Showing papers on "Reflective array antenna published in 1999"

A method for designing broad-band microstrip antennas in multilayered planar structures

Abstract: The narrow bandwidth of a microstrip antenna is one of the important features that restrict its wide usage. A simple and practical method for the design of broad-band microstrip antennas is presented in this paper. Utilizing this design technique, several two-layer microstrip antennas have been proposed. To confirm the applicability of the method for the designs of antennas at L-band, experiments have been carried out. The measured results show that the proposed antennas have a bandwidth of up to 25.7%. Also, the method proposed in this paper is applicable to the design of other types of multilayered planar antennas.

Beamformer architectures for active phased-array radar antennas

Abstract: In active phased-array antennas, the transmit and receive functions are distributed at the antenna aperture using transmit and receive (T/R) modules. The use of T/R modules provides a significant improvement in antenna performance and flexibility in the choice of array architectures. We present a review of various beamformer architectures for active phased-array antennas. This review is limited to corporate-fed active phased-array antennas for radar applications. Beamformer architectures for narrow and wide bandwidth arrays, including the choice of applying an amplitude taper in the T/R module or beamformer network are discussed. Beamformer architectures that increase antenna reliability are also presented.

Integrated lens antennas for submillimetre-wave applications

Abstract: • A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers.

Near-field alignment of phased-array antennas

Abstract: This paper describes the algorithms and equipment used to apply near-field scanning techniques to the phase alignment of phased-array antennas. This procedure achieves a level of precision not previously available. The electronic scanning property of the antenna is used to bring different sections of the antenna spectrum within range of the near-field scanning process. These partial spectra are then merged to define the entire spectrum of the antenna. This process provides the resolution needed to determine the excitation at individual elements by the inverse Fourier transformation operation. The process described here has been used in the production of a very large number of phased-array antennas currently in service.

Dual-band microstrip antenna array

Abstract: A dual-band antenna array (50) for use in a base station for mobile telephone communications consists of a first linear array of microstrip or patch antennas (52) for use over the GSM band and a second linear array of crossed dipoles (56) for use over the PCN band. The PCN antennas are at half the spacings of the GSM antennas. Alternate ones of the PCN crossed dipole antennas are located above respective GSM patch antennas, and a conductive plate or sheet (66) between them functions both as a parasitic element for the microstrip antenna and as a reflector for the crossed dipole antenna.

Adaptive array device

Abstract: PROBLEM TO BE SOLVED: To provide an adaptive array device using plural waves with high efficiency according to a situation, and for efficiently housing a number of mobile units. SOLUTION: A first pattern calculating part 6 forms an array antenna pattern constituted of all antennas, and second and third pattern calculating parts 7 and 8 form in-group array antenna patterns constituted of antennas respectively for the group of antennas 10a-40a and the group of antennas 50a-80a by using different frequencies. A control part 3 switches the operations of the first pattern calculating part 6 and the second and third pattern calculating parts 7 and 8.

FASANT: past computer tool for the analysis of on-board antennas

Abstract: FASANT is a computer tool for the analysis of antennas on-board satellites, ships, aircraft, and other complex bodies. The structure under analysis, which can be metallic or dielectric (with and/or without losses), must be modeled by plane and/or curved surfaces. The geometrical input files are in DXF format, and can be generated by the most commonly used computer-aided geometrical-design (CAGD) tools. The code can also be applied to the analysis of arrays and arbitrarily shaped reflectors. The kernel of the code is based on the uniform theory of diffraction (UTD). Special algorithms have been developed to speed up the ray-tracing computation for both flat and curved surfaces. FASANT can obtain far-field patterns, field levels at points near the structure, can calculate the mutual coupling between antennas or between array elements, and can show each ray-tracing mechanism.

A 4 watt Ka-band quasi-optical amplifier

Abstract: This paper reports on demonstrated results for a 4 W, 16 dB gain Ka-band Quasi-Optical (QO) amplifier. This amplifier consists of a 13 element two-sided active array with a hard-horn feed. Excess heat is removed via a metal carrier integrated into the array. Each unit-cell consists of patch antennas, cascaded MMIC amplifiers and a unique through-thick-plate coupler. Performance and construction details are discussed. Preliminary results from a 45 element design are also included.

