Showing papers on "Antenna (radio) published in 1991"

The first demonstration of an optically steered microwave phased array antenna using true-time-delay

Abstract: The concept of true-time-delay steering for phased array antennas and its advantage over phase shifters in broadband applications are described with particular emphasis on the potential advantages offered by fiber-optic delay lines. The system architecture of the phased array antenna and the design and performance of the fiber-optic time-shifter networks in the antenna are described. The radiation patterns of the phased array antenna at L and X bands are presented. Using semiconductor laser switching to implement the delay times, the absence of beam squint in the antenna pattern and its frequency was switched from L to X band is demonstrated. >

Spaceborne radar measurement of wind velocity over the ocean-an overview of the NSCAT scatterometer system

Abstract: Scatterometry and scatterometer design issues are reviewed. The design of the NASA Scatterometer (NSCAT) to be flown on the Japanese ADEOS mission is presented. Building on Seasat experience, the NSCAT system includes several enhancements, such as three antenna azimuths in each of two swaths, and an onboard digital Doppler processor to allow backscatter measurements to be colocated everywhere within the orbit. These enhancements will greatly increase the quality of the NSCAT wind data. The ground processing of data is discussed, and scatterometers of the next decade are briefly described. >

Millimeter-wave design of wide-band aperture-coupled stacked microstrip antennas

Abstract: K-band aperture-coupled stacked microstrip antennas are studied and numerical results based on the solution of integral equations solved in the spectral domain are presented. The effects of varying physical parameters of the structure are investigated with the goal of designing millimeter-wave wideband microstrip antennas. Antennas with different characteristics are then analyzed and compared with experimental data. Bandwidths in excess of 20% are obtained and applications to phased array antennas are discussed. >

An adaptive array for mobile communication systems

Abstract: The use of adaptive antenna techniques to increase the channel capacity is discussed. Directional sensitivity is obtained by using an antenna array at the base station, possibly both in receiving and transmitting mode. A scheme for separating several signals at the same frequency is proposed. The method is based on high-resolution direction-finding followed by optimal combination of the antenna outputs. Comparison with a method based on reference signals is made. Computer simulations are carried out to test the applicability of the technique to scattering scenarios that typically arise in urban areas. The proposed scheme is found to have great potential in rejecting cochannel interference, albeit at the expense of high computational requirements. >

Improved coupling for aperture coupled microstrip antennas

Abstract: An aperture shape that gives significantly improved coupling for an aperture coupled microstrip antenna is described. This ‘dogbone’ aperture consists of the usual rectangular slot, augmented with loading slots at each end. Measured data show an increase of more than three for the resonant input impedance of an antenna using the dogbone-shaped aperture, as compared with the input impedance of the same antenna with a rectangular slot of the same overall length. The field distributions of both slots are also measured, and compared.

Spread spectrum transmitter power control method and system

Abstract: A power control system for a cellular mobile telephone system in which system users communicate information signals between one another via at least one cell site using code division multiple access spread spectrum communication signals. The power control system controls transmission signal power for each cellular mobile telephone in the cellular mobile telephone system wherein each cellular mobile telephone has an antenna, transmitter and receiver and each cell-site also has an antenna, transmitter and receiver. Cell-site transmitted signal power is measured as received at the mobile unit. Transmitter power is adjusted at the mobile unit in an opposite manner with respect to increases and decreases in received signal power. A power control feedback scheme may also be utilized. At the cell-site communicating with the mobile unit, the mobile unit transmitted power is measured as received at the cell-site. A command signal is generated at the cell-site and transmitted to the mobile unit for further adjusting mobile unit transmitter power corresponding to deviations in the cell site received signal power. The feedback scheme is used to further adjust the mobile unit transmitter power so as to arrive at the cell-site at a desired power level.

