Showing papers on "Dipole antenna published in 1996"

A planar dual-frequency array antenna

Abstract: A dual-frequency array antenna having an essentially planar structure with electronic beam steering capability in both a low and high frequency band independently of each other, constructed, in a layered formation, from a top planar array antenna unit operating in the low frequency band and a bottom planar array antenna unit operating in the high frequency band. The top planar array antenna is transparent to frequencies in the high frequency band.

Phased array antenna with temperature compensating capability

Abstract: Generally, a variation of temperature at the installation site causes a phased array antenna radiation pattern to degrade. This paper describes the temperature characteristics of various components of the phased array antenna and degradations of the radiation pattern originating from temperature variations. It is effective to measure the phase distribution on the aperture and correct it, as the occasion demands, to prevent such degradations. Also, we propose a simple and effective algorithm for the measurement of the current distribution on the aperture, and present the evaluation test results of a phased array antenna with temperature compensation obtained by applying the algorithm.

Characteristics of the SAR distributions in a head exposed to electromagnetic fields radiated by a hand-held portable radio

Abstract: Presents characteristics of the specific absorption rate (SAR) distributions calculated by the finite-difference time-domain (FDTD) method using a heterogeneous and realistic head model and a realistic hand-held portable radio model. The difference between the SAR distributions produced by a 1/4-wavelength monopole antenna and those produced by a 1/2-wavelength dipole antenna is investigated. The dependence of the maximum local SAR on the distance d/sub a/ between the auricle of the head and the antenna of the radio is evaluated. It is shown that the maximum local SAR decreases as the antenna length extends from 1/4 to 1/2 of the wavelength. The maximum local SAR's in a head model with auricles are larger than these in one without auricles. The dependence of the SAR on the electrical inhomogeneity of the tissues in the head model is not significant with regard to the surface distribution and the maximum local SAR when the radio is near the head. It is also shown that the maximum local SAR is not strongly dependent on the position of the hand when the hand does not shade the antenna. Furthermore, the SAR's experimentally measured in a homogeneous head phantom are compared with the calculated SAR's.

Stacked microstrip antenna with wide bandwidth and high gain

Abstract: A stacked microstrip antenna with two parasitic elements, one of which increases the impedance bandwidth and the other which enhances the gain, has been investigated experimentally. The effects of each parasitic element have been clarified as well as the characteristics of the stacked three-element antenna and the design procedure for the stacked microstrip antenna have been described.

Experimental demonstration of a phased-array antenna optically controlled with phase and time delays

Abstract: The experimental demonstration and the far-field pattern characterization of an optically controlled phased-array antenna are described. It operates between 2.5 and 3.5 GHz and is made of 16 radiating elements. The optical control uses a two-dimensional architecture based on free-space propagation and on polarization switching by N spatial light modulators of p × p pixels. It provides 2N−1 time-delay values and an analog control of the 0 to 2π phase for each of the p × p signals feeding the antenna (N = 5, p = 4).

Dual orthogonal monopole antenna system

Abstract: An antenna system for use in wireless communication systems that is based on a pair of monopole antennas, which are electrically isolated from each other and arranged generally orthogonally. A feed circuit is coupled to the first and second monopole antennas, which connects them to a host system. Also, a ground plane conductor extends generally between the feeds for the first and second monopole antennas to improve isolation. The monopole antennas are formed on a printed circuit board, formed on first and second dielectric layers. A ground plane conductive film is disposed between the dielectric layers. The first monopole antenna is formed on an outside surface of the first dielectric layer, and the second monopole antenna is formed on the outside surface of the second dielectric layer. The second monopole antenna is arranged generally orthogonally to the first monopole antenna. The first and second monopole antennas comprise impedance matched microstrips, and the feed circuit comprises a first impedance matched unbalanced line coupled to the first monopole antenna, and a second impedance matched unbalanced line coupled to the second monopole antenna.

Ring shaped antenna

Abstract: An antenna for broadcasting omnidirectionally is disclosed. The antenna includes a cylindrical housing which has a lip which includes slots adapted to receive a patch antenna strip and a conductive ring. A GPS receiver and electronics package may be placed in the center of the housing. The patch antenna strip which includes a number of patch antennas broadcasts and receives radio signals. The conductive ring absorbs energy broadcast from the patch antennas and rebroadcasts the signal omnidirectionally. The resulting signal has a high gain and a wide bandwidth. A third embodiment in which the conductive ring is incorporated into a housing cover is also disclosed. The antenna is easily and inexpensively assembled and is more durable and reliable than prior art antennas.

