Showing papers on "Active antenna published in 1994"
01 Jun 1994
TL;DR: In this article, a new radiating element is presented, which can provide simultaneously a large bandwidth and high gain, and it consists of four identical patches uniformly displayed within a rectangular aperture and fed electromagnetically by a driven patch etched on a lower substrate.
Abstract: A new radiating element is presented, which can provide simultaneously a large bandwidth and high gain. It consists of four identical patches uniformly displayed within a rectangular aperture (2*2) and fed electromagnetically by a driven patch etched on a lower substrate. It is shown that a good coupling with the parasitic patches is obtained, causing a large bandwidth, and the resonance modes of each patch are excited in phase, giving a high gain.
87 citations
Proceedings Article•
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TL;DR: This paper proposes a new active sensor system (Active Antenna) which consists of only four components, an insensitive flexible beam, a position sensor, a torque sensor and an actuator, and shows that this sensor system enables us to detect the shape of this object when it is mounted on the front part of a mobile robot.
Abstract: This paper proposes a new active sensor system (Active Antenna) which is motivated by the antenna of an insect. Insects use their antennae skilfully so that they can avoid hitting objects, while they are crawling, running, and even when they are staying still. The antenna can be characterized by its "flexibility" and "active motions". Based on the observations on insect's antenna, we propose a new active sensor system which consists of only four components, an insensitive flexible beam, a position sensor, a torque sensor and an actuator. We will show that this simple sensor system can locate any contact point between the insensitive flexible beam and an object by applying an active motion to the beam. We will also show that this sensor system enables us to detect the shape of this object when it is mounted on the front part of a mobile robot. Finally, we have designed and developed an active sensor system based on our idea and have verified the working principle by experiments. >
63 citations
TL;DR: Co- and cross-polar radiation patterns in E- and H-plane prove that the antennas also have favorable radiation characteristics in a wide bandwidth (at least 18%) and are presented that allows the straightforward and optimal design of transmitting and receiving antennas with multiple active stages.
Abstract: This paper deals with the design of broadband active microstrip antennas where the amplifier is integrated with the radiator. Theoretically sound definitions for gain and noise figure of the active antenna are introduced, and their relationships with the definitions for the composing circuit and radiator parts are explained. A sequential design procedure is presented that allows the straightforward and optimal design of transmitting and receiving antennas with multiple active stages, taking into account input and output matching, the gain-versus-frequency curve as well as the noise performance. The theoretical concepts are illustrated with two examples: one of a transmitting active antenna and one of a receiving antenna. The former one is a two-stage design that achieves nearly 25% of bandwidth with regard to gain and matching and 24 dB gain improvement as compared to the matched passive antenna. The second one is a receiving antenna (one stage) with a measured noise figure of 1.2 dB in a bandwidth of over 17% and a gain improvement of 11.9 dB over the corresponding passive antenna. Finally co- and cross-polar radiation patterns in E- and H-plane prove that the antennas also have favorable radiation characteristics in a wide bandwidth (at least 18%). >
44 citations
01 Jan 1994
TL;DR: In this paper, the radiation characteristics of a probe-fed microstrip patch loaded with a varactor diode were investigated, and it was shown that large effective bandwidths can be achieved using varactor diodes, although at the expense of reduced antenna efficiency and increased cross-polarisation levels.
Abstract: A thorough investigation of the radiation characteristics of a probe-fed microstrip patch loaded with a varactor diode is presented. The theoretical analysis used to model this structure incorporates the full-wave spectral domain integral technique in conjunction with an equivalent circuit model of the varactor diode. Attachment modes are used to accurately model the current through the feed and load. Very good agreement between theory and measurement was obtained. From this investigation, the advantages and drawbacks of using varactor diodes to improve the radiation characteristics of a microstrip patch antenna were established. It was shown that large effective bandwidths can be achieved using varactor diodes, although at the expense of reduced antenna efficiency and increased cross-polarisation levels.