Microstrip Yagi array antenna for mobile satellite vehicle application

Abstract: A novel antenna structure formed by combining the Yagi-Uda array concept and the microstrip radiator technique is discussed. This antenna, called the microstrip Yagi array, has been developed for the mobile satellite (MSAT) system as a low-profile, low-cost, and mechanically steered medium-gain land-vehicle antenna. With the antenna's active patches (driven elements) and parasitic patches (reflector and director elements) located on the same horizontal plane, the main beam of the array can be tilted, by the effect of mutual coupling, in the elevation direction providing optimal coverage for users in the continental United States. Because the parasitic patches are not connected to any of the lossy RF power distributing circuit the antenna is an efficient radiating system. With the complete monopulse beamforming and power distributing circuits etched on a single thin stripline board underneath the microstrip Yagi array, the overall L-band antenna system has achieved a very low profile for vehicle rooftop mounting, as well as a low manufacturing cost. Experimental results demonstrate the performance of this antenna. >

Position sensitive power transfer antenna

Abstract: A power supply implanted behind a tissue barrier in a human body and operating a medical device and incorporating a high frequency power receiver antenna coil; a transmitter having a high frequency transmitter antenna coil generating high frequency power and transmitting the power from the transmitting coil to the implanted receiver coil; an implanted non-ferrous magnet affixed within the implanted annular receiver coil; and a magnetic field sensing device or magnetically operated reed switch affixed concentrically within the transmitter coil of the transmitter and controlling transmission of high frequency power from the transmitter to the implanted power supply.

Near-field antenna measurements

Abstract: Near-field measurement concepts near-field measurements microwave interferometer coordinate measurements and machining small near-field measurement systems robotic systems design operations near-field measurement error analysis. List of acronyms. List of symbols.

Path loss, scattering and multipath delay statistics in four European cities for digital cellular and microcellular radiotelephone

Abstract: The authors present typical and worst-case root mean square (RMS) delay spreads and excess delay spreads (10 dB) and mean channel path loss at 900 MHz in four European cities using typical cellular and microcellular antenna locations. Several thousand power delay profile measurements were made at six typical cellular and microcellular base station locations in the four cities. The data were obtained at local worst-case time-dispersion locations over hundreds of kilometers of typical operating routes, such as highways, bridges, and city streets, and form the basis for statistical models which can be used to predict the percentage of locations or the percentage of time in which channels will possess particular values of RMS delay spread and excess delay spread. The effect of reference distance on wideband path loss and the propagation path loss laws for cellular and microcellular radio channels are given. Radar cross sections computed from the data for typical scatterers in cellular and microcellular radio channels are given. >

Electromagnetic antenna collimator

Abstract: A dielectric inset mountable within a conical horn antenna for focusing an impinging electromagnetic wave front as a planar wave front at an attached wave guide. In one construction a homogeneous inset having an ellipsoidal forward surface and conical aft surface is fitted into a double flared conical antenna including a cylindrical, hybrid mode matching section. In various alternative compound constructions, materials of differing dielectric constants and geometrical shapes are arranged to facilitate a size and weight reduction of the inset and focus the incident wave front relative to the wave guide. In other embodiments, still lower density materials, including suspended metallic particulates are used.

Fiber optic microcellular radio

Abstract: A distributed antenna system consisting of optical fiber connected canisters is proposed to replace or supplement the base station antennas required for cell splitting of growing cellular mobile radio systems. The end-to-end linear transmission of RF signal voltage can be maintained over the wide dynamic range of mobile radio. The technical feasibility of multiplexed subcarrier transmission using available lightwave components has been verified by signal-to-noise ratio and intermodulation distortion measurements. Measurements of a two-way audio link over both simulated and real radio paths have demonstrated the compatibility of a prototype lightwave transceiver, designed for the canister, with the existing base station and mobile equipment. >

Antenna selecting diversity receiving apparatus

Abstract: The apparatus is used in a TDM system with a linear modulating wave (BPSK, QPSK or 16 QAM) and has an integrating circuit 15 which integrates the signals from antennas 11, 12 for respective predetermined time periods prior to the start point of each TDM time slot allotted to the receiver 14 in order to select which antenna should be used during that time slot. The selection may be effected by a comparator 17 which compares the integrated signal from one antenna with that from the other previously integrated and retained in a sample and hold circuit 16. A further comprator (19) may be provided operative during an allotted time slot for repeatedly comparing the integrated signal with a reference so that changeover between antennas is effected if the integrated value is below the reference, (Figs 10, 11). In an alternative embodiment, (Figs 12, 13), prior to an allotted time slot, the signal from each antenna 11, 12 is integrated for multiple respective predetermined time periods, and from the integrated values a prediction of the signal level during the time slot is made for each antenna. The antenna to be used during the time slot is selected in dependence on the predicted levels.