A study of pulse radiation from several broad-band loaded monopoles

Abstract: Five previously proposed designs for broad-band monopole antennas are evaluated for pulse radiation. These designs use continuous resistive loading and/or discrete capacitive loading to increase the bandwidth over that of a simple, metallic monopole. The parameters for each of the designs are scaled so that the designs can be compared on a common basis (frequency range). Each of the antennas is analyzed numerically, and quantities characteristic of their pulsed performance are computed. These quantities include the reflected voltage in the feeding transmission line, radiated electric field, radiating efficiency, time-domain gain, fidelity, and symmetry when the monopoles are excited by a differentiated Gaussian pulse. In addition, the input reflection coefficient and gain at broadside for monochromatic excitation are shown. Explanations are provided for the differences in performance for these designs.

Multiband phased-array antenna with interleaved tapered-elements and waveguide radiators

Abstract: Multiband, multibeam, phased array antennas are required for today's multi-function radar and communication applications. These types of antennas play a major role in the shipboard and airborne environment, where space is limited. A single antenna is now asked to perform multiple functions, including long-range surveillance, navigation, weapons control, tracking and recognition, and electronic warfare support measures. A phased array antenna capable of covering several different frequency bands in a common aperture is highly desirable, and is currently being pursued for many of these applications. A number of multiband radar antenna configurations have been proposed in the past. An ultra-wideband phased array antenna design using interleaved waveguide elements and wideband tapered elements is presented. This phased array antenna can operate over at least three frequency bands. Numerical results of the aperture match for both types of radiators, including mutual interaction, are presented.

Novel sources and detectors for coherent tunable narrow-band terahertz radiation in free space

Abstract: A novel scheme for the optical generation and coherent detection of tunable narrow-band far-infrared radiation in free space is described. This technique involves the optical heterodyning of two linearly chirped broadband pulses to produce a quasi-sinusoidal intensity modulation at tunable terahertz frequencies. The frequency content of the narrow-band terahertz radiation produced by mixing chirped optical pulses in a nonlinear optoelectronic device such as a photoconducting dipole antenna can be tailored simply by controlling the phase modulation of the optical pulses and the delay between them. An optoelectronic terahertz beam system composed of a tunable narrow-band Hertzian dipole emitter and a synchronously gated tunable dipole detector is presented. The performance of this system as a potentially powerful tool for far-infrared pump–probe spectroscopy and the limitations produced by cubic phase modulation in the chirped optical pulses are discussed.

Antenna selection control circuitry

Abstract: Antenna selection control apparatus for a diversity antenna system including at least two antennas. The received power strength is measured from a selected antenna and compared with a reference power level. The reference power level is adjusted depending upon the signal to noise ratio of received signals, and if the selected antenna falls below the adjusted threshold another antenna is selected.

Low-cost communication phased-array antenna

Abstract: A phased-array antenna structure is provided that includes an antenna waveguide structure (404) with a plurality of waveguides (406). The antenna waveguide structure propagates the received or transmitted electromagnetic (EM) signals within the plurality of waveguides to a corresponding active array module (408). Each active array module amplifies and adjusts the phase of a received or transmitted EM signal. The active array modules are coupled to an interconnect structure (416) that provides EM signal propagation paths, as well as power and digital signal paths, to and from the active array modules. A plate (420) is coupled to the interconnect structure and the antenna waveguide structure to support the antenna waveguide structure, the electronic modules, and the interconnect structure, thereby forming a rigid unit and keeping the electronic modules in alignment with their corresponding waveguides in the antenna waveguide structure. The plate also includes waveguides for propagating the EM signals from the interconnect structure to the antenna output. The active array modules each include an integrated polarizer for selectably operating with either right-hand circularly polarized signals or left-hand polarized signals. The polarizer, amplifiers and phase shifters are mounted on a substrate in each active array module, with the substrate disposed in a position normal to the propagation of the EM signals in the corresponding waveguide of the antenna waveguide structure, resulting in a planar configuration. Further, each active array module includes a waveguide as an integral part of the active array module.

Base station equipment, and a method for steering an antenna beam

Abstract: The invention relates to a method for steering an antenna beam, and a base station equipment (100) comprising one or more antenna arrays (500, 700-704, 772-776), one or more channel units (504-508, 738-742) which channel unit comprises means (600-606, 706, 770) for phasing the signal to be transmitted and received by the antenna array (500, 700-704, 772-776) in such a way that the gain from the antenna array is the greatest in the desired direction, and means (616) for distinguishing the connection quality information from the information received from the mobile station (102). In order to improve the spectral efficiency and the connection quality, the channel unit (504-508, 738-742) comprises means (604, 732, 802) for searching for the incoming directions and delays of the received signal components, and means (604, 744, 802) for controlling the phasing means (606, 770) of the opposite transmission direction on the basis of said information and the connection quality information received from the mobile station.

