Fresnel zone

About: Fresnel zone is a research topic. Over the lifetime, 2337 publications have been published within this topic receiving 37650 citations.

Flat mirror antenna

Abstract: PURPOSE:To improve the manufacturing efficiency of the antenna so as to reduce the manufacturing cost and time by providing a metallic diffraction ring, metallic reflecting plate which is arranged so that the reflecting plate can face the diffraction rig at an interval of about 1/4 wavelength, and pickup antenna section which is arranged near the focusing position of the diffraction ring. CONSTITUTION:A dielectric reinforcing plate which supports and fixes a diffraction ring 1 and reflecting plate 2 is provided between the ring 1 and plate 2. A pickup antenna section 3 for reception is supported at the focusing position of the ring 1 by means of a supporting arm 8. In a Fresnel zone formed in a radio wave propagating path between a transmitting and receiving points, same-phase components are converged to the antenna section 3 provided at the focusing position of the ring 1 after the components are reflected by the ring 1 and, at the same time, opposite-phase components passed through the ring 1 are converged to the antenna section 3 as same-phase components after the components are reflected by the reflecting plate 2 provided at an interval of about 1/4 wavelength from the ring 1 and their phases are matched.

The Effect Of Semiconductor Processing Upon The Focusing Properties Of Fresnel Zone Plates Used As Alignment Targets

Abstract: The use of Fresnel Zone Plates as alignment targets for both x-rayl and optical2 lithography has generated a need for understanding their focusing properties after they have been exposed to semiconductor processing procedures. Semiconductor processing can result in variation of radial dimensions, variation of contrast, and in variation of topography, all of which can impact upon the focusing properties. In this paper we report our measurements and calculations of the axial and radial intensity distribution of monochromatic light on zone plates used for optical alignment purposes. Measurements of the axial and radial intensity distribution were made with a conventional metallurgical microscope with the white-light source replaced with a HeNe laser. Calculations were an approximate solution of the Fresnel-Kirchoff Integral and an exact solution of Maxwell's Equations. 2 For Fresnel Zone Plates exhibiting r2 symmetry where the radii are given by rm = mAfl, m = 1,2,3.....2N, where N= the number of periods and fl = the primary focus, theory indicates that equal intensities be observed at ± fl, A‚± f3, ± f5,.....where f3, f5, are the odd submultiple foci. Even submultiples are zero. The linewidth decreases as the submultiplier increases. For a Fresnel Zone Plate with f1 = 200 microns, N=4 and X = 632.8nm, we observe equal intensities at ± f1 and ± f3 and reduced intensity at ± f5. The linewidth at fl is about a factor of ten larger than at f3. With alteration of the r2 symmetry, even-valued submultiple foci appear first, and with continued variation a total redistribution of the light along the z-axis is observed. Variation of the reflectivity of the zones, variation of the thin-film thicknesses and variation of the optical path difference bewteen zones can result in large intensity variations at the primary focus. The superposition of photoresist with neither conformal nor planarizing topography can result in loss of intensity. However, if the photoresist thickness is properly chosen this loss is not significant. Several processing examples are given.

A software design tool for microwave radio

Abstract: This paper deals with wave propagation calculation and cost optimization software development for microwave radio. The software presents a design tool for line of sight link planning. The main cost factor in a microwave network depends on tower structure and antenna heights. Antenna heights are normally chosen to overcome the first Fresnel zone obstruction. A software tool for the analysis and evaluation of a single microwave relay link has been developed. In addition, cost optimization method for a microwave radio network involving more than two antennas has been developed. This paper includes calculations and analysis of the geographical data in the chosen area in order to determine the effective earth's radius to achieve better optimization. In addition, terrain profile generation and microwave point-to-point link calculation was considered

Wideband printed fresnel reflectarray antennas using dual-printed-dipole elements

Abstract: In this paper, two Fresnel reflectarray antennas, based on two double-layered-dipole periodic elements of different size, are presented and studied. The quarter-wave Fresnel zone principle is applied to the antenna designs. Simulated results show that the Fresnel reflectarray antenna with small unit cells provides better radiation performance.

Land Cover Consideration in Mobile Radio Field Strength Prediction

Abstract: This article treats several aspects of field strength prediction, especially concerning the land cover influence on mobile radio links. A measure for the shadowing influence of buildings and trees in an area with mixed land cover, based on the first fresnel zone ellipsoid, is given as well as an approach to calculate wave propagation in a city with regular building structure and a rectangular street grid. In addition, different definitions of the transmitter's effective antenna height are discussed.