Showing papers on "Conformal antenna published in 1990"

Tape type microstrip patch antenna

Abstract: Single or multiple players of electrically insulating tape have adhesive applied to one surface for the dielectric of the patch antenna. Electrically conductive foil tape with adhesive applied to one surface is used to create the radiating element and the ground plane. The antenna structure can then be mounted to the desired surface by means of structural tape adhesives. The resultant sandwich structure forms a highly flexible, low profile, low cost, rugged conformal antenna for radiating radio frequency energy. Modification and control of the electrical and performance characteristics of the antenna can be accomplished by non-uniform thickness of the dielectric, using insulating tape sections which differ in dielectric constant, incorporating PIN diodes with optical of electrical control, etc.

Superconducting antennas

Abstract: It is noted that the advent of high-T/sub c/ superconducting materials has prompted a reexamination of the opportunities for improving antenna performance. Areas where superconductors have potential are considered, including superdirective arrays; large millimeter wavelength arrays; electrically small antennas; matching of electrically small antennas, including large transmitting antennas, and of superdirective arrays; switched line or single line phasers for electronic scanning of arrays; and traveling wave arrays where the transmission line phase velocity controls the beam angle. It is concluded that arrays above 5 GHz will benefit from low conduction, and probably also from low dielectric losses. Matching of electrically short antennas, both small (high-frequency) and large (low-frequency), and of arrays of moderate superdirectivity, will allow significant efficiency improvement. >

Experimental results with mobile antennas having cross-polarization components in urban and rural areas

Abstract: The receiving performance of mobile antenna systems that have vertical and horizontal elements at the 920-MHz band has been investigated by measurements in both rural and urban areas in Japan. Three types of inverted-F antennas for a car and three types of antenna elements, a monopole, a bent-slot and an inverted-F antenna, for portable equipment were used in the experiments. The average received power and its probability density function are obtained as the parameter to evaluate the performance of antenna systems. The performances of the bent-slot antenna system for portable equipment and the inverted-F antenna system mounted on a car are compared with those of the monopole or dipole antenna systems used as reference antennas. A notable increase in the average received power has been observed in operation in an urban area where the field distributes randomly and consists of cross-polarized components. >

A phased array tracking antenna for vehicles

Abstract: An antenna system including antenna elements and a satellite tracking method is considered a key technology in implementing land mobile satellite communications In the early stage of land mobile satellite communications, a mechanical tracking antenna system is considered the best candidate for vehicles, however, a phased array antenna will replace it in the near future, because it has many attractive advantages such as a low and compact profile, high speed tracking, and potential low cost Communications Research Laboratory is now developing a new phased array antenna system for land vehicles based on research experiences of the airborne phased array antenna, which was developed and evaluated in satellite communication experiments using the ETS-V satellite The basic characteristics of the phased array antenna for land vehicles are described

Multiple antenna system with output signal combination

Abstract: The antenna combination has at least two individual antennas which form part of at least one resonant circuit which appears on an electrically conductive surface. The output signals of the individual antennas are combined, for example, added. The antennas are preferably located at the edges of the electrically conductive structure. The antenna combination of the invention is particularly suitable for transmitting and receiving in vehicles because antennas which have transmitting and receiving properties equivalent or superior to those of rod and disc antennas can be built into the vehicle. The antenna combination can be used advantageously in a diversity process.

Applications of photonic technology to phased array antennas

Abstract: The photonic features that can benefit the system performance of airborne and ground-based array antennas are enumerated. It is pointed out that the wide instantaneous bandwidth is probably the most attractive characteristic, holding great promise for performance improvement of future radar, communication, and electronic warfare systems. The impact of photonic technology on the array architecture design is discussed. The development of a dual-band transmit array (X-band and L-band) controlled by a time shift beamforming network is considered. >

Metal-strip-loaded rectangular dielectric rod leaky-wave antennas: experimental verification of a new simple theory

Abstract: An earlier simple and accurate theory for the class of metal-strip-loaded dielectric antennas is extended to the case of narrower antennas, where the width to grating period is significantly less than 4 to 1. This extension is based on the effective dielectric constant method, and is therefore very simple. Careful measured data for two representative structures, a wide antenna and a narrow one, are presented, and it is shown that the theories for both cases are sufficiently accurate for engineering design. Comparisons between measurement and theory demonstrate the validity of the theories for both the wide and narrow cases, verifying the earlier theory for wider antennas and the current extension to narrower widths. The theory and its simple extension are shown to be sufficiently accurate for the design of millimeter-wave antennas with prescribed characteristics. >

