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引言菲涅耳区平板是一种平面装置,可产生电磁波透镜式聚焦和成象。这些效应是由绕射产生的,而不是因折射所致。菲涅耳区平板可将一般的入射平面波转换成聚焦波,将辐射场集中在通常与透镜的焦点有关的狭小区内,如图1所示。相反,当从一适当馈源(如喇叭天线)馈电时,菲涅耳区平板还可用于平行校正传输中的波束。与透镜相比,菲涅耳区平板具有结构简单(平面结构,无曲度)、厚度薄、重量轻、损耗小、成本低等优点。
Introduction The Fresnel zone plate is a planar device that produces electromagnetic wave lens-type focusing and imaging. These effects are caused by diffraction, not by refraction. The Fresnel zone plate converts the normal incident plane wave into a focused wave, concentrating the radiation field in a narrow zone usually associated with the focal point of the lens, as shown in FIG. 1. In contrast, the Fresnel zone slab can also be used to parallel correct beams in transmission when fed from a suitable source, such as a horn antenna. Compared with the lens, the Fresnel zone plate has the advantages of simple structure (planar structure, no curvature), thin thickness, light weight, low loss and low cost.