Showing papers on "Coaxial antenna published in 1993"

Novel ultrawide-bandwidth Vivaldi antenna with low crosspolarisation

Abstract: The conventional Vivaldi antenna typically has a bandwidth of less than 3:1, limited by the feed line to radiating slot transition. The antipodal Vivaldi antenna removes this limitation but gives very high crosspolarisation which is undesirable for phased array applications. The Letter describes a new balanced antipodal Vivaldi antenna that retains the wide bandwidth characteristics while reducing the crosspolarisation by 15dB across an 18:1 band. Measurements are presented that compare the performance of existing antenna structures with this novel antenna element.

Dual polarized dual band antenna

Abstract: An antenna system is described including a reflector antenna, responsive to radio frequency signals at a first frequency, having a first reflector surface, a second reflector surface and a Cassegrain feed. The antenna system further includes an array antenna having a plurality of antenna elements responsive to radio frequency signals having a second different frequency, wherein a center element is in a common location with the feed of the reflector antenna. With such an arrangement, an improved dual band antenna system is provided. By providing the center element of the array antenna in a common location with the feed of the reflector antenna, a dual band radio frequency antenna system is provided which is more compact with improved radiation characteristics than known similar configured antennas.

A curl antenna

Abstract: A radiation element, designated as a curl antenna, is proposed for a circularly polarized antenna. The radiation characteristics of the curl are numerically analyzed. The gain is approximately 8.4 dB, and the 3-dB axial ratio criterion is 6.7%. Two aspects of curl array antennas are also presented: a decoupling factor between two curls and a circular array antenna consisting of 168 curls. Calculations show how the decoupling factor depends on the relative rotation angle of the two curls. The 168-curl array antenna shows a high aperture efficiency of 95%. >

Gap raidated antenna

Abstract: An antenna for broadcast and reception of electromagnetic waves in which all or a portion of the radiating structure is formed from coaxial cable or a functional equivalent thereof in which an annular opening exists, allowing alternating electrical current to propagate onto the outer surface of said radiative structure, thereby generating electromagnetic radiation.

Electric-monopole antenna using a dielectric ring resonator

Abstract: A dielectric ring resonator antenna structure which radiates like an electric monopole is reported. The use of high er resonator material leads to small antenna height. Experiments show that the proposed antenna configuration is potentially useful for constructing small and compact ‘electric-monopole’ antennas.

Folded dipole microstrip antenna

Abstract: A folded dipole microstrip antenna is disclosed herein. The microstrip antenna includes a dielectric substrate for defining a first mounting surface and a second mounting surface substantially parallel thereto. A folded dipole radiative element is mounted on the second mounting surface. The microstrip antenna further includes a microstrip feed line, mounted on the first surface, for exciting the radiative element in response to an excitation signal. In a preferred implementation of the microstrip antenna an excitation signal is applied to the microstrip feed line through a coaxial cable. In such a preferred implementation the folded dipole radiative element includes a continuous dipole arm arranged parallel to first and second dipole arm segments separated by an excitation gap. The feed element is mounted in alignment with the excitation gap and is electrically connected to the continuous dipole arm. The antenna may additionally include a ground plane reflector separated from the folded dipole radiative element by a dielectric spacer for projecting, in a predetermined direction, electromagnetic energy radiated by the folded dipole radiative element. The thickness of the dielectric spacer between the ground plane reflector and the folded dipole radiative element is selected such that the impedance presented by the antenna to the coaxial cable is approximately fifty ohms.

Closed slot antenna having outer and inner magnetic loops

Abstract: An RF identification system having an interrogator operable to send RF interrogations to a transponder and to receive RF responses from the transponder. The interrogator is in electrical communication with a closed slot antenna. The closed slot antenna is formed by an an outer visual magnetic loop and an inner visual magnetic loop such that the antenna has a superior magnetic field when compared to a balanced double loop antenna with an equal area and a superior far-field noise suppression when compared to the single loop antenna. The antenna receives said RF responses from the transponder and provides said RF responses to said interrogator. Other devices, systems and methods are also disclosed.

