Showing papers on "Active antenna published in 1992"

Directional scanning circular phased array antenna

Abstract: A directional scanning antenna includes a circular array of a plurality of antenna elements extending several wavelengths in diameter. The number of antenna elements are sufficient to form a plurality of directionally-oriented subsets of active antenna elements and associated subsets of parasitic antenna elements. An antenna feed system provides connections to each one of the plurality of antenna elements that include connections to electronically variable reactances and connections to a source or receiver of electromagnetic energy. The antenna feed system is controllable to provide connections between the subsets of active antenna elements providing wave propagation and reception in one or more directions and to provide connections between a plurality of the remainder of antenna elements in associated subsets of parasitic antenna elements to assist the directionality of the antennas.

Compact amplifier integration in square patch antenna

Abstract: A packaged microwave bipolar transistor has been integrated directly onto a rectangular microstrip patch to obtain extra power gain and to reduce power losses. The radiating element geometry has been modified to incorporate the active devices. This active antenna uses a small number of components and takes the same place as a passive antenna. An extra gain of 8dB is obtain at 1.68 GHz.

Dual-device active patch antenna with improved radiation characteristics

Abstract: An active microstrip patch antenna for quasioptical power-combining arrays is described. The oscillator circuit uses two Gunn diodes which symmetrically load a resonant patch. The symmetry of the structure and the push-pull operation of the devices results in a dramatic decrease in H-plane cross-polarisation, improved copolarisation patterns, and twice as much power as a single-device patch.

Layered parallel interface for an active antenna array

Abstract: A transmit/receive layer is provided adjacent to an array of antenna elements. The transmit/receive layer has an array of transmit receive modules, each module associated with one of the antenna elements. An analog to digital converter and a digital to optical converter of one of the modules couple an RF signal from the associated antenna element to optical fibers. An optical to RF converter in each of the modules converts an amplitude modulated optical transmit signal from an optical fiber to an RF transmit signal for transmission by the associated antenna element. Frequency down and up converters can be added to perform super heterodyne frequency conversion based on a reference frequency control signal transmitted over the optical fibers. At the ends of the optical fibers opposite to the transmit/receive layer, a receive layer, a transmit layer, transmit and receive beamforming layers, dedicated signal synthesizer, control signals, and amplitude modulated optical diode lasers and photodiodes are provided. The transmit layer provides an array of amplitude modulated laser diodes, each associated with one of the antenna elements. The receive layer provides an array of receive optical to digital converters coupled to the optical fibers. A matrix of switches selects appropriate signals from the M×N array of parallel receiving beams for subsequent radar target surveillance, tracking, and identification processing.

Satellite antenna system

Abstract: The invention relates to a satellite antenna system particularly for land mobile voice communication, comprising a radiator unit (1') which is steerable to the satellite in the azimuth plane. According to the invention, the satellite antenna system includes a number of antenna elements (1; 1¹ - 1¹²), of which the radiator unit (1') is formed, a control unit (4) and a switching unit (5); the antenna elements of the said radiator unit are adjacently arranged and evenly spaced in a circular configuration, and of these antenna elements, two adjacent elements belong simultaneously to one and the same active antenna unit (6), and the said two elements are chosen by means of the control unit and the switching unit to receive circularly polarized electromagnetic radiation from a desired direction, and to transmit the same to essentially the same direction.

Self-detection performance of active microstrip antenna

Abstract: Experimental results are presented for the (S + N)/N ratio of an active microstrip antenna operated as a selfoscillating detector. The antenna element uses a GaAs MESFET as the active device and is biased from a single sided DC supply (Vdc = 3.77V, 1dc = 65mA). The element oscillates at 10.03GHz and produces approximately 4mW of radiated power. It is shown that the (S + N)/N ratio produced by the active element when operated as a selfoscillating detector varies nonlinearly between 6dB/30Hz and 60dB/30Hz for synthetically generated Doppler frequencies between 500 Hz and 20 kHz, respectively. The effect of bias voltage control on selfdetector performance is illustrated for a Doppler frequency of 1 kHz.

