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早在1933年,Schelleng,Burrows和Ferrell等人就把光学中的不透明半平面绕射理论移植到无线电电波传播中来,并且指出:围绕着不透明屏障边缘绕射的,不只是发射天线的直射波,而且可能还有屏障至接收天线,屏障至发射天线之间地面的反射波.(1)按收点尺的场强,由这四种电波干涉合成,只要相位适当,接收场可以得到加强.如图(1).之后,人们一直认为这种“四射线”绕射理论只有学术上的意义,而不能反映无线电波传播中的实际现象.随着超短波通讯技术的发展,直到1948年人们开始对这种传播现象进行了探索性试验,结果发现:当超短波通过山岳障碍绕射传播,比没有山岳存在时存在着场强
As early as 1933, Schelleng, Burrows and Ferrell et al. Transplanted the opaque half-plane diffraction theory in optics into radiowave propagation and pointed out that not only the direct waves that radiate around the opaque barrier edges (1) According to the strength of the receiving ruler, the interference of these four kinds of radio waves can be synthesized. As long as the phase is appropriate, the receiving field can be strengthened. (1) .Then people always think that this “four-ray” diffraction theory has only academic significance, and can not reflect the actual phenomenon of radio wave propagation.With the development of ultra-short wave communication technology, until 1948 people began An exploratory test of the phenomenon of propagation shows that when there is a field strength when the ultrashort wave is diffracted by the mountain obstacle,