Method and apparatus for dynamic distribution of a communication channel load in a cellular radio communication system

Abstract: A method and apparatus is provided for dynamic distribution of a communication channel load of sectorized-antennae or omni-directional antennae of cell sites in a cellular radio communication system. The channel load is distributed by narrowing an antenna (102) beamwidth of an overloaded sector of a cell site (100) and widening an antenna (104) beamwidth of an adjacent sector of the cell site (100). In an alternative embodiment, the channel load is distributed by reducing power of an antenna (124) of a cell site (120) which is adjacent to an overloaded cell site (100). Alternatively, the channel load is distributed by increasing power of an antenna (118) of a cell site (116) which is adjacent to an overloaded cell site (100). Subsequent to the channel load distribution, each of the subscriber units in the overloaded (100) and adjacent cell sites (116, 120) are handed off to the particular cell site which is best able to service the subscriber units.

Reconfigurable arrays by phase-only control

Abstract: Due to space or cost reasons, a single array antenna can be required to radiate more than one pattern, each pattern being selected by an electronic control, in which only the phase can be modified. A synthesis method for such a problem that is able to determine both the common amplitude and the various phases in an integrated way is presented. Moreover, the approach is flexible enough to take into account additional constraints and allows an efficient implementation. Some test cases showing the effectiveness of the method are presented. >

Design of multioctave spiral-mode microstrip antennas

Abstract: The design of spiral-mode microstrip antennas with a bandwidth of 6:1 is demonstrated. The antenna has a small dissipative loss due to a resistive loading outside its active region. As a specific measure of bandwidth at microwave frequencies, the spiral-mode microstrip antenna gain is higher than that of the conventional loaded-cavity spiral over a 5:1 and if the spacing d between the microstrip and the ground plane is 0.25 in. or larger over the 2-12 GHz range. Cursory efficiency calculations show consistent improvement over a loaded-cavity spiral. A study of ground plane spacing showed that the antenna gain remains above the conventional spiral gain as d is reduced until it is as small as 0.1 in. >

Telemetered patient location system and method

Abstract: A system and method for locating patients in a hospital using M different frequency patient transmitters and N fixed location antennas within the hospital for receiving the patient signals. The received signals for each antenna are separated from the signals received by the other N-1 antennas, and the signal strength of each signal received by each antenna is measured. The received signal strength of each antenna is processed to determine which of the antennas received the strongest signals from each of the patient transmitters. Alternatively, the approximate location within the hospital of each operating patient transmitter is determined since the antennas are in fixed locations and the layout out of the hospital is known. In other embodiments, each of the antennas have a different modulation pattern to enable identification of which of the antennas receives which signals from the patient transmitters. The M signals received by the N antennas are separated by the frequencies of the patient transmitters with each of the separated signals being a composite signal having a single frequency and modulation components from each of the N antennas. Then the signal strength of each of the separated signals is measured, and the relative contribution to the measured signal strength from each of the N antennas is determined. Finally, the relative contribution information for each patient transmitter frequency from each antenna is processed to determine which of the antennas received the strongest signals from each of the patient transmitters to locate the patient relative to particular antennas.

Plural frequency patch antenna assembly

Abstract: A microstrip patch antenna assembly (20, 52, 106) is formed of a patch radiator (24, 58) and a feed structure (26, 64) of microstrip feed elements (48, 50, 66, 68) disposed on opposite sides of a ground-plane element (22, 54) and spaced apart therefrom by layers (28, 30, 72, 74) of dielectric material. A single slot (108) or a pair of orthogonally positioned slots (44, 46, 82, 84) within the ground-plane element couples linearly or circularly polarized microwave power from the feed structure to the patch radiator. Additional radiators (60, 62) may be stacked above the foregoing radiator, the radiators being separated by further layers (76, 78) of dielectric material. A plurality of square-shaped radiators (58, 60, 62) may be employed for multiple-frequency operation in which case the radiator size and the thickness of dielectric material between the radiator and the ground-plane element establish a resonant frequency. A single radiator (24) of rectangular shape may be employed for radiation at dual frequencies wherein short and long edges of the radiator are each equal to one-half of the respective wavelengths in the dielectric material. An array (124) of the antenna assemblies can be constructed in monolithic form for development of a steerable beam of electromagnetic radiation.