39 citations
TL;DR: In this paper, an active antenna array with optical input and beam scanning capability was developed, where the phase shift between antenna elements was controlled by means of unilateral injection locking, and the reference signal for injection locking was launched into an optical fiber by a multiquantum-well InGaAs-InGaAsP distributed feedback laser.
Abstract: An active antenna array with optical input and beam scanning capability was developed. The phase shift between antenna elements is controlled by means of unilateral injection locking. The reference signal for injection locking is launched into an optical fiber by a multiquantum-well InGaAs-InGaAsP distributed feedback laser. The RF signal is recovered by a photodetector at the other end of the link and fed to the RF circuit. Experimental results are presented and discussed. >
29 citations
TL;DR: In this paper, a two-dimensional planar array of weakly coupled active circular patch antennas suitable for quasi-optical power combiners is discussed, and a novel radiating element that has low cross-polarization is described.
Abstract: This paper discusses two-dimensional planar arrays of weakly coupled active circular patch antennas suitable for quasi-optical power combiners. A novel radiating element that has low cross-polarization is described. A two-dimensional array analysis was developed to address radiation pattern and phase problems. Equivalent isotropic radiated power levels of 1.5 W for a two by two FET array and 3.8 W for a two by four FET array have been obtained at X-band. >
23 citations
TL;DR: In this paper, a polarisation-agile active antenna has been constructed and tested, which consists of two varactor diode loaded active patches using npn bipolar transistors in the common base configuration as sources.
Abstract: A polarisation-agile active antenna has been constructed and tested The radiation can be selected to be circularly polarised in either sense, or linearly polarised in the vertical, horizontal or either diagonal plane The antenna consists of two varactor diode loaded active patches using npn bipolar transistors in the common base configuration as sources, and with the patch axes at right angles to each other The two oscillators are locked to an external source, and the phase from each patch element is controlled by varying the diode bias voltage By appropriate combination of the phase relationships, the various polarisations are produced
23 citations
23 May 1994
TL;DR: A new planar transponder integrating a self-oscillating mixer (SOM) and active antennas is presented and was successfully operated up to 2 m.
Abstract: A new planar transponder integrating a self-oscillating mixer (SOM) and active antennas is presented. The receiving active antenna combines a FET SOM with a patch antenna and the transmitting antenna is combined with the IF amplifier. The transponder was successfully operated up to 2 m. The design concept and the experimental result are discussed. >
22 citations
TL;DR: In this article, an FET was integrated with a cavity-enclosed inverted stripline patch antenna for low-cost microwave source operating at 5.69 GHz with an output power of 57 nW.
Abstract: An FET has been integrated with a cavity-enclosed inverted stripline patch antenna. This low-cost microwave source operates at 5.69 GHz with an output power of 57 nW. The half-power beamwidths in the E- and H-plane patterns are 46 and 64 degrees , respectively. The crosspolarisation level is nearly 20 dB down from the maximum. >
22 citations
12 Sep 1994
TL;DR: The authors show that the use of a straight antenna always makes it possible to localise the contact point irrespective of friction at the point of contact.
Abstract: This paper addresses a new active sensor system (Active Antenna) motivated by insect's antenna. The antenna can be characterized by its "flexibility" and "active motions". Based on these observations on insect's antenna, the authors' discuss an active sensor system composing of only four components, an insensitive flexible antenna, a position sensor, a torque sensor, and an actuator. The authors first consider the conditions which allow localisation of any contact point between the insensitive flexible antenna and environment by applying an active motion to the antenna. The authors show that the use of a straight antenna always makes it possible to localise the contact point irrespective of friction at the point of contact. The authors also show that contact point sensing by the use of a circular shaped antenna is weakly influenced by the friction at the point of contact. >
20 citations
23 May 1994
TL;DR: A novel technique is proposed for the measurements of the transducer power gain and noise figure of the amplifier embedded in a receiving active antenna, where the direct measurements with traditional techniques are impossible.