Lens-Fed Microwave and Millimetre-Wave Receivers with Integral Antennas

Abstract: A family of microwave receivers is described with antenna and semiconductor components integrated on a common substrate, in a space small enough for packing into arrays. The antenna pattern is suitable for feeding via a dielectric lens, and a balanced mixer and I.F. amplifier are integrated on the antennas. Such receivers have been built to operate around 10 and 35 GHz, and show conversions loss similar to more conventional designs.

Vehicle terminal antennas for mobile satellite applications

Abstract: A review of three classes of antennas for data and voice terminals is presented. The first one is a conically shaped beam low-gain antenna for data terminals. Drooping dipoles, quadrifilar helices, and microstrip antennas are described. These antennas can be simple and inexpensive . The second type of mobile terminal antennas are medium gain: microstrip mechanically steered arrays, microstrip electronically steered arrays, and adaptive arrays with a simple beam-steering system. The third type is a high-gain fixed terminal antenna. The noise temperature and G/T values of some antennas are discussed. The results of the vehicle terminal antennas program at AK Electromagnetique in support of developing North American mobile and fixed satellite services are summarized. >

Performance of a Spherical Array Antenna Fabricated by Vacuum Forming Technique

Abstract: In this paper, a spherical array antenna applicable to mobile satellite communications is discussed. The beam scanning characteristics of the directive gain of spherical and planar arrays are examined by computer simulation, and it is shown that the gain reduction of a spherical array is suppressed about 2 dB at a scan angle of 60° compared with that of a planar array. Mechanical and electrical performance of a vacuum formed hemispherical array is introduced. Experiment results show the feasibility of easily fabricated conformal arrays with good electrical performance.

Cylindrical Phased Array Antenna for SSR-Mode S System

Abstract: A cylindrical conformal phased array antenna which is a candidate of SSR(Secondary Surveillance Radar) antenna for next generation is experimentaly constructed and tested. This antenna is consisted of broadband microstrip patch antennas. Band broadening is achieved by honeycomb structure[1] [2] and attains about 6% bandwidth. In order to obtain a good elevation pattern, mutual coupling effect is considered in design and the fine elevation pattern is obtained.

New analysis of beamwaveguide antennas considering the presence of the metallic tube and its experimental verification

Abstract: Large beamwaveguide (BWG) type ground station antennas are usually designed using analysis that ignores the presence of the metallic tube enclosing the beamwaveguide mirrors. A novel and fundamentally more correct BWG analysis which considers the presence of the metal tube is presented. Numerical results on a two-mirror system using the analysis are compared with experimental results. A BWG was used to test the effects of the enclosing metallic tubes on the performance of BWG antennas. Measurements of the two-mirror system with and without the metal tube are found to validate the analysis. >

Application of time-domain finite-volume method to antenna and array problems

Abstract: A preliminary study regarding the potential of a time-domain finite-volume method to solve radiation problems has been carried out. The results of this preliminary study are very encouraging and reveal a great potential in dealing with various kinds of radiating structures. This potential in the area of printed antennas is particularly important because printed antennas often comprise multilayers of dielectric materials with nonplanar profile. Another area of application of the proposed method is computation of antenna transients and radiation due to nonsinusoidal excitations. Some sample results are presented, namely radiation contours and radiation patterns for an open-ended parallel-plate waveguide, a two-dimensional horn, and a binomial array of parallel-plate waveguides. >

Optical beam-former for microwave phased array antennas

Abstract: Presents a new beam forming technique for use in optically controlled phased array antennas The system uses two optical fibre networks to produce a beam having independently specified frequency and aperture phase slope The theory of the system is presented together with a description of the experimental implementation and results for a system operating at L-band

Antennas for direct to home reception of DBS television

Abstract: Outdoor units were required for domestic DBS TVRO stations. Satellites had been ordered to provide 59 dBW EIRP or more, as had receivers incorporating custom DMAC integrated circuits and eurocypher modules. It was established that an antenna aperture width of about one foot would be required and that the antenna could be either a parabolic dish or a flat plate array. Research confirmed that both flat plate arrays and offset-feed parabolic reflector antennas are acceptable to the market. Two Squarial arrays and two reflectors were made available by approved manufacturers in time for launch of BSB programmes. The antennas are designed to facilitate installation by professionals and by the DIY enthusiast. An installation display facility was incorporated in the receiver to monitor the DMAC bit error rate.