Radio base station for mobile communication

Abstract: PURPOSE:To solve problems such as the difficulty of land obtaining and undesivable influence to be extended upon the scenery of a city in respect to a radio base station for mobile communication such as an automobile telephone. CONSTITUTION:The radio station is provided with a strut 30 for supporting a street lamp, an antenna 20 mounted on the strut 30, a connection terminal to a cable transmission line 40 connected to a telephone exchange network, transmitting/receiving parts 12, 13 connected between the connection terminal and the antenna 20, a power supply part 15 for receiving AC power from a feeder 32 shaved with the street lamp and supplying operation power to the transmitting/receiving parts 12, 13, and a body part 10 fixed to the inside of the strut 30.

Photon-noise-limited laser transducer for gravitational antenna

Abstract: We have constructed and tested a laser interferometer transducer for a long, wideband, laser-linked gravitational radiation antenna. Photon-noise-limited performance was achieved using 80 microW from a single mode Spectra-Physics 119 laser in a modified Michelson interferometer on a vibration isolation table in a quiet room. A piezoelectric driver on one of the interferometer mirrors was used to generate subangstrom (3 x 10(-14)-m) vibrations of known amplitude. The measured displacement sensitivity of the system in the kilohertz region was 1.3 x 10(-14)m/Hz(1/2), which compares well with the calculated photon noise limit of 1.06 x 10(-14) m/Hz(1/2). This is the smallest vibrational displacement measured directly with a laser to date.

A new class of resonant antennas

Abstract: A new class of wire antennas called meander antennas is introduced as possible elements for size reduction. Efficiency is affected only by the ohmic losses in the wire, and cross polarization is negligible. An increase in the number of meander sections introduces less size reduction in return for an improved bandwidth. These antennas can be used to reduce the size of existing wire antennas such as Yagi-Uda antennas and log-periodic dipole arrays. A size reduction in the resonant length typically from 25-40% is obtained. More size reduction is obtained by decreasing the radius of the wire or increasing the separation of the folded arms. >

Microwave applicator for transurethral hyperthermia

Abstract: A radiant heating apparatus for deployment within an animal body to radiate heat-producing electromagnetic energy into the body includes an antenna mounted on a catheter element and connected to an electrical transmission line having first and second conductors for feeding electrical current from a source to the antenna. The apparatus has the improvement in which the antenna comprises a first radiating element carried on the catheter element and extending from an antenna feed junction in a first direction along a first elongation axis. The first radiating element is connected to the first transmission line conductor at the feed junction and presents a first selected impedance to the feed junction. A second radiating element is carried on the catheter element and extends from the feed junction in a second direction opposite to the first direction along the first axis. The second radiating element is connected to the second transmission line conductor and presents a second selected impedance to the feed junction. The first and second radiating elements radiate electromagnetic energy outwardly from the feed junction upon being excited from the transmission line with alternating electrical current within a selected frequency range. The first and second radiating elements are arranged for presenting the first and second impedances and for providing the radiation substantially independently of the length of the catheter element inserted within the animal body beyond the full insertion of the first or second radiating elements within the animal body. This invention was made in part with government support under contract number NIH/NC1 R01 CA23549 awarded by the National Institute of Health. The government has certain limited rights in the invention.

A slot design for uniform aperture field distribution in single-layered radial line slot antennas

Abstract: A single-layered radial line slot antenna (RLSA) is proposed for a direct broadcast from a satellite (DBS) subscriber antenna. It utilizes a radially outward-traveling wave and the aperture field is intolerably tapered if the uniform slots are used. Two novel techniques are applied. First, the slot design for uniform aperture field distribution is introduced. Second, the radial line is terminated by a matching spiral, in place of a dummy load. It suppresses reflection and radiates all the residual power in circular polarization. For a model antenna of 600-mm diameter, the efficiency of 65% is observed. >

Coplanar multiple loop antenna for electronic article surveillance systems

Abstract: An antenna for transmitting electromagnetic energy for deactivating a resonant tag circuit of an electronic article surveillance tag without regard to the orientation of the tag while minimizing far field radiation. The antenna includes a substantially planar dielectric substrate having a first side and a second side. The antenna also includes four substantially coplanar conductive loops on the first side of the dielectric substrate. The conductive loops are arranged in a two-by-two sequence and connected in series such that current flowing through any one of the conductive loops is out of phase with respect to current flowing in each adjacent conductive loop. The antenna also includes a ground trace on the second side of the substrate.

