Showing papers on "Coaxial antenna published in 2003"

Printed double-T monopole antenna for 2.4/5.2 GHz dual-band WLAN operations

Abstract: A novel and simple printed dual-band double-T monopole antenna is proposed. The antenna comprises two stacked T-shaped monopoles of different sizes, which generate two separate resonant modes for the desired dual-band operation. The proposed antenna has a low profile and can easily be fed by using a 50 /spl Omega/ microstrip line. Prototypes of the proposed antenna designed for WLAN operations in the 2.4 and 5.2 GHz bands have been constructed and tested. Good radiation characteristics of the proposed antenna have been obtained. Effects of varying the monopole dimensions and the ground-plane size on the antenna performance have also been studied.

Aperiodic array antenna

Abstract: An antenna array that uses at least two passive antennas and one active antenna disposed above a ground plane, but electrically isolated from the ground plane, and a respective resonant strip positioned beneath each passive antenna. The passive antenna elements are positioned about the active element, and each of the at least two passive antenna elements is individually set to a reflective or a transmissive mode to change the characteristics of an input/output beam pattern of the antenna apparatus.

A low-profile planar monopole antenna for multiband operation of mobile handsets

Abstract: A novel planar monopole antenna is proposed. It has a very low profile (antenna height less than 0.04 times the operating wavelength in free space) and is capable of multiband operation. The proposed antenna has a planar rectangular radiating patch in which a folded slit is inserted at the patch's bottom edge. The folded slit separates the rectangular patch into two subpatches, one smaller inner subpatch encircled by the larger outer one. The proposed antenna is then operated with the inner subpatch resonating as a quarter-wavelength structure and the outer one resonating as both a quarter-wavelength and a half-wavelength structure. The proposed antenna, 12 mm high and 30 mm wide, has been constructed, and the obtained bandwidths cover the global system for mobile communication (890-960 MHz), digital communication system (1710-1880 MHz), personal communication system (1850-1990 MHz), and universal mobile telecommunication system (1920-2170 MHz) bands. Details of the proposed design and obtained experimental results are presented and discussed.

Aircraft phased array antenna structure including adjacently supported equipment

Abstract: An aircraft phased array antenna system has transmit and receive antenna structures externally mounted on the aircraft fuselage. Each antenna comprises a plurality of phased array elements and antenna power and support equipment. Aerodynamically shaping antenna structure to enclose an antenna element grid provides additional antenna structure volume, which is efficiently utilized by locating antenna support equipment within the antenna structure. To control signal attenuation a receive antenna internal converter converts receive frequency signals to L-band frequency signals for aircraft use, and a similar transmit antenna converter converts L-band frequency signals to transmit frequency signals, thus unconstraining antenna to internal aircraft equipment spacing. To reduce power loss and cabling weight, antenna operating power is first generated in the 28 to 270 volts DC range within the aircraft, and locally converted in each antenna to the 3 to 6 volt DC power to operate each antenna's phased array elements.

A reconfigurable slot antenna with switchable polarization

Abstract: A novel reconfigurable slot antenna architecture allowing polarization switching is presented. The antenna shape consists of a slot-ring with perturbations which are switched on and off using pin-diodes. Two antennas allowing switching either between linear and circular polarization or between two circular polarizations are demonstrated. The antenna architecture is interesting for commercial wireless applications because it is compatible with modern fabrication processes and can be realized on low cost dielectric materials.

A dual polarized aperture coupled circular patch antenna using a C-shaped coupling slot

Abstract: The design and development of a dual linearly polarized aperture coupled circular microstrip patch antenna at C-band are presented. The antenna uses a novel configuration of symmetric and asymmetric coupling slots. Variations in isolation between orthogonal feedlines and antenna axial ratio with the position of coupling slots are studied and broadband isolation and axial ratio are achieved. The prototype antenna yields 7.6 dBi peak gain, 70/spl deg/ 3-dB beam width, 25 dB cross-polarization levels and an isolation better than 28 dB between the two ports. With an external quadrature hybrid coupler connected to the two orthogonal feedlines, the antenna yields 3-dB axial ratio bandwidth of more than 30% at 5.8 GHz.