Abstract: A novel technique is proposed for the measurements of the transducer power gain and noise figure of the amplifier embedded in a receiving active antenna, where the direct measurements with traditional techniques are impossible. The bandwidth of the active antenna can be also determined with this technique. The good agreement between the measurements and calculations of a number of active receiving microstrip antennas shows the validity of the measurement technique. This makes it possible to characterize all the performance of receiving active antennas. >
08 May 1994
TL;DR: A dynamic active sensing system, capable of detecting the contact point between a flexible beam and an object, and it is shown that by adding a proper mass at the free end of the beam, it can make the function close to a single-valued one.
Abstract: This paper discusses a dynamic active sensing system, capable of detecting the contact point between a flexible beam and an object. The proposed sensing system is simply composed of an insensitive flexible beam, a torque sensor, a joint position sensor, and an actuator. The dynamics (such as moment of inertia and stiffness) of the sensing system changes when the motion phase switches from non-contact to contact. We show that the natural frequency during contact is generally a multi-valued function of the contact location, which is not desirable from the viewpoint of determining the contact location uniquely. It is also shown that by adding a proper mass at the free end of the beam, we can make the function close to a single-valued one. The additional mass also contributes to reducing the oscillation frequency, which releases us from treating high frequency signals. We design the hardware model based on this idea, and verify the basic principle experimentally. >
01 Oct 1994
TL;DR: The extension of the small magnetic dipole source analysis of microstrip line discontinuities to active devices is described, indicating that reduced radiation pattern perturbation will result from the active device being integrated within the periphery of the patch.
Abstract: The current interest in active microstrip antennas has highlighted the need for analysis of the radiation characteristics of such antennas. The paper describes the extension of the small magnetic dipole source analysis of microstrip line discontinuities to active devices. The analysis is then combined with the patch cavity model to form a flexible, approximate analysis suitable for implementation in active antenna computer-aided design packages. Computed results agree well with measurements and show that radiation from the active device and associated matching circuits can be significant. The analysis indicates that reduced radiation pattern perturbation will result from the active device being integrated within the periphery of the patch.
Patent•
26 Sep 1994
TL;DR: In this article, a magnetic field sensor which can be used as an active antenna is disclosed that is capable of small size, ultrawideband operation, and high efficiency, including a multiplicity of magnetic field transducers, e.g., superconducting quantum interference devices (SQUIDs).
Abstract: A magnetic field sensor which can be used as an active antenna is disclosed that is capable of small size, ultrawideband operation, and high efficiency. The sensor includes a multiplicity of magnetic field transducers, e.g., superconducting quantum interference devices (SQUIDs) that are electrically coupled in a serial array. Dummy SQUIDs may be used about the perimeter of the array, and electrically coupled to the active SQUIDs for eliminating the edge effects on the active SQUIDs. A magnetic flux transformer may be used in combination with a feedback assembly for increasing the sensitivity and linear dynamic range of the active antenna.
23 May 1994
TL;DR: In this paper, the FDTD algorithm is used to simulate a two element active antenna which is capable of three different coupled oscillation modes, and the analysis correctly predicts which modes will be stable in the steady state under different loading conditions.
Abstract: The FDTD algorithm is used to simulate a two element active antenna which is capable of three different coupled oscillation modes. This analysis correctly predicts which modes will be stable in the steady state under different loading conditions. The predicted oscillation modes, oscillation frequencies and radiation patterns are compared with experimental data. >
Patent•
12 Apr 1994TL;DR: In this paper, a T/R module or element (62) formed a part of a subarray used in an active array radar is presented. But, unlike the present paper, this paper does not consider the use of photonic interconnects for communication between levels.
