Fresnel zone

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

Millimetre-wave polarization-dependant monopulse printed Fresnel reflector

Abstract: This article describes the principle of combining circular or annular patches with C-patches on a Fresnel reflector that introduces radiation pattern diversity according to the polarization. Patches were designed to perform a 180° phase difference of the reflection phase between two orthogonal polarizations for a monopulse antenna purpose. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 25–28, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24822

Method for determining wireless transmission characteristics

Abstract: There is provided a method of simulating one or more links in a network based on a simulated link to determine wireless transmission characteristics; the method comprises: placing a first point corresponding to an access point and a second point corresponding to a radio device on a map of geographic locations; simulating transmission characteristics of a link between the first and second points based on a free space loss (FSL), a received signal level (RSL), a Fresnel zone (Fresnel zone) and a rainfall rate; and displaying an indicator of the quality of the transmission characteristics on oneor more lines connecting the plurality of points.

A microwave absorption spectrometer based on three-ray propagation

Abstract: The classical Fresnel zone criterion is used to examine microwave propagation through an open ended cylindrical metallic tube. It is shown that there exists a near free-space propagation region between the transmit antenna and the receive antenna. This principle is used to develop a microwave absorption spectrometer. Experimental results are presented to validate the concept.

15 – zone plates

Abstract: Publisher Summary The chapter discusses zone plates. Imaging in a projection or a probe (scanning) mode requires a focusing element. A lens is used for this purpose in visible and near-ultraviolet (W) light. In this case, the curvature of the surface and the effective diameter of the lens will be of the order of several microns. Because of the fact that only a few Fresnel zones are utilized, the resolution is of the order of the lens diameter, which makes this lens hardly more useful than a pinhole. To reduce the thickness of the lens (and improve transmission), the material can be removed while maintaining proper optical path differences, thus creating a Fresnel lens, such as is used in lighthouses, searchlights, and overhead projectors. In a final state, the thickness variation within every Fresnel zone of the lens provides a phase shift from 0 to 360o. The similarity of a zone plate and a lens is not limited by the lens formula. The radial resolution of a zone plate is very close to that of a lens. The intensity of light focused by a zone plate is calculated by integrating the amplitude of a diffracted wave over a pair of adjacent zones and summation of the contributions of all zone pairs. The resulting intensity normalized to the incident flux is the efficiency of the zone plate.

Inverse Filtering to Minimize the Effect of Mechanical Aberration in Focusing Piezoelectric Transducers

Abstract: The resolution of acoustic images from a “positively scanning transmitter” system is limited by the size of the focal spot of the acoustic beam. Frequently a spatial focusing electrode pattern, such as a Fresnel zone plate, is used to excite the piezoelectric transducer of such a system. However, the transformation of that electrode pattern to the acoustic pattern actually generated is not exact. This effect, called mechanical aberration, is a result of wave generation and propagation in the piezoelectric plate and can be represented by a spatial transfer function. The aberration enlarges the focal spot and decreases the resolving power of the instrument.