隧道内微波多径传播特性的仿真

运用射线法和帐篷定律模型对空直矩形隧道微波载波的多径传播特性进行了仿真研究。结果表明，隧道中信号传输的时延扩展和信号的衰减均与载波频率有关。载频越高，时延扩展越小，而衰减越大。这是由于在相同的隧道壁粗糙度下，波长短的信号散射衰减更大，因而具有较少的反射路径。此外，隧道中垂直极化波的时延扩展比水平极化波的要小，原因是隧道壁对不同极化波反射衰减不同。

The Simulation of Multipath Propagation Characteristic of Microwave in a Tunnel

Tent law and ray tracing method were used to simulate the multipath propagation characteristic of microwave in rectangular tunnel. Simulation results showed tha t, with the same roughness of a tunnel, both the delay spread and the signal att enuation varied with the carrier frequency. The higher the frequency, the smalle r the delay spread, but the larger the propagation attenuation. It was due to th e scattering effect. High frequency carrier, with short wavelength, will suffer larger scattering attenuation at each reflecting spot, therefore the number of m ultipath routes decreases. In addition, the delay spread of vertical polarized w ave is smaller than that of parallel polarized wave. It was due to the differenc e of reflecting coefficients of vertical polarized wave and parallel polarized w ave.