An improved solution for integrated array optics in quasi-optical mm and submm receivers: the hybrid antenna

Abstract: A dielectric lens antenna that is a special case of an extended hemispherical dielectric lens and is operated in the diffraction-limited regime is considered. The dielectric lens antenna is fed by a planar antenna that is mounted on the flat side of the dielectric lens antenna, using it as a substrate, and the combination is termed a hybrid antenna. Beam pattern and aperture efficiency measurements were made at millimeter and submillimeter wavelengths as a function of the extension of the hemispherical lens and of lens size. An optimum extension distance for which excellent beam patterns and simultaneously high aperture efficiencies can be achieved is found experimentally and numerically. At 115 GHz the aperture efficiency was measured to be (76+or-6)% for a diffraction-limited beam with sidelobes below -17 dB. Results for a single hybrid antenna with an integrated superconductor-insulator-superconductor (SIS) detector and a broadband matching structure at submillimeter wavelengths are presented. The hybrid antenna is space efficient in an array due to its high aperture efficiency, and is easily mass produced, thus being well suited for focal plane heterodyne receiver arrays. >

A numerical study of a dielectric disk antenna above grounded dielectric substrate

Abstract: An antenna made of a dielectric disk with a high permittivity mounted on top of a grounded dielectric substrate of low permittivity is analyzed. A numerical procedure based on surface integral equations, derived from the equivalence principle, is used to compute the natural resonant frequencies for the HEM/sub 11/ mode from which the radiation Q factor of the antenna is obtained. Then the radiation pattern of the antenna, operating at the resonant frequency evaluated previously, is computed with an electric dipole excitation located within the dielectric substrate under the dielectric disk. The effect of various parameters on the radiation characteristics of the antenna is studied, and presented in the form of diagrams. The low values of the radiation Q, combined with the high values of the dielectric Q and conductor Q, indicate that this antenna promises to be more efficient then the microstrip antenna. >

Optimization of a conical antenna for pulse radiation: an efficient design using resistive loading

Abstract: The conical monopole antenna with a section of continuous resistive loading is considered as a radiator for temporally short, broad-bandwidth pulses. The geometrical details of the coaxial feed and the resistive loading are varied to optimize this structure for pulse radiation. Compared with the perfectly conducting cone, the optimized resistive cone radiates a better reproduction of the pulse excitation with no loss in amplitude, and has internal reflections that are much smaller in amplitude. Graphical displays of the field surrounding the antenna are used to give insight into the physical processes for transient radiation from this antenna. Experimental models were constructed to verify the optimization and demonstrate the practicality of the design. Measurements of both the reflected voltage in the feed line and the time-varying radiated field are in excellent agreement with the theoretical calculations. >

A half-split cylindrical dielectric resonator antenna using slot-coupling

Abstract: A half-split cylindrical dielectric resonator placed on a metallic plane and excited in its magnetic dipole mode is a potentially useful antenna element. The use of a microstrip line-slot feed scheme for exciting this antenna is reported. Experimental results show that the antenna displays the anticipated radiation pattern and it has a high operating frequency bandwidth (about 10%). The overall antenna configuration can be easily integrated with MICs. >

Flat plate antenna module

Abstract: An antenna module for use a non-conductive cab of a motor vehicle includes a dielectric substrate and one or more antenna loops arranged on the substrate. The substrate is adapted to be installed between the headliner of a cab and the dielectric roof. The module may include a CB antenna loop, an AM/FM antenna loop, a cellular mobile telephone antenna loop, and a global positioning system antenna, without the need for any antenna structure external to the cab. The antennae are arranged on the module in a nested configuration. A CB antenna, provided with loading coils, forms an outer loop. An AM/FM antenna loop, including a capacitor yielding a substantially short circuit connection in the FM frequency range, forms a FM frequency antenna loop and an AM frequency dipole, within the CB loop. A multiloop array cellular telephone antenna is arranged within the AM/FM loop. A standard crossed dipole GPS antenna is positioned in an area between the CB loop and the AM/FM loop near one corner of the substrate. Coaxial antenna feedlines connected to the various antennae are routed through cab support posts to associated electronic circuitry in the cab.

Active transmit phased array antenna.

Abstract: An active transmit phased array antenna system for generating multiple independent simultaneous antenna beams to illuminate desired regions while not illuminating other regions. The size shape of the regions is a function of the size and number of elements populating the array and the number of beams is a function of the number of beam forming networks feeding the array. All the elements of the array are operated at the same amplitude level and beam shapes and directions are determined by the phase settings. The active transmit phased array antenna includes a plurality of antenna elements disposed in a hexiform configuration. Each antenna element is identical and includes a radiating horn capable of radiating in each of two orthogonal polarizations. The horn is fed by a multi-pole bandpass filter means whose function is to pass energy in the desired band and reject energy at other frequencies. The filter means is coupled into an air dielectric cavity mounted on substrate. The air dielectric cavity contains highly efficient monolithic amplifiers which excite orthogonal microwave energy in a push-pull configuration by probes in combination with amplifiers placed such that they drive the cavity at relative positions 180 degrees apart. Phase shift means and attenuator means in the substrate are connected to the amplifiers in the cavity to determine beam and direction and for maintaining the signal amplitudes from each of the antenna elements at an equal level.

