded (MLA) antenna with circular polarization. The transmission lines comprise a plurality of alternating or stepped impedance sections with the high impedance elements acting as active antenna elements. The impedance varies depending upon the spacing from the moveable ground plane. The orthogonal MLA elements allow the application of an in-phase and a 90° shifted signal, thus each linear array radiates a circularly polarized RF signal. Controlling the spacing between the ground plane and transmission line provides relative phase control between the active elements and thereby phased-array directional control of the antenna. Forming a two-dimensional array of these linear arrays, produces a compact, low-cost, scanning, phased-array antenna.

Transceiver system of an active antenna

Abstract: The transmission/reception system has a number of transmission/reception modules (1) each having a transmission channel (3) and a reception channel (2). Each transmission/reception module has at least one local oscillator (17), using a common central reference frequency of between 5 and 500 MHz, which is coupled directly to the mixer stage (8) of the transmission channel and/or reception channel.

Zero-IF detection active antenna

Abstract: A zero-IF receiver is implemented based on the active antenna design. The active devices, Schottky diodes, are compactly integrated with two patch antenna elements to act as the mixers. The active antenna can perform both direct-conversion demodulation and direction finding.

Single feed, multi-element antenna

Abstract: An array antenna (200) capable of use with a single signal feed has a transmission line oriented substantially parallel to a ground plane (220), which transmission line has a multiplicity of sequential sections with each sequential section having a different spacing from the ground plane (220) than each of its immediately adjacent sequential section. This stepped or varied impedance transmission line forms an array in which the sections spaced further from the ground plane (220) become active antenna elements. Controlling an electrical spacing between the ground plane (220) and transmission line provides relative phase control between the active elements and thereby phased-array directional control of the antenna.

Radically new design of SAR satellite: short vertical antenna approach

Abstract: The idea of this work is the use of a vertical antenna (antenna placed in the orbit plane) for a spaceborne radar. This surprising geometry is proven to work properly and to simplify the design of the instrument, particularly when it is associated with a short antenna length (<5 m, along speed vector). The number of antenna control points is greatly reduced, which saves cost and mass of an active antenna. A single pencil beam allows all the incidences and modes to be achieved. Viewing on both sides of the satellite track is enabled. Spotlight mode is no longer needed and therefore most of the operational constraints attached to high resolution are removed. Merits of the geometry are not limited to the instrument, a cascade of other innovations converges into a radically new design of the whole satellite for an ultimate goal of simplification and cost reduction, this is radar SAIL concept. The merits and cost savings of short vertical antenna are illustrated with a 1 m resolution X band mission, and the extra merits of the integrated SAIL architecture with respect to the standard satellite architecture are discussed.

Active antenna using multi-layer ceramic-polyimide substrates for wireless communication systems

Abstract: This paper proposes an active antenna structure for high-speed wireless communication systems that is constructed with multi-layer alumina-ceramic and polyimide substrates. This antenna structure incorporates a transmitter/receiver amplifier and time division duplex switch circuits that are mounted on a Monolithic Microwave Integrated Circuit (MMIC) chip and a low-pass filter circuit. A prototype active antenna at 25 GHz is presented and the measured total gain for both transmission and reception of more than 21 dB is achieved with the directional gain of approximately 11 dBi.

Method and apparatus for using RF-activated MEMS switching element

Abstract: The present invention features an RF-actuated microelectromechanical systems (MEMS) switch for use with switchable RF structures such as antennas. An antenna within each MEMS switch module is coupled to a tuned circuit and a detector. The DC voltage output of the detector is used as the control input to the MEMS switch. This allows arrays of MEMS switch modules to be actuated by remotely generated radio frequency signals thus alleviating the need for running metallic conductors or optical fibers to each MEMS switch. The MEMS switch is particularly suited for use in conjunction with both passive and active antenna elements to allow reconfiguration of antenna or other RF structures. Frequency response characteristics, phasing, and directionality characteristics may be altered easily.

Ring-coupled-oscillator sequentially rotated active antenna

Abstract: In this paper, an active four-element patch antenna, backed by four GaAs monolithic-microwave integrated-circuit (MMIC) 4.4-GHz oscillators, self-locked by mutual coupling through a lumped capacitive ring MMIC network, has been designed, fabricated, and tested. The sequentially rotated arrangement given here when augmented with a lumped capacitive coupling network suggests that in-phase oscillator entrainment is guaranteed so that spatial power combination by the antenna array occurs with circular polarization characteristics.