Design of TEM horn antennas for impulse radar

Abstract: As it is well known, TEM horns are antennas that can achieve wideband characteristics over multiple decades. This special characteristic of these antennas makes them really attractive for wideband radar/communication systems, where short time-domain pulses of a very wide frequency range are employed. Although these antennas have been investigated by a number of researchers over the last 25 years, as far as we known, there is very limited analysis and design guidelines available. In this paper, the TEM horn antenna has been investigated using the multiple quarter-wavelength transformer technique, which can be served as a design guideline. Antennas have been designed, made and tested. Good measurement results have demonstrated the usefulness of this technique.

Enhanced impulse radar system

Abstract: An impulse radar system useful, for instance, for ground penetration provides three dimensional images of targets. The radar system includes an antenna array with an arrangement of elements that is irregular so that the spacing between elements is different, thereby minimizing redundancy of path geometry between the array elements and the target. This feature reduces unwanted array sidelobes. The radar system incorporates circuitry which permits the utilization of each array element as either a transmitter or receiver antenna element. This dual utilization increases the effective number of elements in the antenna array, providing increased gain and system resolution. The radar system receiver utilizes multiple antenna array receiver elements, each of which is connected sequentially, through a solid state switch, to a single analog to digital converter, thereby providing a digitized signal for processing and display. This arrangement requires only a single analog to digital converter, thereby reducing size, cost, and errors due to analog to digital converter non-linearities.

Leaky‐Wave Antennas

Abstract: The sections in this article are 1 Distinctive Features And Applications 2 Operation Principles 3 Design Techniques 4 Overview Of Specific Structures 5 Practical Considerations And Measurements

Dual near-field focused antenna array

Abstract: A communication system for transferring data through the air over a relatively short fixed distance comprising a transmitting antenna which comprises a leaky coaxial cable for radiating electromagnetic energy modulated with data to be transferred; and a plurality of non-linear fixed beam array antennas for receiving the modulated electromagnetic energy from the leaky coaxial cable. The plurality of fixed beam array antennas are juxtaposed with the transmitting antenna such that the transmitting antenna extends at least partially through the near-field regions of the plurality of fixed beam array antennas. The communication system also comprises a selection means which determines which radio frequency output from the plurality of non-linear fixed beam array antennas exhibits the greatest radio frequency power and outputs that particular radio frequency output to a receiver. Also described is a method of increasing the performance of an antenna system, which comprises the steps of inputting radio frequency signals from a plurality of antennas, selecting that radio frequency signal which comprises the greatest radio frequency power, and outputting the radio frequency signal comprising the greatest radio frequency power.

Miniature phased array antenna system

Abstract: A miniature phased array antenna system employs a substrate having a high dielectric constant. A plurality of antenna elements are located on a surface of the substrate, and a superstrate having a high dielectric constant covers the antenna elements. The dielectric constant, thickness, and shape of the superstrate enable it to act as a dielectric lens for controlling the phase relationship of a signal received by the antenna elements. The design of the superstrate dielectric lens permits a reduction in the physical spacing between the antenna elements while maintaining spatial diversity in phase between signals arriving from different directions. Thus, the antenna array may be significantly smaller than conventional phased array antennas while maintaining a similar phase relationship to that achieved using conventional phased array antennas. Electronic circuitry coupled to each of the plurality of antenna elements applies complex weights to received signals prior to a summation thereof in order to reconstruct a desired signal and to deconstruct an undesired signal. SAW filters employed in the electronic circuitry are temperature controlled to maintain group-delay and phase-offset stability.

Recalculating linear array antennas to compensate for failed elements while maintaining fixed nulls

Abstract: Given the failure of one or more elements of an array antenna designed to produce a radiation pattern including nulls in arbitrarily fixed directions, a pattern with the desired side lobe level and nulls can often be recovered by modifying the excitations of the non-defective elements. The modified excitations can be calculated by simulated annealing using an appropriate cost function.

