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一、前言绝大多数天线都是与频率有关的装置。当工作频率发生变化时,天线的输入阻抗和功率方向图都要发生变化,这是因为以波长数表示的天线实际尺寸不是常数。设计与频率无关的宽频段天线是多年来许多研究工作的课题。Rumsey是首批指出设计与频率无关的天线的基本必要条件的人之一。他认为:如果能完全用角度来表示天线的尺寸,那末天线的性能会与频率无关。Du-Hamel和Isbell把角度概念与周期性结合在一起加以考虑,结果制成了一系列
I. INTRODUCTION Most antennas are frequency-dependent devices. When the operating frequency changes, the antenna’s input impedance and power pattern should be changed, because the actual number of wavelengths in the antenna is not a constant size. Designing frequency-independent broadband antennas has been the subject of much research work over the years. Rumsey was among the first to point out the basic requirements for designing antennas that are frequency independent. He believes that if the angle can be completely represented by the size of the antenna, then the performance of the antenna has nothing to do with the frequency. Du-Hamel and Isbell take the concept of angle into consideration periodically, resulting in a series of