Point-actuated aperture antenna development

Abstract: Consistent changes in both commercial and military satellite needs have created the need for antennas with additional flexibility. Military surveillance may require the ability to focus the radiation pattern to increase the bandwidth or resolution in a certain area. Commercial satellites may need to change coverage area to meet evolving consumer needs or to compensate for adverse weather or atmospheric conditions. Recent studies on active antennas have shown that the far field radiation pattern can be changed by altering the shape of the sub reflector. In this research, we control the antenna far field radiation pattern by controlling the shape of the sub reflector using numerous point actuators placed perpendicular to the reflector surface. The PZT stack coupled with a stick-slip mechanism give the point actuators used in this design an advantage over similar studies using PZT bimorph or PVDF actuators to generate the actuation force in that the displacement can be maintained without the continuous application of voltage. An electromechanical model is used to describe the motion of the stack, and the stick slip mechanism is modeled similar to power screw-type actuators. A combined finite element/electromagnetic analysis code is used to determine the desired shape of the reflector, and the corresponding actuator displacements. The final shape of the reflector is verified using stereo photogrammetry.

Time reversal through a solid–liquid interface and super‐resolution

Abstract: Time‐reversal can be used to refocus optimally a signal back onto the source that emitted it. An active array antenna is used to record the wave as a function of time and then, the recorded field is time reversed and retransmitted. The time reversed wave backpropagates through the medium and refocuses approximately on the initial source position. From the experimental point of view, time‐reversal devices are designed to work primarily in a fluid environment. However, time reversal refocusing can be realized also in solids. To do so, the solid is surrounded by a fluid in which the active antenna is located. We propose a numerical formulation describing the time reversal phenomenon through a fluid–solid interface and we analyze with numerical simulations the refocusing resolution obtained in homogeneous media. We also show numerically that multipathing caused by random inhomogeneities improves the focusing of the back‐propagated elastic waves beyond the diffraction limit. This phenomenon is called super‐resolution and was seen previously in acoustic wave propagation.

Dual disk active antenna

Abstract: An antenna that can be used as an active receiving antenna and a transmitting antenna is formed by forming dual disk antenna elements. The dual disk antenna elements are formed by etching a pattern in a layer of conducting material, such as copper, formed on a substrate of dielectric material. One of the disks acts as the active antenna element and the other disk acts as a counterpoise antenna element. In one embodiment a RF amplifier chip is used to form an active receiving antenna. In another embodiment the RF amplifier chip is removed and the antenna can be used either as a receiving antenna or a transmitting antenna. In another embodiment a RF amplifier chip is used with an electronic switch to include the RF amplifier chip when the antenna is used as a receiving antenna and to switch the RF chip out of the circuit when the antenna is used as a transmitting antenna.

Active antenna apparatus of satelite portable phone

Abstract: PURPOSE: An antenna device for satellite mobile communication terminal is provided to improve a noise index due to a signal receiving process by mounting a signal process unit for example a duplexer, a low noise amplifier and the like on an additional print circuit board. CONSTITUTION: A duplexer divides a transmission path of a signal transmitted/received through an antenna(230). A low noise amplifier decreases a noise ratio of the received signal and selects an appointed band. A print circuit board(225) exchanges the signal with a main body(200) of a mobile communication terminal and supplies the main body(200) of the mobile communication terminal with an operation power through an antenna cable(226).

Radio masking device

Abstract: radio engineering; information protection against unauthorized access. SUBSTANCE: device used for masking information of computer-aided control systems and electronic computers (receiving stray electromagnetic beams and pickups) by generating noise signal and effectively radiating this signal within entire band of frequencies being masked has noise generator and active antenna circuit in the form of two coupled oscillators one being inertial self-bias delayed-feedback oscillator and other, adjustable-delayed-feedback oscillator. Input of first oscillator connected to output of low-frequency noise source functions as noise-generator input and output of second oscillator loaded into transmitting antenna of magnetic-dipole type, as noise-generator output. One end of magnetic dipole is connected to generator output and other one, to common bus. EFFECT: improved operating stability of device. 2 cl, 4 dwg

Recent developments in RF front ends based upon active antenna concepts

Abstract: Several developments in RF front end technology based upon the active antenna concept are presented. RF front ends utilizing active antenna concepts have shown improvements in such areas as power added efficiency, compactness, low noise figure, and increased functionality. These improvements are illustrated with a Class F power amplifier transmitter with an integrated circular patch antenna, a circularly polarized patch antenna with integrated LNAs, a 60 GHz quasi-optics self oscillating mixer, and two designs implementing the recently developed broadband quasi-Yagi antenna.

Active antennas incorporating tunnel diodes-large signal model approach

Abstract: In this letter, a comprehensive dc and RF model of heterostructure interband tunnel diodes (HITDs) is extracted. Active antennas incorporating tunnel diodes are analyzed in the time domain using this tunnel diode model. The simulated and measured results are in good agreement in terms of oscillation frequencies of the active antennas. Phase noise of -114.67 dBc/Hz @1.0 MHz offset is achieved for injection-locked active antennas. The simulated injection locking range of a Ka band active antenna array is investigated.