Serrated-roll edge for microwave antennas

Abstract: The invention presents an optimum method and mean for reducing the side robes of microwave antennas whether mounted or through the serrated-roll treatment of their edges. The reduction of side robes leads to the enhancement of the main robe, the suppression of the unwanted electromagnetic interference, the improvement of antenna performance, as well as lowering the size of antenna.

Stacked dual dipole MMDS feed

Abstract: A multichannel, multipoint distribution services (MMDS) dipole antenna for receiving multiple channels in the S-band frequency range of 2000 and 3000 MHz is formed from a printed circuit board which is directly connected to a coaxial cable. On the printed circuit board are etched two stacked dipoles. Each of the dipoles has a first one-half element etched on the first side of the printed circuit board and the second one-half element etched on the second side of the printed circuit board. The first and second dipoles are oriented to be in phase with each other and are separated from each other at a wavelength spacing between 0.25 lambda and 0.40 lambda. The antenna of the present invention further uses a phase combining circuit and an impedance matching circuit etched on the printed circuit board for combining in phase the polarized signals, for canceling the non-polarized signals at 0° and 180°, from the two stacked dipoles and for matching the impedance from the two dipoles to the impedance of the coaxial cable.

Single reference, three target calibration and error correction for monostatic, polarimetric free space measurements

Abstract: The authors present a scheme for absolute calibration of a polarimetric scattering range. All free-space polarimetric radar cross section (RCS) and antenna measurements are subject to errors like coupling and residual reflections. The modeling of these errors results in a 12-term error correction. The procedure for the error correction with three linear independent calibration targets and an isolation measurement is shown. Based on network analysis, a single reference calibration is introduced. This single reference calibration requires the precise calculation of only one reference target. As single references, spheres or flat plates are used. The references of the other targets are determined by the calibration procedure. The single reference calibration is suitable for all narrow and wideband, complex, polarimetric RCS, and antenna measurements. Measurements are shown for different targets which demonstrate the benefits of the single reference calibration. >

Tire pressure monitoring system

Abstract: A wireless tire pressure monitoring system warns a driver of a vehicle of low pressure in one or more of its tires so that the driver may take corrective action before a tire blowout occurs. A pressure transducer, transmitter and antenna are integrally housed and mounted to the tire stem of a tire. When the pressure transducer senses a tire pressure below a preselected pressure, the transmitter broadcasts a radio frequency (RF) signal that, upon detection by a receiver mounted on the vehicle, warns the driver of abnormally low pressure. In a preferred embodiment, the transmitter is a SAW device that is periodically interrogated by an RF signal from a transmitter on the vehicle.

Circularly polarized dielectric antenna

Abstract: PURPOSE: To provide a radiator whose axis ratio is excellent suitable for a primary radiator for a parabolic antenna in spite of small sized light weight configuration. CONSTITUTION: The front end of the antenna is provided with a circular waveguide 1 to which a couple of rectangular notches 2 are formed symmetrically, a dielectric section 3 made of a dielectric body inserted to the front end of the circular waveguide 1, a short-circuit plate 4 short-circuiting the tail end of the circular waveguide 1 and an exciting probe 5 arranged toward the front side from the short-circuit plate at the surrounding wall of the circular waveguide 1 by a 1/4 wavelength with respect to the operating center frequency. Thus, the directivity is adjusted by a length l of the dielectric section 3 at the outside of the circular waveguide 1 and the amplitude and phase of each of horizontal and vertical polarized wave components are independently adjusted by the depth and angle of the notch 2 formed to the front end of the circular waveguide 1. COPYRIGHT: (C)1992,JPO&Japio

System for simultaneously deriving position information from a plurality of satellite transmissions

Abstract: A method and a system are disclosed for measuring the baseline vector b between a pair of survey marks on the ground by radio interferometry using radio signals broadcast from the earth orbiting satellites of the NAVSTAR Global Positioning System (GPS), the radio signals broadcast by the satellites being double-sideband modulated with their carriers suppressed The signals received by one antenna during a predetermined time span are separated into upper and lower sideband components These separate components are filtered, converted to digital form, and then multiplied together Differences in Doppler shift are utilized to distinguish the carriers of different satellites Thus, the powers and carrier phases of the signals from a plurality of satellites are measured simultaneously and numerical data representing the measurement results are obtained at each survey mark The measurements are performed in real time at each mark without reference to signals that are received at any other place and without knowledge of any of the coded signals that modulate the GPS carriers