Analysis and Simulation of a 1-18-GHz broadband double-ridged horn antenna

Abstract: A 1-18-GHz broadband double-ridged horn antenna with coaxial input feed section is investigated. For the ridged horn antenna it is found that the radiation pattern, contrary to common belief, does not maintain a single main lobe in the direction of the horn axis over the full frequency range. Instead, at frequencies above 12 GHz, the main lobe in the radiation pattern starts to split into four large side lobes pointing in off-axis directions with a dip of up to 6 dB between them along the main axis. Although this type of horn is the preferred test antenna, which is in common use for over four decades, no explanation for this unwanted behavior was found in the open literature. To investigate this phenomenon in detail, a method of moments approach has been adopted to simulate the complete antenna system. The simulations are in good agreement with the measurements over the 1-18-GHz operational bandwidth and indicate that the use of this type of horn antenna in EMC applications remains questionable.

A broad-band CPW-fed strip-loaded square slot antenna

Abstract: A novel broadband design of a coplanar waveguide fed square slot antenna loaded with conducting strips is proposed and experimentally studied. The obtained results show that the impedance bandwidth, determined by 10-dB return loss, of the proposed slot antenna can be greater than 60%. The design considerations for achieving broad-band operation of the proposed slot antenna are described, and experimental results are presented.

Coplanar waveguide-fed square slot antenna for broadband circularly polarized radiation

Abstract: A new design of a broadband circularly polarized square slot antenna fed by a single coplanar waveguide (CPW) is proposed and experimentally studied. The proposed broadband circular polarization (CP) operation is achieved by protruding a T-shaped metallic strip from the ground plane toward the slot center and feeding the square slot antenna using a 50-/spl Omega/ CPW with a protruded signal strip at 90/spl deg/ to the T-shaped strip. Experimental results of constructed prototypes show that the obtained 3-dB and 1-dB axial-ratio bandwidths can reach as large as 18% and 13%, respectively. The proposed antenna also has a peak antenna gain of about 4 dBi, with gain variations less than 1 dBi for frequencies within the CP bandwidth.

Numerical analysis of stacked dielectric resonator antennas excited by a coaxial probe for wideband applications

Abstract: The objective of the present study is to improve the bandwidth of the dielectric resonator antenna (DRA) excited by a coaxial probe by using a stacked DRA configuration above an infinite ground plane. The DRA is axisymmetric and a coaxial probe is placed off the antenna axis to excite the HEM/sub 11/spl delta// mode in the DRA, resulting in a broadside radiation pattern. A surface integral equation formulation and the method of moments are used for the numerical analysis. The input impedance and the far field radiation patterns have been computed and the effects of different parameters on the antenna performance have been investigated. With the proper excitation and selection of the resonator parameters, a bandwidth of 35% has been achieved for the stacked DRA configuration based on a -10 dB reflection coefficient on a 50 /spl Omega/-transmission line. An equivalent circuit model is postulated to describe the dual-resonance behavior of the stacked antenna system.

Physical limitations of antenna

Abstract: A discussion of minimum possible antenna quality factor (Q) is first presented . Based on the spherical wave function theory, the maximum possible ratios of gain to Q for both directional antenna and omnidirectional antenna are examined and new upper limits for both cases have been obtained. Universally applicable numerical results and some related discussions are also included.

Low-cost broadband circularly polarized patch antenna

Abstract: A novel single-feed broadband circularly polarized patch antenna is proposed. The proposed antenna has a simple structure, consisting of a corner-truncated square radiating patch, an L-shaped ground plane, and a probe feed. Through a via hole in the vertical ground of the L-shaped ground plane, the radiating patch is easily excited by a probe feed oriented in the same plane as the patch, and circular polarization (CP) radiation over a wide frequency range (>10%) is achieved. Experimental results of a constructed prototype with the center operating frequency at about 2500 MHz showed that the antenna has an impedance bandwidth (1.5:1 VSWR) of about 30%, a 3-dB axial-ratio CP bandwidth of about 10.4%, and a gain level of 8.5 dBi or larger within the CP bandwidth. In addition to the low cost of the proposed antenna due to its simple structure, the obtained CP performance is among the best that have been reported for single-feed single-element patch antennas.

