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一、概述从天线辐射出来的信号,经过不同的路径传播到接收点。在发射天线和接收天线之间通过直接路径传输的信号叫做直达波。从地表面反射之后到达接收天线的信号叫做反射波。直达波和反射波合称为空间波,沿地球表面传播的波叫做表面波。一般把表面波和空间波统称为地波。当发射天线和接收天线都非常接近地面吋,空间波中的直达波和反射波相互抵消,地波完全是表面波。见图4.1。
First, an overview of the radiation from the antenna signal, through a different path to the receiving point. The signal transmitted over the direct path between the transmitting antenna and the receiving antenna is called direct wave. The signal that reaches the receiving antenna after being reflected from the ground surface is called the reflected wave. Direct and reflected waves are collectively referred to as spatial waves and waves propagating along the surface of the Earth are called surface waves. Surface waves and space waves are generally referred to as ground waves. When the transmitting antenna and the receiving antenna are very close to the ground, the direct wave and the reflected wave in the space wave cancel each other out and the ground wave is completely the surface wave. See Figure 4.1.