Novel FET active patch antenna

Abstract: A novel dual-FET active patch antenna element for quasi-optical power combining arrays is described The circuit uses two FETs which symmetrically load a split patch antenna The push-pull operation of the devices decreases H-plane crosspolarisation dramatically A power output of 47 mW was achieved at 81 GHz

Planar dielectric resonator stabilized HEMT oscillator integrated with CPW/aperture coupled patch antenna

Abstract: A novel design of an active antenna with a dielectric resonator stabilized HEMT (high electron mobility transistor) oscillator (DRO) and an aperture-coupled patch antenna is reported. The circuit is fabricated using a coplanar waveguide (CPW) with the oscillator and the antenna on opposite sides of the substrate. The active antenna was demonstrated at 7.6 GHz; however, the design can be scaled to higher frequencies. Excellent oscillator characteristics and radiation patterns have been obtained. >

An active offset antenna having two reflectors

Abstract: Active antenna of "offset" type having two reflectors (3, 4) in a periscope configuration. A radioelectric lens (5) is provided at the foci (F, F') of the two reflectors (3, 4). It is composed of a collector (6), and of a primary array (7) of much larger size than the collector. The "small" sources of the collector (6) correspond one-to-one and in a geographically identical manner with the "large" sources of the primary array (7) to which they are respectively linked by way of devices for fine adjustment of phase.

New FET active notch antenna

Abstract: A new design for an active antenna in which an FET oscillator is integrated with a notch antenna has been demonstrated The structure radiates 89mW of power at a frequency of 698GHz The FET active notch antenna is suitable for use as a low cost transmitter or in quasioptical power combining arrays

Two-port active coupled microstrip antenna

Abstract: A multilayer structure, based on a patch antenna coupled through a nonresonant slot to a pair of feeding microstrips is a versatile module which can be used as a radiating and resonating element in a number of different configurations. Direct connection to a low cost transistor in a feedback loop results in a very simple active antenna, as reported in the Letter. Different termination conditions at the four microstrip ports give rise to a number of alternative configurations for active generation/detection and multipatch arrays.

A Ka-band cavity-enclosed aperture-coupled circular patch antenna and array for millimeter-wave circuit integration

Abstract: A cavity-enclosed aperture-coupled circular patch antenna was used at 29.3 GHz for integration in microwave integrated circuits and monolithic microwave integrated circuits. The design addresses heat dissipation in active antenna applications, surface wave suppression in large phased arrays, isolation between antenna and circuit, increased impedance bandwidth, and reduced back radiation. A prototype 4*4 array demonstrated low mutual coupling between adjacent elements in a worst-case environment. This conformal antenna, should prove useful in many radar, communication, and remote sensing applications. >

Two-dimensional optical architecture for phase and time-delay beam forming in a phased-array antenna

Abstract: We propose and experimentally demonstrate a two-dimensional optical architecture, based on polarization switching by N spatial light modulators of p x p pixels, which provides 2 exp N-1 time delays values and an analog control of the 0- to 2-pi phase for each of the p x p microwave signals actuating an active antenna. These signals originate from the coherent detection of a dual frequency laser beam obtained with an acoustooptic frequency shifter. Experimental results obtained at a microwave frequency of 1.8 GHz are presented.

A 30 GHz, HEMT, Active Antenna Structure in MMIC Technology

Abstract: A novel MMIC active antenna structure has been demonstrated by closely integrating a HEMT device and a slot antenna on opposite sides of a GaAs substrate. To our knowledge, this is the first time that such components have been integrated on the same MMIC. It is also the first time that circuit components have used both sides of an MMIC with via holes providing the through substrate connections. This active transmit antenna was developed for 30 GHz operation.

Integrated image-line steerable active antennas

Abstract: This paper reports a varactor-tuned Gunn oscillator constructed in an image-line circuit and integrated with a grating antenna. The combined circuit exhibited a 2 percent electronic tuning range corresponding to a frequency steerable range of 4 degrees. The active antenna demonstrated a clean spectrum with low side lobes. The beam angles agree very well with the prediction. The circuit can be produced at low cost and should have many applications at millimeter-wave frequencies

Offset active antenna having two reflectors

Abstract: An offset type active antenna having two reflectors in a periscopic configuration. A radio lens is provided at the focii of the two reflectors. It comprises a collector and a primary array that is considerably larger in size than the collector. The "small" sources of the collector are in a geographically identical one-to-one correspondence with the "big" sources of the primary array, and they are respectively connected together via devices for providing fine phase adjustment.