Abstract: of EP0620613An electronic device operating in the microwave frequency range has components disposed in a plurality of planes (44 - 60), wherein the planes (44 - 60) are stacked vertically. The electronic device is a T/R module or element (62) forming a part of a subarray used in an active array radar. The T/R module or element (62) comprises a transmit chip, a receive chip, low noise amplifiers, a phase shifter, an attenuator, switches, DC power supply, interconnects that interconnect the foregoing components and logic circuits to control the foregoing components. The components when stacked in a 3-D package are disposed behind a radiator (44) or antenna, which transmits and receives the microwave signals. Behind the T/R module or element (62) is a manifold which provides input and output to and from the T/R module or element (62). The microwave chips of the T/R module are monolithic microwave integrated circuit chips and control logic, which are disposed in an aluminum nitride substrate and coated with a conformal hermetic coating. The 3-D chip package can optionally include microwave channel (58) cooling by adding additional layers (48). The integrated circuits also employ a flip design for mounting to the wafers. Optional photonic interconnects could be used for communication between levels in the 3-D package and can be used between subarrays as a manifold (Fig. 2).
23 May 1994
TL;DR: In this article, a polarisation agile active antenna capable of selectively radiating circular or linearly polarised radiation is presented. But the authors discuss oscillator instability considerations and initial results of active mutual coupling analysis are applicable to this antenna and a recently published active patch scanned array.
Abstract: This paper describes experimental and theoretical investigations of active antennas using injection locking techniques to achieve phase control. We present a polarisation agile active antenna capable of selectively radiating circular or linearly polarised radiation and discuss oscillator instability considerations and initial results of active mutual coupling analysis that are applicable to this antenna and a recently published active patch scanned array. >
TL;DR: A newly developed active planar array antenna which provides electronic beam-tracking without mechanical tracking equipment is presented, which uses a series-parallel fed microstrip array, electromagnetically excited array by a coplanar patch connected to theCoplanar waveguide, and low noise down-converters and self-phasing units incorporated into the feed circuits for electronic beam
Abstract: The active planar array antenna offers a number of advantages, including use as a portable antenna for easy reception of direct Ku-band satellite television broadcasts. This paper presents a newly developed active planar array antenna which provides electronic beam-tracking without mechanical tracking equipment. The features of the antenna are: (1) use of a series-parallel fed microstrip array, (2) electromagnetically excited array by a coplanar patch connected to the coplanar waveguide, and (3) low noise down-converters and self-phasing units incorporated into the feed circuits for electronic beam-tracking. The paper discusses the design of the coplanar waveguide fed coplanar patch and the configuration of a self-phasing active planar array antenna. The measured gain of the experimental 9-element unit array antenna without active devices is 13.4 dBi at 11.85 GHz. Experimental results for a 216-element self-steering planar array of size 147/spl times/220.5 mm are also presented. >
Patent•
02 Aug 1994TL;DR: In this paper, an offset active antenna with two co-focal reflectors (5,7) and a radiofrequency lens (12) at their common focus, equipped with electronic scanning in azimuth and/or in elevation, was constructed for microwave imaging by synthetic-aperture radar from a satellite circulating in low orbit.
Abstract: Offset active antenna with two co-focal reflectors (5,7) and radiofrequency lens (12) at their common focus, equipped with electronic scanning in azimuth and/or in elevation, especially for microwave imaging by synthetic-aperture radar from a satellite circulating in low orbit. The antenna is constructed according to the "Gregory" geometry, with an auxiliary reflector (7) illuminated by an active array (6) of elementary sources fed by fixed-gain amplifiers (9) with a phase imparted by variable phase-shifters (8). The beam (10) emitted by the elementary sources and reflected (14) by the auxiliary reflector (7) is focussed on the electronic lens (12), which reemits a divergent beam (17) towards the primary reflector (5), which will be reflected into a parallel beam (11). The electronic scanning of the final beam (11) is achieved by acting on the phases imparted by the primary phase-shifters (8), and possibly by phase-shifters (18) for fine adjustment in elevation.
23 May 1994
TL;DR: In this article, a 10 GHz planar quasi-optical oscillator/modulator circuit with a 3 dB modulation bandwidth of 1.4 GHz (/spl plusmn/700 MHz) is presented.