Numerical and experimental investigation of an ultrawideband ridged pyramidal horn antenna with curved launching plane for pulse radiation

Abstract: We report the numerical analysis and experimental characterization of an ultrawideband (UWB) antenna designed for radiating short microwave pulses. The antenna consists of a pyramidal horn, a ridge, and a curved launching plane terminated with resistors. The pyramidal horn is connected to the outer conductor of the coaxial feed and serves as the ground plane. The curved launching plane is connected to the central conductor of the coaxial feed. Detailed three-dimensional finite-difference time-domain (FDTD) simulations have been conducted to assist with the characterization of the antenna. FDTD results are compared with experimental data and are shown to be in good agreement. We demonstrate that the antenna exhibits a very low voltage standing wave ratio (/spl les/1.5) over a wide frequency range from 1 to 11 GHz and a very high fidelity (/spl ges/0.92). The spatial distribution of radiated energy is characterized both in the time domain, using transient field observations at various angles, as well as in the frequency domain, using single-frequency far-field radiation patterns. We conclude that this antenna offers high-fidelity transmission and reception of ultrashort microwave pulses with minimal distortion.

3-D FDTD design analysis of a 2.4-GHz polarization-diversity printed dipole antenna with integrated balun and polarization-switching circuit for WLAN and wireless communication applications

Abstract: Detailed numerical simulation, fabrication, and experimental measurements of a 2.4-GHz polarization-diversity printed dipole antenna are presented for wireless communication applications. Two orthogonal printed dipole antennas, each with a microstrip via-hole balun feeding structure, are combined and fabricated on an FR-4 printed-circuit-board substrate. A p-i-n diode circuit is used to switch and select the desired antenna polarization. In the antenna design simulation, a full-wave method of a three-dimensional finite-difference time-domain (FDTD) method is employed to analyze the entire structure of the printed antenna including the lumped elements of the polarization-selected p-i-n diode switching circuit. The Berenger perfectly matched layer absorbing-boundary condition is used for the FDTD computation. Numerical and measured results of antenna radiation characteristics, including input standing-wave ratio, radiation patterns, and polarization diversity are presented.

Seven-element ground skirt monopole ESPAR antenna design from a genetic algorithm and the finite element method

Abstract: The design of an optimized electronically steerable passive array radiator (ESPAR) antenna is presented. A genetic algorithm using a finite element based cost function optimized the antenna's structure and loading conditions for maximal main lobe gain in a single azimuth direction. Simulated gain results of 7.3 dBi at 2.4 GHz were attained along the antenna's elemental axis. The optimized antenna was fabricated and tested with the corresponding experimental gain better than 8 dBi. The 0.7 dB error between simulated and measured gain was constant for numerous structures and therefore did not affect the optimization. The optimized antenna reduced average main lobe elevation by 15.3/spl deg/ to just 9.7/spl deg/ above the horizontal.

Wide-band truncated tetrahedron dielectric resonator antenna excited by a coaxial probe

Abstract: A truncated tetrahedron dielectric resonator antenna is examined numerically and experimentally. The tetrahedron base is an equilateral triangular over a ground plane and excited by a coaxial probe to provide a broad side radiation pattern. Three different configurations are analyzed: the truncated tetrahedron when the wide base is attached to the ground plane, the narrow base attached to the ground plane, and the equitriangular cylinder. Results are verified experimentally and numerically. The tetrahedron with narrow base attached to the ground plane achieves wide-band performance for the impedance match and the radiation patterns of about 40%.

Wideband dual polarized base station antenna offering optimized horizontal beam radiation patterns and variable vertical beam tilt

Abstract: A dual polarized variable beam tilt antenna (10) having a plurality of offset element trays (12) each supporting pairs of dipole elements (14) to orient the dipole element pattern boresight at a downtilt. The maximum squint level of the antenna is a consistent downtilt off of boresight and which is at the midpoint of the antenna tilt range. The antenna provides a high roll-off radiation pattern through the use of Yagi dipole elements configured in this arrangement, having a beam front-to-side ratio exceeding 20 dB, a horizontal beam front-to-back ratio exceeding 40 dB, and is operable over an expanded frequency range.

Magnetically coupled antenna range extender

Abstract: A magnetically coupled antenna range extender structured to be interposed between an RF antenna and an electronic device. The antenna range extender is positioned between and proximate to one of the RF antenna and the electronic device, for extending the operating range over which information may be communicated and exchanged between the RF antenna and the electronic device.