Adjustable-tilt antenna

Abstract: The present invention lies in the field of antennas for land cellular radio communications networks, and it relates to a remote control method for adjusting the tilt of the radiation pattern relative to the horizontal of the antennas of a base station. The invention also relates to an antenna fitted with means for adjusting its tilt and to a system for remote control of the tilt. The technical field of the invention is active antennas (also known as “smart” antennas or as “adaptive” antennas) for networks for communicating with mobile telecommunications terminals. According to the invention, an antenna for a land cellular telecommunications network, the antenna comprises radiating elements and feeder means for feeding said radiating elements with radio frequency signals; said feeder means include electronic phase shifter means for obtaining phase shifts between said signals so as to enable the tilt of the radiation pattern in a vertical plane to be adjusted remotely.

Cross-mesh array antennas for dual LP and CP waves

Abstract: A grid array antenna acts as a radiation element of linear polarization. This paper presents the radiation characteristics of two cross-mesh array antennas each composed of two grid array antennas. It is found that the cross-mesh can radiate a dual linearly polarized (LP) wave and a dual circularly polarized (CP) wave. The frequency responses of the gain and axial ratio are calculated.

Circular polarized aperture coupled patch antennas for an RFID system in the 2.4 GHz ISM band

Abstract: The design of aperture coupled patch (ACP) antennas for an RFID system in the 2.4 GHz ISM using circular polarization modulation is presented. Due to the requirements of the modulation scheme the ACP antennas are circularly polarized with switchable polarization sense. Four ACP antennas are compared according to their impedance and gain bandwidth, axial ratio, and crosspolarization isolation. Among the presented antennas a novel compact ACP antenna is shown that allows replacement of the conventional quadrature hybrid polarizer by /spl lambda//4 quarter transmission lines.

Dipole array scan performance over a wide-band

Abstract: A large square array of thin dipoles has a well-behaved scan resistance over a wide bandwidth. Such an array requires reactance matching with frequency, but not with scan angles. The scan element pattern (SEP) shows only small changes over a 5:1 bandwidth, However, a dipole/screen array is suitable for wide-band scan only in the H-plane.

Antenna field tester

Abstract: An apparatus and method for testing of rotating surface based antennas arrays (regardless of their shape), with the capability of fully diagnosing and locating a failure on the face of the antenna by coherently sampling and storing the radiation in the near field and imaging the fully array complex excitation from the stored data. The rotation of the antenna is used in order to collect data for the full azimuth span required for high resolution imaging of excitation in the horizontal domain. Excitation in the vertical domain can be preformed in two ways depending on the type of antenna used. For electronically scanning antennas in elevation (phased array antennas), the phase shifter in the desired row is toggled and the row is isolated by subtracting the complex data from pairs of adjacent samples. The sampling probe is moved vertically while the antenna is rotating horizontally. The vertical movement of the probe provides the aperture necessary to resolve the vertical excitation of the array to a degree of accuracy sufficient for fault detection and isolation.

Planar dual band microstrip or slotted waveguide array antenna for all weather applications

Abstract: Antennas useable in all types of weather conditions are disclosed for use in various applications. The antenna is a flat array with either microstrip or slotted waveguide radiating elements. The radiating elements can be either transmitting or receiving elements for the array, or can be two arrays, each dedicated to one half of the transmission link. The array is covered with a radome to prevent water droplets, ice, or snow from forming on the antenna surface, thus allowing beam launching or beam reception at the antenna surface. The antennas can be used in a wide field of applications, including microsatellite communications links. Also disclosed is a microstrip, dual-band phased array antenna having a top dielectric including an antenna array patch directly coupled to a receive feed network and a lower dielectric having a transmit feed that is coupled to the antenna array patch through an intermediate metallization layer having coupling slots.

A perpendicularly-fed patch array for quasi-optical power combining

Abstract: A quasi-optical power combining amplifier array employing a perpendicular feed structure is introduced. The amplifier array uses aperture-coupled microstrip patch antennas with a unique feed structure for both the input and output antennas. This feed places the devices and antennas on separate planes, allowing for a smaller unit cell size, a simplified layout, and a minimum interaction between the devices and fields. A 5/spl times/5 amplifier array was designed and fabricated at X-band. Results for the gain and power compression are given.

