Showing papers on "Fresnel zone antenna published in 1992"

Millimeter-wave and terahertz integrated circuit antennas

Abstract: A comprehensive review of integrated circuit antennas suitable for millimeter and terahertz applications is presented. A great deal of research was done on integrated circuit antennas in the last decade, and many of the problems associated with electrically thick dielectric substrates, such as substrate modes and poor radiation patterns, have been understood and solved. Several antennas, such as the integrated horn antenna, the dielectric-filled parabola, the Fresnel plate antenna, the dual-slot antenna, and the log-periodic and spiral antennas on extended hemispherical lenses, which have resulted in excellent performance at millimeter-wave frequencies, are covered in detail. A review of the efficiency definitions used with planar antennas is included. >

Fresnel volume ray tracing

Abstract: The concept of “Fresnel volume ray tracing” consists of standard ray tracing, supplemented by a computation of parameters defining the first Fresnel zones at each point of the ray. The Fresnel volume represents a 3-D spatial equivalent of the Fresnel zone that can also be called a physical ray. The shape of the Fresnel volume depends on the position of the source and the receiver, the structure between them, and the type of body wave under consideration. In addition, the shape also depends on frequency: it is narrow for a high frequency and thick for a low frequency. An efficient algorithm for Fresnel volume ray tracing, based on the paraxial ray method, is proposed. The evaluation of the parameters defining the first Fresnel zone merely consists of a simple algebraic manipulation of the elements of the ray propagator matrix. The proposed algorithm may be applied to any high‐frequency seismic body wave propagating in a laterally varying 2-D or 3-D layered structure (P, S, converted, multiply reflected, et...

Use of fresnel zone plates for material processing

Abstract: The apparatus for machining and material processing includes an excimer laser and a Fresnel zone plate array (FZP) positioned parallel to the workpiece, with the distance between the FZP and the workpiece being the focal length of the FZP. For each hole to be formed on the workpiece a corresponding Fresnel zone is patterned onto the FZP. Each Fresnel zone may be patterned directly centered over the desired hole location or in high density patterns it may be located off-center from the hole with deflection being accomplished by the formation of finer circular arcs on the side of the Fresnel zone opposite the desired direction of deflection. A beam scanner is included to provide a more uniform illumination of the FZP by the laser beam. The scanning eliminates non-uniformity of intensity. The alignment mechanism uses a helium-neon laser, the beam from which is projected onto a surface relief grating on the workpiece. The reflected light from the surface relief grating is filtered to create interference fringes which, when aligned, provide maximum light intensity projected through a transmission grating on the Fresnel zone plate.

Vectorial far‐field analysis of the fresnel‐zone plate antenna: A comparison with the parabolic reflector antenna

Abstract: An analysis of the radiation properties of the Fresnel-zone plate antenna (FZPA) and the parabolic reflector antenna (PRA) is presented using the Kirchhoff diffraction theory. Expressions are derived for the vectorial far-field radiation patterns of both antennas. Some computed co- and cross-polar patterns are shown. The most important differences between the radiation properties of the FZPA and PRA are revealed and discussed. The results of the analysis give good insight into future applications of the FZPA.

Zone plate lens antennas for millimeter and submillimeter wavelengths

Abstract: Zone plate lenses are a type of focusing element which function essentially as differential phase shifters, having a relatively few, coarsely quantized phase delays across the incident beam of radiation. The major advantages are ease of fabrication and much reduced thickness, compared to conventional refractive focusing elements. These considerations are both of particular importance for the submillimeter range, in which manufacturing tolerances for curved optical elements can pose significant problems, and where the absorption of readily available dielectric materials is quite large. In this presentation we briefly review the theory of zone plate lens operations, present a relatively simple method for calculating the aperture efficiency of zone plate lenses used as antennas, and show some theoretical and measured results in the 100 GHz range.