Active integrated microstrip antenna

Abstract: An antenna element suitable for use in a phased array antenna comprises a travelling wave structure (60) formed by a plurality of microstrip transmission line segments (R1-Rm) connected in series by one or more active circuit devices (A1-Am-1). The active circuit devices are controllable to modify the phase and/or magnitude of the signal propagating in the travelling wave structure. The active circuit devices provide the capability to control electronically the radiation pattern of the individual elements by modifying the phase and/or magnitude of the signal in different line segments. Such active antenna elements may be fabricated in various configurations, for example circular, linear and folded. The active circuit devices may comprise phase shifters and/or time delay shifters and/or amplifiers and/or alternators.

Method and device for the rejection of harmonics emitted by an active antenna having electronic scanning

Abstract: The method relates to active antennas having electronic scanning and consisting of an array of radiating elements (Eo,...Em) excited on emission by individual power amplifiers (Ao,...Am) arranged in active modules (M'o,...M'm) placed as close as possible to the radiating elements (Eo,...Em). It consists in reducing the level of the harmonics emitted by dividing the power amplifiers (Ao,...Am) into at least two groups and by impressing upon the power amplifiers (Ao,...Am) a non-zero common value of phase shift phi which is added to the individual values of phase shift which are required by the electronic scanning and which is obtained, for one of the groups, at the input of the power amplifiers and for the other group at the output of the power amplifiers. The common value of phase shift phi is advantageously taken equal to pi in order to reduce the even harmonics or pi /2 in order to reduce the odd harmonics. The reduction in the level of the harmonics is due to the fact that the latter no longer add together in phase in the signal from the active antenna but with a phase difference equal to (n-1) phi , n being the order of the relevant harmonic.

Method for reduction of side lobes in a radiation pattern of an active antenna array and antenna using the method

Abstract: The present invention relates to a method making it possible to reduce the side lobes of the radiation pattern of an antenna array comprising a plurality of active modules, as well as to an antenna implementing this method. The method consists in supplying the active modules, symmetric with respect to the centre of the antenna, with the same constant supply voltage, the value of which is defined on the basis of the power distribution law which it is desired to obey, generally Gaussian in shape. The invention applies just as well to linear antenna arrays as to two-dimensional antenna arrays or space-filling antennas.

Compact active antenna for weather satellite.

Abstract: The subject of the invention is a meterological antenna. It includes one or more correctly-phased directional antennas (2, 3) of the QUAGI type with a mechanical gain of more than 15 dBd, the said antennas (2, 3) are equipped with a directional device and are activated and amplified by means of a low-noise preamplifier (4) arranged at the entrance to the plastic protection (1) so as to be able to place the receiver any distance from the meteorological antenna. The directional antennas (8, 9, 10, 11) are actuated by three servomotors (12, 13, 14), two servomotors (12, 13) control the antenna as a function of the geographical position of the boat and the third servomotor (14) is slaved to an electronic compass, and the meteorological antenna assembly is provided with a self-stabilising device. Antenna for weather satellite for mobile or maritime installation.

Method for controlling an active antenna

Abstract: A method for controlling an active antenna of individual transmitting/receiving elements, an optical beat signal being generated in the microwave frequency range by heterodyning two optical frequencies and, after electro-optical conversion, being applied with defined phase and amplitude to the individual transmitting/receiving elements of the antenna.

On-vehicle satellite broadcast reception system

Abstract: PURPOSE:To receive a satellite broadcast even in a cabin of an automobile. CONSTITUTION:An omonidirectional plane antenna 2 receiving a radio wave from an artificial satellite is arranged onto the roof 1 of a vehicle or a position in parallel with the roof 1, a satellite broadcast signal received by the plane antenna 2 is led to a superconducting mixer via an amplifier, in which the signal is down-converted, or an active antenna is arranged to the roof 1 of the vehicle or the like, and the satellite broadcast signal received by the active antenna is led to the superconducting mixer directly, in which the signal is down-converted.