Abstract: A quasi-optical active antenna circuit with class-C amplifier characteristics can be modulated for broadband communication applications. Results from a 10 GHz planar quasi-optical oscillator/modulator circuit with a 3 dB modulation bandwidth of 1.4 GHz (/spl plusmn/700 MHz) are presented. The oscillator/modulator is linear up to a modulation index of 100%. >
01 Oct 1994
TL;DR: The applicability of a modified rectangular microstrip patch radiator for active antenna with one-port active element has been demonstrated in this paper, where the inverter line was placed inside the rectangular opening in the central part of the patch and the active patch element for the 9.1 GHz frequency was realized.
Abstract: The applicability of a modified rectangular microstrip patch radiator for active antenna with one-port active element has been demonstrated. The modified rectangular patch antenna, designed for the operating frequency of 3.4 GHz, was manufactured and tested. The inverter line was placed inside the rectangular opening in the central part of the patch. The active patch element for the 9.1 GHz frequency was realized. Co-polar and cross-polar radiation patterns, spectral purity and EIRP have been measured. Oscillating antenna using modified patch showed a higher spectral purity and substantially lower cross-polar levels in comparison with the active patch antenna realized with unmodified rectangular patch.
10 Jun 1994
TL;DR: In this paper, a 2D optical architecture based on polarization switching by N (N equals 6) spatial light modulators of pxp pixels (p equals 4) is presented.
Abstract: This paper presents recent advances toward the experimental demonstration and the far field pattern characterization of an optically controlled phased array antenna operating at 3 GHz. The 2D optical architecture is based on polarization switching by N (N equals 6) spatial light modulators of pxp pixels (p equals 4). It provides 2N-1 time delays values and an analog control of the 0 to 2(pi) phase for each of the pxp microwave signals actuating an active antenna. These signals originate from the coherent detection of a dual frequency laser beam obtained with an acousto-optic frequency shifter. Furthermore, we also present the principle of a new photodetector based on the synchronous drift of photogenerated carriers with a moving interference pattern. This moving pattern results from the interference of the two components of the dual frequency optical carrier of the microwave signal used in the above architecture. It provides a large detection volume which could yield a high saturation intensity. A theoretical analysis is detailed and followed by an experimental demonstration in GaAs at a frequency f equals 210 MHz.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Patent•
22 Jan 1994
TL;DR: In this article, a car rear window (1) heating element (3) has connecting leads (4) in which passive circuit elements are included in order to pass or block HF signals selectively to utilise the heating element as a radio antenna.
Abstract: A car rear window (1) heating element (3) has connecting leads (4) in which passive circuit elements are included in order to pass or block HF signals selectively to utilise the heating element (3) as a radio antenna. The connecting leads (4) for the power supply feed have integrated coils (6), with a capacitor (7) to block HF signal flow to the battery and bodywork. The RF output is at a connection point (10). The components are contained in heat-shrink sleeving on the cables.
TL;DR: In this paper, an active microstrip patch antenna with a GaAs MESFET on the patch periphery and the circuit acting as a self-oscillating radiating element is presented.
Abstract: This article discusses the application of a synthesis method for, and the subsequent experimental characterization, of an active microstrip patch antenna. The active antenna incorporates a GaAs MESFET on the patch periphery and the circuit acts as a self-oscillating radiating element. The MESFET and the antenna are mounted on the same side of the circuit, thereby preserving the conformal nature of the structure. The synthesis approach described is based on the method of harmonic balance and allows optimal FET terminations to be selected for a predefined, added power at a specified frequency of operation. Application of a time domain simulator is illustrated in order to demonstrate start-up performance and limit cycle formation in the presence and absence of a frequency entrainment signal. The issue of stability of the active element is also addressed using a modified device/load line method. Theoretical and experimental results are presented for the external quality factor, locking power/phase variation, and power and frequency pushing characteristics of the active antenna. Finally, the effect on oscillator behavior of the mutual coupling between the microstrip patch and the active antenna distributed embedding elements is discussed.