Single shaped reflector antennas for broadcasting satellites

Abstract: For future direct broadcasting satellites in Japan, precisely contoured beam antennas will be required for onboard antennas. Single shaped-reflector antennas are suitable for that purpose, since they do not need complex feed networks. However, in a previous study, discontinuities in the reflector surface were observed. The problem of the discontinuity was circumvented in this work and the shaped reflectors were successfully designed to produce contoured beams for covering the Japanese islands for the downlink and feederlink antennas. The downlink antenna was fabricated, and the radiation pattern was verified by measurement. The radiation pattern meets the radio regulations imposed on the onboard antenna, such as sidelobe and cross-polarization characteristics. >

A high-efficiency quarter-wave zone plate reflector

Abstract: A multilayered quarter-wave zone plate reflector antenna operating in the microwave range is presented. The theory for designing the reflector and experimental results are given. An efficiency of 55% was obtained with a prototype reflector antenna. >

Unified and generalized Fresnel numbers

Abstract: The concept of Fresnel number is discussed and expressions are derived for misaligned optical systems. For the case of perfectly aligned optical elements, the usual number,N, based on a Fresnel zone concept is found to be given byN = (a 2/λ)(D 1/B 1 +A 2/B 2), whereB 1,D 1 andB 2,A 2 are the transfer matrix elements of the optical systems before and after a circular aperture of radiusa respectively. A modified definition of the Fresnel number is proposed for Gaussian beam propagation. This parameterN′ G, is related to the complex beam parameter and may be represented by the angleθ = tan−1 N′ G, found in the familiar Collins chart and its dual representation. A general relation for the transformation of this Fresnel number is found. The expressions for Gaussian beam transformation are thus simplified, since the waist-waist transform is given byN′ G1 =N′ G2 = 0. Finally, these two kinds of Fresnel numbers are written as tensors when applied to cases involving elliptical apertures, astigmatic beams and nonsymmetrical systems.

A uniformly valid loaded antenna theory

Abstract: A quasi-static layered approximation is used to simplify the layered solution for insulated antennas to the solution of a generalized impedance boundary value problem, whose solution is expressed in terms of an integral. This integral applies to insulated antennas imbedded in a dense medium, insulated antennas imbedded in air (dielectric-coated antennas), and impedance-loaded antennas, all referred to as loaded antennas. The branch cut contribution for large distances is given by the Sommerfeld space wave formula. The physical transition of loaded antennas to bare antennas is investigated through the asymptotic evaluation of this integral. Simple uniform formulas for loaded antenna current are derived and generalized to cover the same range of validity as the integral. The direct calculation of the input admittance is consistent with the derived uniform formula for antenna current. For insulated antennas in a dense medium, the complete transmission line theory describes the antenna current through the transition to bare antennas. >

On the sidelobe performance of Fresnel zone plate antennas

Abstract: The Kirchhoff scalar diffraction integral and the image method are used to investigate the close-in sidelobe performance of the simple and phase reversal circular zone plate antennas. It is found that, with fixed aperture dimension, the sidelobe level of a zone plate antenna depends mainly on N, the number of full wave zones composing the plate. When the aperture field taper is kept constant, the sidelobe level of the zone plate decreases significantly when N increases. This means that, with a given zone plate diameter, a small F/D is favorable for obtaining low close-in sidelobes. For a simple zone plate antenna, adequately lowering the edge illumination intensity does reduce the sidelobe level of a centrally opaque version, but it may raise the sidelobes of a centrally transparent one. For the phase reversal zone plate antenna, it is observed that versions with a central disk and a central aperture yield very similar radiation patterns with sidelobes lower than those of the corresponding simple zone plates. Adequately decreasing the edge illumination level produces lower close-in sidelobes. >

Current status of integrated submillimeter-wave antennas

Abstract: The author presents a summary of the development status for recent high-efficiency integrated antennas that are suitable for low-noise submillimeter-wave receivers. The use of these antennas in planar receivers will result in very-low-noise receivers for frequencies above 100 GHz. The antennas presented here are the quasi-monolithic integrated horn antennas, the substrate-backed spiral and log-periodic antennas, the endfire slot-line antennas on thin membranes, the double-dipole integrated reflector antenna, and the dielectric-filled parabola. >