Single- and dual-polarized millimeter-wave slot-ring antennas

Abstract: Single- and dual-polarized dielectric lens-supported slot-ring antennas have been developed for operation at millimeter-wave frequencies. The antennas are fed with a coplanar waveguide (CPW) to be compatible with uniplanar mixers and low-noise amplifiers, and the feedline is shown to have a minimal effect on the antenna performance. The measured antenna patterns agree well with theoretical results and have symmetric main beams, low sidelobe levels (<-15 dB), low cross polarization (<-20 dB), and 27 dB directivity. A 2/spl times/2 array of single-polarized slot-ring antennas for monopulse applications demonstrates excellent patterns at 94 GHz with -3 dB crossover power levels in both elevation and azimuth scans. The dual-polarized slot ring antenna patterns are nearly identical to those of the single-polarized antenna, and two-port isolation is as low as -25 dB. The dielectric lens-supported slot-ring antenna is an excellent candidate for compact, low-cost millimeter-wave systems with fixed or variable polarization capabilities.

Radio frequency antenna with current controlled sensitivity

Abstract: An antenna circuit configured for use in a radio frequency data communications device has an antenna constructed and arranged to transfer electromagnetic waves, the electromagnetic waves corresponding to a signal carried by the antenna and generated from a signal source. A Schottky diode is electrically coupled in serial relation with the antenna, and in operation the signal is applied serially across the antenna and the diode in direct relation with electromagnetic waves transferred by the antenna. A bias current supply is also electrically coupled to the Schottky diode and is configurable to deliver a desired bias current across the current. The diode is responsive to the bias current to realize a desired diode impedance such that a desired impedance match/mis-match is provided between impedance of the diode and impedance of the antenna when the signal is applied across the antenna circuit, which selectively tunes the antenna circuit by imparting a desired power transfer therein. In one version, the antenna receives electromagnetic waves in the form of a radio frequency signal from a separate signal source which imparts a signal carried by the antenna to the antenna circuit such that the antenna circuit is powered by the signal. In another version, a separate signal source is provided in electrical communication with the antenna circuit such that the antenna circuit is powered by the signal source, preferably an oscillating source, which drives the antenna to produce transmitting electromagnetic waves.

Dual-band antenna for hand held portable telephones

Abstract: A novel planar dual-band inverted F-antenna for hand held portable telephones has been realised to operate at 0.9 and 1.8 GHz bands. The dual-band antenna is almost the same size as a conventional inverted F-antenna operating at 0.9 GHz, and has an isolation between bands of better than 17 dB.

Contrawound toroidal helical antenna

Abstract: An electrically small antenna is disclosed that is constructed from a generalized contrawound toroidal helix (1, 2) made from a single continuous conductor divided into two length portions each of which are substantially the same length and which have a generalized helical pattern. The helical pitch senses the two length portions are opposite to one another. The two length portions are insulated from one another and overlap one another on the surface of a generalized toroid. A signal is fed to the antenna at a port defined by the node locations (N1, N2) where the respective length portions join one another, or at a diametrically opposite point. A compact, broadband embodiment of the antenna is disclosed, as are other applications including a coaxial cavity resonator using the antenna as a feed element.

Antenna system for radio signals in at least two spaced-apart frequency bands

Abstract: In an antenna system for radio signals in at least two spaced-apart frequency bands above 200 MHz, a quadrifilar helical antenna having an elongate dielectric core with a relative dielectric constant greater than 5 has a conductive sleeve surrounding a proximal part of the core and a longitudinal feeder structure extending through the core to a connection with the helical antenna elements at a distal end of the core. The antenna is operated in an upper frequency band in which it exhibits a first mode of resonance characterized by current maxima at the connections of the helical elements to the feeder structure and at their junctions with the rim of the sleeve, and in a lower frequency band in which the antenna exhibits a second mode of resonance characterized by current minima in the region of the junctions of the helical elements and the sleeve rim. To permit dual mode operation, the antenna system includes an impedance-matching diplexer having filters coupled between a common port for the antenna and further ports for connection to radio signal processing equipment such as a GPS receiver and a mobile telephone operating in the two frequency bands. In the preferred embodiment, the filters and impedance matching elements are formed as microstrip elements on a single substrate.