Input impedance of coaxially fed rectangular microstrip antenna on electrically thick substrate

Abstract: A full-wave spectral domain analysis has been used to obtain input-impedance results for a probe-fed rectangular-patch antenna, modeling the source as a magnetic-current frill. Multiple modes are used in the probe surface current to account for axial and azimuthal variations. It is established that maximum resistance is dependent on the substrate loss tangent. The axial variation of the probe current must be taken into account for substrate thicknesses greater than about 0.02 wavelengths.

Panel antenna having groups of dipoles fed with insertable delay lines for electrical beam tilting and a mechanically tiltable ground plane

Abstract: A panel antenna suitable for use in cellular communication applications provided with means for mechanically and electrically adjusting the tilt of the antenna beam. Electrical down tilt being achieved by varying the length of a first feed line to a group of dipole pairs. Mechanical down tilting of the antenna beam being achieved by tilting the antenna ground plane and dipole driver assembly with respect to a housing.

Three-wave antenna for vehicles

Abstract: A three-wave antenna for vehicles which includes a monopole antenna element which has an electrical length of approximately 1/4 of the wavelength in the FM broadcast band along with a double sleeve used to prevent current flow and with a second double sleeve used for phase adjustment that are installed coaxially with the antenna element. The positional relationships between the inner and outer cylinders of each one of the first and second double sleeves relative to the antenna element are respectively specified. In addition, an antenna attachment which has a capacitive reactance and is installed at the base of the antenna element so that it cancels the inductive reactance of the antenna and causes the impedance of the antenna to approach a prescribed value is employed together with a wave splitter which includes a high pass filter that has a double tuning function with respect to the inductive reactance and the capacitive reactance and a low pass filter that separates the AM/FM broadcast band signals from the telephone band.

Quasi-optical planar arrays with FETs and slots

Abstract: This work describes the design concept and experimental results for prototypes of two-dimensional quasi-optical power-combining arrays. Several different quasi-optical circuits were used to obtain the fundamental data for this study. How to incorporate the antenna input impedance into the active antenna circuit and how to analyze the strong coupling condition with two operating modes are addressed using large-signal analysis. Several circuit configurations are demonstrated, including a single active antenna operating at 9.3 and 24.0 GHz, a six-element linear power-combining array operating at 15.6 GHz, and four-element and sixteen-element two-dimensional power combining arrays operating at 10.4 and 7.8 GHz. Important characteristics such as antenna patterns and tuning ranges are discussed. The prospects for a two-dimensional monolithic quasi-optical power-combining array are discussed. >

Hybrid antenna including a dielectric lens and planar feed

Abstract: A hybrid antenna including a dielectric lens-antenna in the shape of an extended hemispherical dielectric lens than is operated in the diffraction limited regime. The dielectric lens-antenna is fed by a planar-structure antenna. The planar antenna is mounted on the flat side of the dielectric lens-antenna, using it as a substrate. An optimum extension distance is found experimentally and numerically for which excellent beam patterns and simultaneously high aperture efficiencies can be achieved. The hybrid antenna is diffraction limited, space efficient in an array due to its high aperture efficiency, and is easily mass produced, thus being well suited for focal place receiver arrays.

Crossed-slot antenna having infinite balun feed means

Abstract: A crossed-slot antenna having a reduced number of feed components to achieve circular polarization. The present invention provides a crossed-slot antenna capable of transceiving circularly polarized radiation and having a feed network comprising a ninety degree hybrid and at least one infinite balun. In one embodiment, a transmission line is used to feed a pair of antenna patch elements, one of which acts as a local ground plane for the microstrip line, thereby defining an infinite balun. The transmission line may comprise a microstrip line, the inner conductor of a coaxial cable, or a coplanar waveguide.

Active antenna near field calibration method

Abstract: In a method of calibrating an active antenna the active elements of a transfer function matrix are measured using a near field probe for each radiating source of the antenna. The probe is placed in front of each source in succession and each source is excited in turn with the opposite phase and with all the other sources of the array excited normally. In the case of linear superposition of radiated fields, the measurements obtained by this method yield the elements of the transfer function matrix directly. This allows for phase and amplitude errors due to the components of the active antenna and for the effects of coupling between adjacent sources which modify the theoretical characteristics of the antenna. In the non-linear case the measurements are repeated and the matrix is obtained by iteration based on a comparison of the theoretical values used to control the antenna and the measured fields actually obtained. Measurements carried out on individual active modules prior to assembly of the antenna can be used in one variant of the method.

Antenna assembly for a portable transceiver

Abstract: An antenna assembly for use with a portable transceiver provides improved communication between the portable transceiver and a base station. A novel antenna assembly is created wherein the radiating portion is elevated above the handset by combining a half wavelength sleeve dipole antenna with a coaxial line section followed by a quarter wavelength choke. Such a configuration reduces the antenna-housing interaction. The quarter wavelength choke prevents the coaxial transmission line from radiating RF energy, and therefore limits the radiation to the sleeve dipole portion of the antenna assembly.