System for locating fresnel reflections along an optical fiber

Abstract: A system for locating Fresnel reflections along an optical fiber, including an emission circuit for emitting optical pulses which are coupled into the input face of the fiber; a reception and transformation circuit (20) for receiving signals reflected by the fiber and transforming them into electrical signals; a selection circuit (20) for taking the electrical signals and selecting therefrom only those electrical signals which correspond to Fresnel reflections; a comparison circuit (23, 25, 26) coupled to the selection circuit (20) and receiving a comparison reference signal expressing the rank of an arbitrarily-chosen one of the Fresnel reflections; and an evaluation circuit (13, 21, 22, 24, 26) coupled to the comparison circuit (23,25,26) and to the selection circuit (20) so as to locate the point along the fiber that gave rise to the arbitrarily-chosen Fresnel reflection

Submillimeter-wave endfire slotline antennas

Abstract: Endfire slotline antennas have been integrated on a 1.75 mu m-thick dielectric substrate. The thin substrate allows the upper frequency limit of the slotline antennas to be pushed beyond 1 THz. Antennas have been fabricated and tested at 350 and 802 GHz. The patterns exhibit high directivity (15+or-1 dB) and wide bandwidth. In the future, these antennas will be combined with SIS junctions for low-noise astronomical receivers. >

Tolerances on millimetre wave reflector antennas

Abstract: The effects of tolerances in the alignment and manufacture of millimetre wave reflector antennas are described. A formula is given for the relationship between peak gain loss and aperture phase error along with formulae for calculating the phase error from each antenna component. The application of these formulae to approximate the gain error is discussed.

Lessons for pulsed-array radar from quantum light detection

Abstract: Antenna arrays are potentially useful for both the transmission and the reception of trains of electromagnetic pulses. In this paper, we formulate an aiming problem pertaining to an RKA- driven launcher of microwave pulses, and draw on a study of quantum measurements to develop an approach to aiming. Appendix A reviews the behavior of microwave radiation focused at a target in the Fresnel zone. Appendix B derives the antenna current for optimal angular sensitivity of a monopulse radar for a target in the Fresnel zone, very close to the axis.

Performance of a small reflector with a splashplate feed

Abstract: Reflector antennas with aperture diameters of less than ten wavelengths are difficult to design with good sidelobe performance because of blockage problems. A small prime focus reflector for 8.4 GHz has been designed using mode-matching techniques. The design was aimed at providing sidelobes of less than -20 dB without degrading the gain excessively. In order to minimise blockage problems, a splashplate feed was chosen. The diameter of the integrated subreflector must be small and has to be optimised in order to offset blockage losses against diffraction and spillover losses. The feed dimensions must also be optimised to reduce blockage losses. The measured results agree well with predictions. The target of less than -20 dB sidelobes was achieved with an aperture efficiency of 60% and the authors conclude that mode-matching is a useful approach to the design of such small antennas. >

Electron-beam lithography of optical elements for x-ray range (Poster Paper)

Abstract: Experimental investigations and special software for the e-beam exposure system gives the possibility of decreasing the influence of proximity effects and field distortion. The results of creating a focusing element for the soft x-ray range are described: amplitude and phase- contrast Fresnel zone plates as well as reflected Bragg-Fresnel lenses on the base of multilayer x-ray mirrors.

Advanced Design Techniques for the Very Large Compact Range (VLCR) Reflector System

Abstract: The compact range has become a popular measurement tool in the evaluation of microwave antennas in recent years. Larger aperture reflectors operating over the entire microwave and millimeter wave spectrum are now required, Olver (1). In this paper, the state-of-the-art design of a Very Large Compact Range (VLCR) reflector with dimensions of 36 meters × 32 meters is described. This VLCR reflector is predicted to achieve unique levels of performance in the large required quiet zone region of the design.