Flat-top antenna apparatus including at least one mobile radio antenna and a GPS antenna

Abstract: The flat-topped antenna apparatus includes a GPS antenna, a mobile radio antenna, a common housing for the antennas mounted over a ground plane and coaxial cables (12,13,13a) acting as electrical supply lines for the antennas. The mobile radio antenna includes a metal sheet (6,6',6a) plane parallel to the ground plane and spaced at a distance (A,A') of 0.04 of an average operating wavelength of a mobile radio frequency band from the ground plane. The metal sheet is electrically connected at an input terminal (11) with an inner conductor (10) of one coaxial cable (13,13a) and also with the ground plane via a short circuit element (7,7a). The GPS antenna is above and rests on the mobile radio antenna and includes a dielectric plate (1,1a) provided with a metal layer (3) connected at an input terminal (4) with an inner conductor (10) of another (12) of the coaxial cables. The end points (14,15) of the outer conductors of the coaxial cables located near the respective input terminals (4,11) of both antennas are electrically connected to ground. At least one outer conductor is electrically connected to ground again at a connection point (16) which is located at a distance (d 1/4 ) of one quarter of the average operating wavelength from the grounded end point of the at least one outer conductor.

A single-layer dual-frequency rectangular microstrip patch antenna using a single probe feed

Abstract: A simple design of a dual-frequency microstrip antenna using a single rectangular patch and a single probe feed is described. Experimental results of the antenna resonating at frequencies of about 1.42 and 1.54 GHz are presented. Measurements are verified by the theoretical results obtained from full-wave solutions. © 1996 John Wiley & Sons, Inc.

Terahertz measurements of resonant planar antennas coupled to low‐temperature‐grown GaAs photomixers

Abstract: Resonant slot and dipole antennas coupled to low‐temperature‐grown GaAs photomixers have been fabricated and tested at terahertz operating frequencies. Enhanced output power is seen from the resonant structures compared to mixers coupled to broadband self‐complementary spiral antennas. Driving point impedances as high as 300 Ω are attained at the resonant frequencies. These devices will be useful as fixed frequency local oscillators for submillimeter heterodyne receivers.

First implementation of a superconducting integrated receiver at 450 GHz

Abstract: An integrated quasioptical receiver consisting of a planar double dipole antenna, superconductor‐insulator‐superconductor mixer and a superconducting local oscillator (LO) with matching circuits has been designed, fabricated and tested in the frequency range 360–490 GHz. A flux‐flow oscillator (FFO) based on unidirectional and viscous flow of magnetic vortexes in a long Josephson tunnel junction, is employed as a local oscillator. All components of the receiver are integrated on a 4 mm×4 mm×0.2 mm crystalline quartz substrate using a single Nb–AlOx–Nb trilayer. The lowest DSB noise temperature of 470–560 K has been achieved within a frequency range of 425–455 GHz.

Mobile device multiband antenna system

Abstract: A cellular communication system and mobile device in which the mobile device utilizes a single antenna to handle communications for two or more radios. Each radio is coupled to the antenna by an appropriate filter or the like which routes signals received in different frequency bands to the appropriate radio for processing. By using only one antenna to service multiple radios, problems associated with mutual coupling between multiple antennas can be eliminated. Also, use of a diversity antenna having left and right hand circularly polarized elements provides improved immunity to cross-polarization.

Antenna for reader/writer

Abstract: In an antenna 1a for reader/writer of an interrogator in a non-contact data carrier system comprising the interrogator and a transponder, the antenna for reader/writer of the interrogator comprises a transmitting antenna 2 for transmitting a signal to the transponder and a receiving antenna 3 for receiving a signal from the transponder, and the receiving antenna 3 is a loop coil located at a position where magnetic fields of opposite polarities are induced in the receiving antenna 3 by magnetic coupling between the receiving antenna 3 and the transmitting antenna 2 and where the magnetic fields of opposite polarities cancel out each other. Preferably, the transmitting antenna 2 is comprised of at least two loop coils 2a, 2b for generating magnetic fields of opposite polarities to each other.

Parasitic coplanar three-element dielectric resonator antenna subarray

Abstract: A slot-coupled rectangular dielectric resonator antenna in the parasitic coplanar configuration is investigated experimentally. The measured results for impedance and radiation patterns are presented for the three-element case. It is found that by using suitable choice of the dimensions and offset distance of each dielectric resonator, the impedance bandwidth can be as high as three times that of the single-element structure.