Diversity glass antenna for an automobile

Abstract: A diversity glass antenna for an automobile, wherein a dipole antenna is provided on a glass plate of a window of an automobile, a single pole antenna is provided at a part other than the glass plate and a stronger one of receiving signals of the dipole antenna and the single pole antenna is selected and employed, or, a diversity glass antenna for an automobile, wherein a single pole antenna is provided on a glass plate of a window of an automobile, a dipole antenna is provided at a part other than the glass plate and a stronger one of receiving signals of the dipole antenna and the single pole antenna is selected and employed.

Steerable coaxial antenna systems for cardiac ablation

Abstract: A steerable antenna assembly (14) employs a coaxial cable having a proximal region (50) for connection to a source of energy and a distal region (16) for propagating the energy. The coaxial cable also has an intermediate region (32) between the distal and proximal regions that has a greater degree of flexibility than the proximal region. A steering mechanism (10) is connected directly to the intermediate region (32) of the coaxial cable for bending the intermediate region (32) and, with it, the distal energy propagation region of the coaxial cable relative to its proximal region.

Electromagnetic detection system

Abstract: An electromagnetic detection system comprising at least one source circuit and at least one source circuit-controlled antenna configuration, which comprises two loop antenna coils, substantially located in one plane or in closely spaced parallel planes, for generating a detection field in a detection zone, and a plurality of responders, provided with a loop antenna coil, detectable in the detection zone by means of the detection field, wherein one loop antenna coil of the antenna configuration is part of a series resonance circuit, and that the other loop antenna coil is part of a parallel resonance circuit, the series and parallel resonance circuits having the same resonance frequency and being interconnected to form a combined antenna network connected to the source circuit, and the series and parallel resonance circuits being dimensioned such that the frequency-dependent parts of the impedances substantially compensate each other, so that the combined antenna network has a substantially frequency-independent impedance.

Input impedance of a hemispherical dielectric resonator antenna excited by a coaxial probe

Abstract: A more rigorous model of the probe-fed hemispherical antenna than that of K W Leung et al (1991) is considered This model accounts for all possible azimuthal modes that can be excited by this structure The input impedance is computed for a dielectric sphere antenna of radius a=254cm, /spl epsi//sub r1/=89, and loss tangent 00038 >

Analysis of spherical annular microstrip antennas

Abstract: The spherical annular microstrip antenna is analyzed. The antenna is excited by a coaxial line. The general transmission line model (GTLM) is used to compute the input impedance. The radiating TM/sub 12/ mode is considered because of its wide band. The effect of the other radiating modes and the nonradiating modes on the TM/sub 12/ mode is investigated. The effect of different parameters on the input impedance is considered. The radiation patterns are computed using the method of moments. >

A folded slot antenna for planar quasi-optical mixer applications

Abstract: The simple uniplanar quasi-optical mixer uses the effect of orthogonal modes in the folded slot antenna fed by slotline and coplanar waveguide on opposite sides. The input impedance of the antenna is analyzed with the space domain integral equation technique. Experiments at 11 GHz have demonstrated antenna and mixer operation. The antenna shows reasonable radiating properties. By taking advantage of even and odd modes in the antenna, balanced mixing can be achieved with good conversion loss. >

Resonance and radiation of a superstrate-loaded spherical-circular microstrip patch antenna

Abstract: The effects of the dielectric superstrate cover on the resonance and radiation problems of a spherical-circular microstrip patch antenna are studied, using the Green's function formulation in the spectral domain and the Galerkin moment method calculation. Numerical results for the resonant frequency, half-power bandwidth, and radiation pattern of the superstrate-loaded antenna are presented. The effects of curvature on these characteristics are also shown. >

Wideband antenna arrangement

Abstract: A compact antenna arrangement for a portable transceiver in a wideband cellular radio system, comprises first and second antenna coils (3,4) tuned respectively to the transmit and receive frequencies and coupled respectively to the transmit and receive sections of the transceiver. The two antenna coils are provided in a common housing (10) external to the main housing (1) of the telephone and are disposed on a common axis. In one embodiment the antenna coils are arranged in-line (see Fig. 1). Alternatively, the antenna coils may be disposed concentrically, one within the other (see Fig.2); or they may be interwound (see Fig.3).

Antenna arrangement with reduced coupling between transmit antenna and receive antenna

Abstract: An antenna arrangement in which a first antenna means is arranged to define a null contour adjacent the first antenna means and at which the magnetic flux from the first antenna means is substantially a null and in which a second antenna means is arranged to substantially follow the null contour.