Wearable microstrip antenna

Abstract: Microstrip antennas are being used as a representative antenna for mobile and satellite communication The microstrip antennas have features such as planarity and a relatively high gain (about 7 dBi) It is typical to fabricate them by using hard substrates However, these substrates are limited in shape and mounting placement for fixing such an antenna to clothing or hats Therefore, we created a flexible and light-weight antenna The antenna we built is composed of a flexible woven conductive fabric and felt Because of the construction, it can be easily sewn into clothing or hats It can be applied as a GPS antenna for monitoring the position of wandering aged, or as a terminal antenna for personal satellite communications In this paper, the structure of the antenna is described, and its characteristics are evaluated

Extendable planar diversity antenna

Abstract: The present invention is a retractable/extendable diversity antenna that provides the appropriate polarization in a horizontal orientation. The antenna structure is placed within a Type II PCMCIA PC card package and may be extended or retracted with one touch. The antenna structure is large enough to provide for the diversity antenna design and may optionally be housed within a PCMCIA Type II PC Card. At least one spring-loaded mechanism is used to extend the antenna structure beyond the PCMCIA PC Card package and to provide stability while the antenna structure is in the extended position. The diversity antenna configuration may consist of either two miniature, planar antenna modules or two etched printed circuit board contours that are spaced as far apart as possible with a minimum separation of a quarter wave length distance in order to provide mitigation to radio multipath fading effects. The antenna modules have orientations perpendicular to each other such that the polar nulls representative of their radiation patterns remain spatially orthogonal.

Antenna with a plurality of primary radiators

Abstract: PROBLEM TO BE SOLVED: To improve gain of antenna, by making the whole body compact and preventing interference of primary radiators arranged adjacently. SOLUTION: The antenna includes an electric wave convergence part 2 for converging an incident electric wave from different directions to a plurality of focal points, and a plurality of primary radiators 1 arranged at the plurality of the focal points of the electric wave convergence part 2. The primary radiator 1 has a dielectric antenna 4 and receives the electric wave focused on the focal point of the electric wave convergence part 2 by using the dielectric antenna 4.In addition, the dielectric antenna 4 is an eccentric dielectric antenna 4, of which a phase center of received electric wave is capable of shifting to a direction crossing with the propagation direction. The eccentric dielectric antenna 4 is arranged at a focal point of the electric wave convergence part and receives the electric wave converged at the focal point of the electric wave convergence part. COPYRIGHT: (C)2005,JPO&NCIPI

Antenna device, radio reception device, and radio transmission device

Abstract: There are provided an antenna deice, a signal reception device, and a signal transmission device utilizing an antenna element having a microstrip structure and coplanar structure and using a superconductive material. The antenna device, the signal reception device, and the signal transmission device realize improvement of a directivity gain, reduction of size, and reduction of power consumption. The antenna device includes: a planar antenna element; an adiabatic vessel having a radio window for transmitting electric waves, containing the planar antenna element, and insulating heat from outside; a waveguide arranged in the adiabatic vessel between the radio window and the antenna pattern formation plane of the planar antenna element; and cooling means for cooling the planar antenna element. The waveguide has a shape and dimensions which intensify the directivity of the planar antenna element and a superconductive film is used for the antenna pattern of the planar antenna element.

A coaxial antenna with miniaturized choke for minimally invasive interstitial heating

Abstract: We present a new coaxial antenna for microwave interstitial coagulative therapy, working at 2450 MHz and endowed with a miniaturized sleeve choke in order to reduce back heating effects and make the system response less dependent on the antenna insertion depth into the tissue; the way the choke is implemented makes the overall transversal size minimum and allows small adjustments of the choke section length even during operation. We describe the main technical features of the antenna and show experimental results clearly proving the choke effectiveness. Numerical simulations well agree with experimental data, confirming the suitability of the proposed device for minimally invasive medical applications.

Microwave antenna having a curved configuration

Abstract: A microwave antenna having a curved configuration is described herein. The antenna portion is formed into various shapes whereby the antenna substantially encloses, by a partial or complete loop or enclosure, at least a majority of the tissue to be irradiated. When microwave energy is delivered through the antenna, the curved configuration forms an ablation field or region defined by the curved antenna and any tissue enclosed within the ablation region becomes irradiated by the microwave energy. The microwave antenna is deployed through one of several methods, and multiple curved antennas can be used in conjunction with one another. Moreover, RF energy can also be used at the distal tip of the antenna to provide a cutting tip for the antenna during deployment in tissue.