FDTD modeling of common-mode radiation from cables

Abstract: Radiation from cables attached to printed circuit boards and shielding enclosures is among the primary concerns in meeting FCC Class A and B limits. The finite-difference time-domain (FDTD) method can be employed to model radiation from printed circuit boards and shielding enclosures with complex geometries, but difficulties in modeling wires and cables of arbitrary radii are encountered. Modeling the wire by setting the axial component of the electric field to zero in the FDTD method results in an effective wire radius that is determined by the mesh discretization. Neglecting the wire radius in applications, such as electromagnetic interference (EMI) or printed circuit board modeling, may result in gross errors because near-field quantities are typically sensitive to wire thickness. Taflove et al. (1988) have developed a subcellular FDTD algorithm for modeling wires that has been shown to work well for plane wave scattering. The method uses a quasistatic field approximation to model wires with a well defined radius independent of the mesh dimensions. The wire model is reviewed and investigated for application to common-mode radiation from cables attached to printed circuit boards, where the source is often a noise voltage at the connector. Also investigated is energy coupling to attached cables through enclosure apertures resulting in common-mode radiation from the cable. The input impedance for a center-fed dipole antenna, as well as a monopole connected to a conducting half-sheet, is computed with FDTD methods and compared to moment method input impedance results. A simulation of a shielding enclosure with an attached cable demonstrates the utility of FDTD analysis in modeling common-mode radiation.

Portable RF antenna

Abstract: A small, collapsible, high-gain, dipole antenna and a method to make the antenna The present invention provides a collapsible half-wavelength dipole antenna for use in a portable device, the antenna having a fully collapsed position and a fully extended position The antenna includes a static dipole arm, and a movable dipole arm The movable dipole arm is capable of being moved to the fully collapsed position and the fully extended position The antenna also includes a balun feed assembly electrically coupled to the static dipole arm and to the movable dipole arm The antenna is capable of transmitting and receiving electrical signals in either the fully collapsed position or the fully extended position The balun feed assembly is fixed to the static dipole arm, and the movable dipole arm is movably coupled to the balun feed assembly According to specific embodiments, the antenna may include a static dipole arm positioned adjacent and parallel to the balun feed assembly to provide a folded dipole antenna when in the fully collapsed position In accordance with other embodiments, the movable dipole arm of the present antenna may be, for example, retracted or rotated into its collapsed position

Wideband, stacked double C-patch antenna having gap-coupled parasitic elements

Abstract: A stacked, shorted double C-patch antenna (100) has gap-coupled parasitic elements (102a, 106a, 102b, 106b) and one directly fed antenna element (104a). A second fed element (104b) is conductively fed from the directly fed element. The antenna has a truncated ground plane (108) and a bandwidth that is equal to or greater than approximately 70 MHz at a frequency of approximately 850 MHz. The directly fed antenna element is conductively coupled to a transmitter and to a receiver of a communications device, such as a cellular telephone.

High zenithal directivity from a dipole antenna on a photonic crystal

Abstract: A strip dipole on a (111)‐oriented face centered cubic photonic crystal is found to have a copolarized directivity and radiative gain of 9.1 and 7.2±1.4, respectively, along the zenith and at a frequency in the first stop band of 18.0 GHz. Under the same conditions, the maximum copolarized directivity and radiative gain were 10.0 and 8.1±1.6, respectively, in the H‐plane 5° down from the zenith. The zenithal results correspond to a 5.5‐times greater radiation intensity than displayed by the same dipole in free space. From power balance measurements, only 10% of this enhancement is attributed to superior power transfer between the generator and antenna. The remainder is associated with constructive interference between the primary antenna radiation and radiation reflected from the crystal.

Small, battery operated RF transmitter for portable audio devices for use with headphones with RF receiver

Abstract: A portable RF transmitter having an audio plug extending therefrom which mates with the earphone or output jack of an audio source such as a portable battery operated CD or tape player and having no external antenna The portable RF transmitter modulates audio signals from the audio source onto an FM carrier and transmits them to an FM receiver mounted on a headset worn by a user The RF transmitter uses its own ground circuit and the ground circuit of the audio source as two elements of a short dipole The two ground circuits are electrically isolated at RF by an RF choke but connected together at audio frequencies by the low impedance of the choke at audio The choke's leakage inductance also reduces the capacitive reactance of the dipole antenna for better power dissipation A transformer coupling the RF output to the dipole transforms the impedance of the dipole to a value closer to the output impedance of the RF transmitter