Some HP system design considerations for aircraft

Abstract: The author discusses the fundamental limitations of electrically small radiators and their significance to electrically small antennas. Some of the parameters are derived. Systems incorporating electrically small radiators are constrained by fundamental limitations to be either inefficient or narrowband. These conditions are apparent in the case of aircraft HF (2-30 MHz) antenna systems, particularly for small aircraft at the low end of the band. The author discusses the HF antenna problems for aircraft, in particular the need to distinguish between the airframe and the antenna. The types of antenna used, loops and notches, are discussed. Examples of measurements for a BAC 1-11 airliner and a helicopter are given.

Predicting the Performance of Airborne Antennas in the Microwave Regime

Abstract: : This study investigated the application of a high-frequency model (Uniform Geometrical Theory of Diffraction) of electromagnetic sources mounted on a curved surface of a complex structure. In particular, the purpose of the study was to determine if the model could be used to predict the radiation patterns of cavity-backed spiral antennas mounted on aircraft fuselages so that the optimum locations for the antennas could be chosen during the aircraft design phase. A review of literature revealed a good deal of work in modeling communications, navigation, identification antennas (blade monopoles and aperture slots) mounted on a wide variety of aircraft fuselages and successful validation against quarter-scale model measurements. This study developed a monopole-array model of a spiral antenna's radiation at vertical polarization and an ellipsoid-plate model of the FB-111A. Using the antenna and aircraft models, the existing Uniform Geometrical Theory of Diffraction model generated radiation patterns which agreed favorably with full-scale measured data. The study includes plots of predicted and measured radiation patterns from 2.5 to 15 Gigahertz. Theses (rrh)

Development of millimeterwave antennas in slotline technique for integrated communication systems

Abstract: Slotline millimeter-wave antenna designs using the theory of unilateral finlines and slotlines are described. Several antenna shapes, such as Vivaldi radiators and equivalent horns, were developed at 32 GHz. These types of antennas make possible a direct integration of certain communication systems with their antennas. Particular attention is given to the development of monolithic integrated transceivers on GaAs which will be connected to an antenna on an RT-Duroid substrate by hybrid techniques. The feasibility of the proposed technique is demonstrated. >

A high gain antenna system for airborne satellite communication applications

Abstract: A high gain antenna for commercial aviation satellites communication is discussed. Electromagnetic and practical design considerations as well as candidate systems implementation are presented. An evaluation of these implementation schemes is given, resulting in the selection of a simple top mounted aerodynamic phased array antenna with a remotely located beam steering unit. This concept has been developed into a popular product known as the Canadian Marconi Company CMA-2100. A description of the technical details is followed by a summary of results from the first production antennas.

Modern analysis methods for medium wave antenna design

Abstract: Antenna arrays, sectionalized antennas, and antennas which are electrically in the vicinity of 1/2 wavelength in length, can be difficult to design. These types of antennas are good candidates for moment method analysis. A few examples are included to demonstrate the usefulness of moment method techniques in practical situations. Moment method techniques are a powerful and valuable tool for the antenna designer. Personal computers are widely available, as are well documented and tested programs such as NEC and MININEC. The existence of this technology has created the opportunity for more complete design capabilities, as well as easier and more certain adjustment processes for the antenna engineer. These techniques must be used with care, as is the case with all problem-solving that involves complex computer programs, but they have become a major modernizing influence on medium wave antenna engineering. >

SATCOM antenna siting study on a P-3C using the NEC-BSC V3.1

Abstract: The location of a UHF SATCOM antenna on a P-3C aircraft is studied using the NEC-Basic Scattering Code V3.1 (NEC-BSC3). The NEC-BSC3 is a computer code based on the uniform theory of diffraction. The code is first validated for this application using scale model measurements. In general, the comparisons are good except in 10 degree regions near the nose and tail of the aircraft. Patterns for various antenna locations are analyzed to achieve a prescripted performance.