Folded dipole antenna near metal plate

Abstract: The paper presents the effects on antenna parameters when an antenna is placed horizontally near a metal plate. The plate has finite size and rectangular shape. A folded dipole antenna is used and it is placed symmetrically above the plate. The FEM (finite element method) is used to simulate the dependency of antenna parameters on the size of the plate and the distance between the plate and the antenna. The presence of the metal plate, even a small one if it is at the right distance, causes very big changes in the behaviour of the antenna. The bigger the plate, especially in width, the sharper and narrower are the lobes of the radiation pattern. The antenna height defines how many lobes the radiation pattern has. A number of the antenna parameters, including impedance, directivity and front-to-back ratio, change periodically as the antenna height is increased. The resonant frequency of the antenna also changes under the influence of the metal plate.

Monopulse radar system

Abstract: To realize a monopulse radar system wherein the velocity of a mobile body, distance between an obstacle and the mobile body and relative velocity can be detected and simultaneously, the direction of the obstacle can be detected, in a monopulse radar system wherein an azimuth is detected depending upon amplitude difference or phase difference between signals respectively received by plural receiving antennas, an array antenna composed of plural antenna elements is used for each transmitting antenna and each receiving antenna, at least one of the transmitting antenna and the receiving antenna is provided with an antenna switch for switching an antenna beam shape to a short angle/long distance or a wide angle/short distance and a switch control device that controls the switching of the antenna switch is provided

Wide band four-port butler matrix for switched multibeam antenna arrays

Abstract: This paper presents the design and realization of a wide band four-port microstrip matrix to feed a switched-beam antenna array for wireless applications at 1.9 GHz. The objective of this investigation is to develop an antenna-array feeding network based on Butler with a large bandwidth in order to cover the PCS band: 1900 MHZ to 2200 MHZ. In order to meet these requirements, wide band microwave components such as hybrids and crossovers were designed and used to Butler proposed matrix. The Butler matrix is used as a beamforming network that allows to produce orthogonal beams that can be steered in different directions. To examine the performance of the proposed matrix, simulated and experimental results is presented and discussed.

Fixed-frequency beam-steerable leaky-wave microstrip antenna

Abstract: A fixed frequency continuously beam-steerable leaky-wave antenna in microstrip is disclosed. The antenna's radiating strips are loaded with identical shunt-mounted variable-reactance elements, resulting in low reverse-bias-voltage requirements. By varying the reverse-bias voltage across the variable-reactance elements, the main beam of the antenna may be scanned continuously at fixed frequency. The antenna may consist of an array of radiating strips, wherein each strip includes a variable-reactance element. Changing the element's reactance value has a similar effect as changing the length of the radiating strips. This is accompanied by a change in the phase velocity of the electromagnetic wave traveling along the antenna, and results in continuous fixed-frequency main-beam steering. Alternatively, the antenna may consist of two long radiating strips separated by a small gap, wherein identical variable-reactance elements are mounted in shunt across the gap at regular intervals. A continuous change in the reactance value has a similar effect as changing continuously the width of the radiating strips. This results in a continuous change in the phase velocity of the electromagnetic wave traveling along the antenna, thereby achieving continuous fixed-frequency main-beam steering.

Low cost multiple pattern antenna for use with multiple receiver systems

Abstract: An antenna assembly includes at least two active or main radiating omni-directional antenna elements arranged with at least one beam control or passive antenna element used as a reflector. The beam control antenna element(s) may have multiple reactance elements that can electrically terminate it to adjust the input or output beam pattern(s) produced by the combination of the active antenna elements and the beam control antenna element(s). More specifically, the beam control antenna element(s) may be coupled to different terminating reactances to change beam characteristics, such as the directivity and angular beamwidth. Processing may be employed to select which terminating reactance to use. Consequently, the radiator pattern of the antenna can be more easily directed towards a specific target receiver/transmitter, reduce signal-to-noise interference levels, and/or increase gain by using Radio Frequency (RF), Intermediate Frequency (IF), or baseband processing. A Multiple-Input, Multiple-Output (MIMO) processing technique may be employed to operate the antenna assembly with simultaneous beam patterns.

Broad-band suspended probe-fed plate antenna with low cross-polarization levels

Abstract: A new feeding scheme for enhancing the radiation performance of a suspended plate antenna with a broad bandwidth is presented experimentally. By means of a probe-fed half-wavelength strip, the high cross-polarization levels of the suspended plate antenna are suppressed effectively, which result mainly from the undesired excitation of higher-order modes. Measurements on the antenna with the proposed feeding structure have demonstrated the good performances with a high ratio of co- to cross-polarization levels and stable radiation patterns across a 20% bandwidth for VSWR/spl les/2 : 1.