Electronically steerable high frequency active antenna having elementary cells each having half phase shifts and having parallel diode switching with outer perpendicular conductor zones.

Abstract: The active reflector receives electromagnetic radiation in a given direction The antenna is made up of elementary cells with phase shifters (31) in a conductor plane Each phase shifter has two half phase shifters (50) with conductor diodes (42) across the two halves, providing two states The conductors are normal to two conductor zones (49)

Integrated Active Antenna Noise Figure Characterization Using a Cryogenic Anechoic Noise Source

Abstract: For the phased array concept of the next generation radio telescopes, the Square Kilometre Array (SKA), a large number of broadband, low noise amplifiers are necessary. The envisaged array antennas for SKA are printed circuit type antennas (Vivaldy, bunny ear) Smolders (1), which should be integrated with the first amplifier stages. To enable optimum performance over a decade bandwidth it is advantageous to directly match the antenna impedance to the required impedances for low noise matching and maximum power transfer of the active device, without an intermediate matching step to 50 ohm as is common for most microwave and RF systems. This paper describes the design, but more importantly the characterization, of the integrated active antenna. An accurate characterization of e.g. noise figure cannot be executed with standard equipment due to the non-50 ohm intermediate impedance levels. To overcome this problem, a hot/cold noise figure measurements has been developed for the complete active antenna.

K-band spatial combiner using finline arrays in oversized rectangular waveguide

Abstract: This paper presents the K-band spatial combining system based on the tapered-slot antenna arrays integrated in an oversized rectangular waveguide. The active antenna cards were designed and built monolithically, and a preliminary result of a 2/spl times/4 system has been presented in this paper.

Active phased array antenna, two-dimensional planar active phased array antenna, and transmitter and receiver

Abstract: PROBLEM TO BE SOLVED: To solve the conventional problem of an active phased array antenna unable to have a heat dissipating structure that is thin and light in weight, when using a high-output power amplifier which releases a large amount of heat. SOLUTION: An active device 9-6 and an excitation antenna element 9-1 are formed into an excitation active antenna 9 of integral structure, the excitation active antenna 9 is disposed on a metal plate 7, and the metal plate 7 has a structure, formed of hollow pipes which are joined together in parallel crosses. A coupling antenna plate 4, on which coupling antenna elements 3 are formed, is arranged above the excitation active antenna 9, and a radiation antenna plate 2, on which radiation antenna elements 1 are formed, is arranged above the coupling antenna plate 4, so that a power is fed to the radiation antenna elements 1 from the coupling antenna elements 3 by stabling electromagnetic coupling.

Analysis and design of active antenna arrays

Abstract: In this paper, the FDTD method is extended successfully to analyze active antennas using Z-transform method for small signal model and by a stable scheme for large signal model. The two approaches are validated by comparison with analytical impedance expression in frequency domain. Through these approaches, we analyze active antennas and antenna arrays containing tunnel diodes. Effects of various device parameters are investigated in order to find desired oscillations. Single and array active antennas are designed and tested. Experimental and simulated results are given and compared.

Low noise integrated active antenna as image reject mixer (IRM)

Abstract: A patch antenna integrated with two Low Noise Amplifiers (LNA) is implemented to act as an Image Reject Mixer (IRM). The low noise active antenna system transforms a received radio frequency signal into two signals, which are out-of phase to each other. The image signals can be cancelled by the IRM. The antenna, LNA's, mixers and local oscillator (LO) are integrated into a single Active Integrated Antenna (AIA) module. An external IF 90/spl deg/ hybrid coupler is required in the IRM. The advantages of the LNA active antenna mixer system are low noise, image signal rejection, low cost and simple circuitry of front-end, and improved receiver sensitivity.

Design of a spherical array self-mixing oscillator antenna

Abstract: Principle of a spherical array self-mixing oscillator antenna is discussed in this paper. Applying the injection locking technique to the spherical array, in which elements are made of simple waveguide radiators, beam steering with constant pattern in different directions can be achieved without using the sophisticated phase shifters. This antenna is designed and tested at a frequency of 10 GHz.

Global Design of an Active Integrated Antenna for Millimeter Wave

Abstract: An active integrated antenna working in the millimeter wave has been realized in a monolithic process. The concept of active integrated antenna is first introduced, then the design of the integrated circuit based on a global approach, following electromagnetic and circuit simulations, is presented. The obtained performances of the active antenna are discussed and compared to a passive one.

Three-component wide-band low-frequency magnetic antenna for diagnostics of magnetic fields in outboard space

Abstract: A three-component wide-band low-frequency magnetic antenna for diagnostics of magnetic fields in outboard space is considered. Methods of calculation of such antennas parameters and technical means for fulfilling the required characteristics are described. The basic technical, structural and exploitation characteristics of the MP-3M three-component on-board active antenna are given.