天线的性能-外文文献翻译译文.doc

英文论文翻译 天线性能 目录 TOC \o 1-3 \u PROPERTIES OF ANTENNAS PAGEREF _Toc14429 2 2.1 ANTENNA RADIATION PAGEREF _Toc30083 3 2.2 GAIN PAGEREF _Toc7677 5 2.3 EFFECTIVE AREA PAGEREF _Toc16832 8 2.4 PATH LOSS PAGEREF _Toc2068 8 2.5 RADAR RANGE EQUATION AND CROSS SECTION PAGEREF _Toc17583 10 2.6 WHY USE AN ANTENNA? PAGEREF _Toc13006 12 天线的功能 PAGEREF _Toc17549 12 2.1天线辐射 PAGEREF _Toc25386 13 2.2 天线增益 PAGEREF _Toc4916 15 2.3天线有效面积 PAGEREF _Toc2345 17 2.4路径损耗 PAGEREF _Toc22525 18 2.5雷达距离方程和截面 PAGEREF _Toc20631 20 2.6为什么使用一个天线？ PAGEREF _Toc4604 21 英文原文： PROPERTIES OF ANTENNAS One approach to an antenna book starts with a discussion of how antennas radiate. Beginning with Maxwell’s equations, we derive electromagnetic waves. After that lengthy discussion, which contains a lot of mathematics, we discuss how these waves excite currents on conductors. The second half of the story is that currents radiate and produce electromagnetic waves. You may already have studied that subject, or if you wish to further your background, consult books on electromagnetics.The study of electromagnetics gives insight into the mathematics describing antenna radiation and provides the rigor to prevent mistakes. We skip the discussion of those equations and move directly to practical aspects. It is important to realize that antennas radiate from currents. Design consists of controlling currents to produce the desired radiation distribution, called its pattern .In many situations the problem is how to prevent radiation from currents, such as in circuits. Whenever a current becomes separated in distance from its return current, it radiates. Simply stated, we design to keep the two currents close together, to reduce radiation. Some discussions will ignore the current distribution and instead, consider derived quantities, such as fields in an aperture or magnetic currents in a slot or around the edges of a microstrip patch. You wi