TL;DR: In this article, a 60 GHz-band active microstrip patch antenna using a Gunn diode as an oscillator in a reflection amplifier configuration was presented, achieving 9.26 mW at 63.24 GHz.
Abstract: The authors present a 60 GHz-band active microstrip patch antenna using a Gunn diode as an oscillator in a reflection amplifier configuration. The oscillator consists of a patch antenna, a matching and bias circuit and an Alpha Industries DGB8266 packaged Gunn diode. 9.26 mW are obtained at 63.24 GHz. A tuning bandwidth of 1 GHz is attained by varying the DC bias voltage. The radiation patterns agree well with the theory and low level crosspolarisation patterns are achieved over a broad bandwidth.
TL;DR: A far-field reflectometry setup which is capable of full polarimetric characterization of active scatterers by modulating the active element bias and using a quadrature receiver and lock-in detection scheme.
Abstract: Testing active antennas or polarimetric radar calibrators in the far field (plane wave excitation) is complicated by imperfect isolation between transmit and receive channels. We describe a far-field reflectometry setup which overcomes this problem. A large dynamic range is achieved by modulating the active element bias and using a quadrature receiver and lock-in detection scheme. A calibration method and a novel mixer phase-error correction scheme are described. The system is capable of full polarimetric characterization of active scatterers. >
01 Oct 1994
TL;DR: In this paper, a partially reflecting superstrate (dielectric cover) was used to analyze the effect of active antenna load pulling on the frequency of the active antenna in the presence of the cover.
Abstract: Active antenna load pulling effects are analysed in the presence of a partially reflecting superstrate (dielectric cover). The analytical and experimental results obtained exhibit distortion in the frequency pulling pattern of the active antenna. The results obtained can be used to design optimum cover placement or to postmanufacture tune the frequency of the active antenna module.
Patent•
18 Aug 1994
TL;DR: In this paper, an adjustable attenuator is inserted into the circuit of the active antenna between the passive part and the noise-adapted amplifier to limit the signal level in the event of antenna overvoltages, and the tuner is physically separated from the receiver and directly connected to the antenna amplifier.
Abstract: When active antennas are used for mobile receiving systems, e.g. for car radio systems, stringent requirements are imposed on the linearity of the amplifier part and on noise adaptation. This must also apply in cases where antenna overvoltages occur, in the vicinity of powerful transmitters, in urban areas, or where atmospheric discharges occur. However, the tuner input part must be protected against excessively high signal voltages. For this reason, level control is performed in the tuner upstream of the first amplifier stage. However, this has the simultaneous effect that the level obtained in the amplifier part of the antenna is sometimes not fully utilised. A number of further disadvantages of conventional mobile systems are associated with this problem, such as expensive RF cables, in some instances of considerable length, and an arrangement of the individual components in the vehicle which can be improved from an electrical/functional and technological point of view. According to the invention, an adjustable attenuator (7) is inserted into the circuit of the active antenna between the passive part (1) and the noise-adapted amplifier (2) to limit the signal level in the event of antenna overvoltages, and the tuner (3) is physically separated from the receiver and directly connected to the antenna amplifier (2) to form a module. The control voltage for the attenuator is tapped in the signal path downstream of the antenna amplifier (2). With selective attenuation of the antenna signal - i.e. depending on the selected ... Original abstract incomplete.
Proceedings Article•
01 Aug 1994TL;DR: In this article, a design methodology for a GaAs monolithic 30 GHz amplifier/antenna consisting of a HEMT device integrated with a slot radiator is presented, and both antenna numerical analysis techniques and microwave circuit CAD tools are employed.
Abstract: The increasing demand for mobile, broad bandwidth, cost-effective communications has led to the development of novel integrated active antennas operating at mm-wave frequencies. A design methodology is presented for a GaAs monolithic 30 GHz amplifier/antenna consisting of a HEMT device integrated with a slot radiator. Both antenna numerical analysis techniques and microwave circuit CAD tools are employed.