A Broadband Quasi-Yagi Antenna Array

Abstract: A broadband quasi-Yagi X-Band antenna array with a fanbeam-pattern is presented. The bandwidth of the array (VSWR < 2.0) is found to be 50% and a measured gain of 10-12 dB is measured in the operating range. An array with a 12° beam tilt is also presented. The endfire array demonstrates a front-to-back ratio better than 20 dB and cross-polarization better than ?15 dB in the operating band. The fanbeam pattern is useful for mobile communications applications. Active 2-D arrays based on this concept should prove useful for radar, communications and quasi-optical power combining applications.

Analysis of field strength levels near base station antennas

Abstract: A new hybrid algorithm to evaluate the field strength levels around base stations antennas of cellular mobile radio systems is presented in the paper. The method allow a correct evaluation of near and far radiated field by means of the combination of different propagation models. The field intensity level is compared with measurements for some typical urban base stations and an analysis of the impact of the presence of buildings or other objects is also performed. We identify the areas around the antennas where the field strength level exceeds the exposure limits specified in the IRPA Guidelines of 1988 and CENELEC ENV 50166-2 report of 1995. As a result of this analysis we propose a preliminary classification of different installations based on few fundamental parameters related to the antenna characteristics and to the environment topology.

A 3-D extrapolation model for base station antennas' radiation patterns

Abstract: This paper presents a new and simple method for the estimation of 3-D radiation patterns, based on the horizontal and vertical ones, that leads to lower errors compared to some common methods. In order to evaluate the reliability of this method, it has been tested for various theoretical cases, by considering dipoles, individually or in arrays. For the case of the half-wavelength dipole, a maximum error of 12.0 dB (for directions of very low radiation) and an average one of 1.6 dB were obtained; for an uniform array of two dipoles radiating in a half plane (which leads to a similar GSM panel antennas' radiation pattern) the average error was 1.8 dB (in the whole sphere). Measurements were also conducted in a real GSM network, and different approximations for the base station radiation pattern were compared. The model presented here leads to the lower error, its average absolute value being 4.0 dB.

Conformal aperture coupled microstrip phased array on a cylindrical surface

Abstract: A C-band conformal aperture coupled microstrip patch phased array was modelled and fabricated. The measured results show the capability of the array to form a directive sector beam as well as an omnidirectional pattern within the measured bandwidth of 19%. As the gain variation is negligible while scanning the direction of the array, it is recommended for 360/spl deg/ cover in communication systems.

Effect of element spacing and curvature on the radiation patterns of patch antenna arrays mounted on cylindrical multilayer structures

Abstract: We have developed a computer program which calculates radiation patterns of an array of N/spl times/N patch antennas located above or inside a multilayer circular cylindrical structure by using the spectral domain approach. In the present paper, we use the program to study the effects of the curvature of the structure on the radiation pattern. The results show that the radiation pattern in the azimuthal direction is strongly dependent on the cylinder radius but much less so in the elevation direction. The results also show that the array exhibits high sidelobes which can be reduced by making the element spacing smaller than is necessary in the planar array.

Compound dipole with H-plane parasitic posts for phased array wide-angle wide-band scanning

Abstract: This paper presents the structure of a compound dipole with H-plane parasitic posts in an array and describes its radiation characteristics. The simulation result indicates that this dipole is not only useful for eliminating scanning blindness to achieve a wide angle-scanning, but also for improving the reflection coefficient for wide-band matching. By use of the dipole in a 7/spl times/7 array plane and an 8/spl times/10 active phased array, very good wide-band consistencies are shown experimentally.

Experimental adaptive cylindrical array

Abstract: An adaptive antenna places nulls in its antenna pattern in the direction of the interfering sources. Adaptive antennas are a subset of smart antennas, and have received considerable interest in the recent wireless revolution. This paper presents a successful application of a genetic algorithm with an experimental antenna for placing a null in the direction of an interference source. The experiment took place at the Air Force Research Laboratory (AFRL)/Sensors Directorate, Hanscom AFB, MA. Results show that a null can be placed down to the noise floor of the measurement system within 20 to 50 power measurements. Thus, the approach to adaptive nulling is a viable means of quickly placing a null in the sidelobes of a phased array antenna.

Challenges in PCS antenna design

Abstract: We review some of the challenges facing the designers of personal communication services (PCS) antennas and provide some examples that have been proposed to meet these challenges. Approaches to size reduction include the use of high dielectric constant materials, employing dielectric resonator, inverted-F or meander patch antennas.