Topic
Fresnel zone
About: Fresnel zone is a research topic. Over the lifetime, 2337 publications have been published within this topic receiving 37650 citations.
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14 Aug 2001
TL;DR: In this article, the free propagation of a wavefront in an inhomogeneous medium with parabolic refractive index profile and the division of the wavefront into Fresnel zones are studied.
Abstract: The free propagation of a wavefront in an inhomogeneous medium with parabolic refractive index profile and the division of the wavefront into Fresnel zones are studied. We determine the radius and the area of each zone as well as the zone contribution to the total wave at an observation point inside the medium. We find the condition that the optical path must fulfill from each zone to the aforementioned point so that the disturbance due to successive zones will be in phase opposition. Once this condition is settled the concept of zone plate in gradient- index media can be introduced.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
24 Mar 2015
TL;DR: In this paper, two-dimensional hexagonal configurations based on pseudo-random and extended pseudorandom sequences are presented. But the first method involves adding or subtracting elements of traditional hexagonal configuration.
Abstract: New ways of constructing two-dimensional hexagonal configurations based on pseudo-random and extended pseudo-random sequences are presented. The first method involves adding or subtracting elements of traditional hexagonal configuration. Pseudo-rectangular hexagonal configurations with hexagonal cells and their modifications were obtained. All configurations keep their periodicity and ability for mosaic construction allowing using them for creation of multi-pinhole coding collimators for registration of ionizing radiation.
TL;DR: In this paper, a procedure based on the method of stationary phase and that of Fresnel zones is presented for synthesizing a desired impulse response of a time lens, from a pupil function that consists of a series of properly-spaced light pulses of equal heights.
01 Oct 1990
TL;DR: In this paper, propagation experiments and the performance of angle-diversity reception on two different test links were described and outage calculations were performed for 16 QAM and 64 QAM digital radio systems with different parameters using the measured propagation channel responses.
Abstract: The paper describes propagation experiments and the performance of angle-diversity reception on two different test links. One of the test links exhibited a good path clearance with a pronounced height difference between transmitter and receiver terminals, whereas the second link ran parallel to the earth's surface with smaller path clearance given by the radius of the first Fresnel zone. The results for both test links showed that the dispersive nature of the fading is caused mainly by ground reflections or ray bending at ground-based layers. Outage calculations were performed for 16 QAM and 64 QAM digital radio systems with different parameters using the measured propagation channel responses. The results show that propagation impairments can be reduced strongly by angle-diversity reception as compared with single reception for both links. With additional adaptive equalization, outage can be avoided on both links if the flat-fade margin is large enough.