Radar simulator device

Abstract: PURPOSE:To simplify the constitution and to reduce limits due to a pitch interval by combining an elliptic surface mirror, a plane antenna, a phased-array antenna, and a conformal array antenna CONSTITUTION:The plane antenna 14 and a radar antenna 3 to be measured are placed at the focuses 15 and 15 of the elliptic surface mirror A dummy signal generating circuit radiates information on a distance, a speed, etc, from the plane antenna 14 in a direction indicated by a computer 12 A signal radiated from one focus 15 is reflected by the elliptic surface mirror 13 and received by the radar antenna 3 to be measured at the other focus 15 The beam direction of the radiated signal changes by the rotation of the plane antenna 14 on the focus 15 and the incidence angle direction changes when viewed from the radar antenna 15 to be measured, so that a target seems to move The plane antenna 14 is driven to change its direction, thereby simulating the movement of the target

A new approach to the design of a broadband active loop antenna 50 kHz-30 MHz

Abstract: The author discusses improvements in the design of active loop receiving antennas. The improvements include segmenting a large diameter single loop into a number of equal smaller loops. This allows the source inductance to be adjusted as required. When this loop array is connected to a common base amplifier a substantial improvement in sensitivity is achieved in the frequency range 3 to 30 MHz. Loop antennas have other attributes. Directivity in the horizontal plane aids rejection of unwanted signals and the absence of a null in the vertical plane makes high angle skywave reception much better than with the vertical monopole. The loop antenna can also be effectively decoupled from local sources of interference which is not possible with monopole antennas and which have the added disadvantage that the feeder forms part of the antenna.

Automated antenna test range for small antennas

Abstract: During the past two years the Antennas/Propagation group at NovAtel Communications Ltd has developed a unique automated Antenna Test Range (ATR). This facility is capable of measuring the entire far field radiation pattern of small antennas and displaying the results in two and three dimensional polar plots. This is accomplished by connecting a battery powered transmitter to the Antenna Under Test (AUT) and rotating it about two orthogonal axes. The emitted radiation is sampled over a spherical surface centered about the AUT. The manner in which the measurements are taken permits the hardware for the ATR to be fairly simple and inexpensive, while the software required to gather and process the data is fairly complex. Using this facility NovAtel is able to research and develop unique antennas for future products such as handheld cellular telephones and Global Positioning Systems. This paper presents a general description of the facility's operation and typical test results.

An equivalent model for practically used dipole-type antenna elements

Abstract: A simple equivalent model is presented which represents antenna elements that make up various types of TV receiving array antennas. The model gives a unified representation of eight different types of antenna elements, such as loaded and unloaded folded types, conventional dipole types, loaded and unloaded parasitic element types, etc. This model can be used to conveniently analyze the radiation characteristics of many array antennas which are made by combining these dipole-type elements into various TV receiving antennas. >

The analysis of reactively loaded microstrip antennas by finite difference time domain modelling

Abstract: In recent years, much interest has been shown in the use of printed circuit antennas in mobile satellite and communications terminals at microwave frequencies. Although such antennas have many advantages in weight and profile size over more conventional reflector/horn configurations, they do, however, suffer from an inherently narrow bandwidth. A way of optimizing the bandwidth of such antennas by an electronic tuning technique using a loaded probe mounted within the antenna structure is examined, and the resulting far-field radiation patterns are shown. Simulation results from a 2D finite difference time domain (FDTD) model for a rectangular microstrip antenna loaded with shorting pins are given and compared to results obtained with an actual antenna. It is hoped that this work will result in a design package for the analysis of microstrip patch antenna elements.

HELIXANT: a normal mode helix antenna prediction program

Abstract: The resonant normal mode helix antenna (NMHA) is being studied for adaptation to command and control systems requiring low-profile, compact antennas. The authors describe HELIXANT, a computer program for modeling this type of antenna and obtaining quantitative predictions of performance. The HELIXANT program listing and its validation are considered. Based upon comparisons with other prediction methods and test results, HELIXANT appears to be useful as an accurate and easy-to-use tool for complete analytical prediction of NMHA behavior for HF, VHF, and UHF frequency ranges. >

Wideband ortho-mode Vivaldi antennas

Abstract: The wideband ortho-mode Vivaldi antenna is composed a set of spatially orthogonal Vivaldi elements suitably fed by an ortho-mode tee. The design considerations and the practical results for two prototypes are given and discussed. >