Integrated with cpw/aperture coupled patch antenna

Abstract: A new design of an active antenna with a dielectric resonator stabilized HEMT oscillator (DRO) and an aperture-coupled patch antenna is reported. The circuit is fabricated using coplanar waveguide (CPW) with the oscillator and the antenna on opposite sides of the substrate. The active antenna was demonstrated at 7.6 GHz; however, the design can be scaled to higher frequencies. Excellent oscillator characteristics and radiation pattern have been obtained.

Broadband Active Antenna

Abstract: Effective area of search coil increased Input impedance presented by operational amplifier and associated components nearly balances out impedance of search coil Fluctuations in ambient magnetic field induce large currents in search coil

Active antenna for bidirectional communication

Abstract: PURPOSE: To provide an active antenna for bidirectional communication. CONSTITUTION: An active antenna is incorporated in the terminal station of a system for performing the replacement of data with a central station on the basis of the modulation of a microwave carrier. The modem of the active antenna is constituted of one transistor 10 and the bias current of the transistor is changed over between a low value at a time of demodulation and a high value at a time of modulation. This changeover is obtained by a circuit equipped with three resistors (Rd, Rdg, Rg). These resistors are changed over by two transistors 13, 14 connected to the resistors in parallel and these transistors are controlled by two signals M1, M2 transmitted from the control circuit of the terminal station. The active antenna can be adapted, for example, to the remote control of a charge payment system, remote automatic cash payment, the determination of the position of moving matter or long distance data replacement.

Transmission line equivalent circuits for 2-D active grid antenna arrays

Abstract: Two-dimensional active grid arrays are being investigated for the submillimeter frequency range. The quasioptical Josephson oscillator is a large 2-D array of active antennas. Each active antenna consists of an active device integrated with a short antenna. For the active device, the Josephson function is used. Because of the extremely small power output of the single oscillator ( approximately nW), a large array of active antennas needs to be employed. The power radiated from each active antenna is quasioptically combined using the Fabry-Perot type cavity to give useful power levels. The arrays are designed for baseband operation, i.e. for the broad frequency range below the first array resonance. Several grid arrays have been measured and characterized. Of the four arrays considered, the slot array has the smallest input impedance and the dipole array has the highest. The bow-tie array represents the best combination of the wide baseband operating range and moderate driving point impedance. >

High T/sub c/ superconducting active antenna with reflector

Abstract: A high-T/sub c/ superconducting (SC) active antenna with a corner reflector is found to be useful for detecting electromagnetic waves (f=955 GHz) The SC active antenna is a new type of antenna which consists of material properties and antenna properties The microwaves with fixed polarizations are radiated to the SC active antennas, and the detectivities and the directivities were confirmed experimentally With the use of the corner reflector, the sensitivity and the directivity can be improved >

Method for forming radiation pattern of high- efficiency active antenna for electronic scanning radar and antenna for performing method thereof

Abstract: PURPOSE: To enhance a power efficiency and to enable mounting and use of the antenna on a satellite by changing a usage of an active antenna element in transmission and reception and by making it a pattern optimum for each of transmission and reception CONSTITUTION: An active transmission/reception (TR) module has a transmission input E, a transmission output S connected to an emission element of an antenna, a digital phase shifter 10 and a head-to-tail type parallel connection of a high power amplifier(HPA) 13 for transmission and a low noise amplifier(LNA) for reception between first and second switches 11 and 12 A gain control is given by adding one variable attenuator 15 behind the LNA 14 and controlling a gain in a final stage of the LNA 14, and the whole of the HPA 13 operates continuously in an output power By making the HPA 13 operate in a region of compression or saturation thereof, accordingly, it is possible to maximize the output power and to optimize the efficiency thereof The output switch 12 gives transmission-reception switching and two ports leading to the emission element (two polarizations: horizontal polarization H and vertical polarization V) at the same time

Millimeter-wave quasi-optical and spatial power combining techniques

Abstract: : This report summarizes the research activities carried out in Electromagnetics and Microwave Laboratory, Department of Electrical Engineering, Texas A and M University The project was sponsored by the US Army Research Office under contract No DAALO389-K-0085 The topics of investigation included active antenna elements, spatial power combining and injection-locking, quasi- optical components, novel planar slotline and coplanar waveguide circuits, and other circuit developments and analyses A list of publications and a report of invention are included Quasi-Optical Techniques, Microwaves, Millimeter-Waves, Power Combining, Active Antennas