预测隧道中传播损耗的混合模型

本文运用Fresnel区域理论,得到了计算转折点距离的公式,结合自由空间传播模型和修正的波导模型,提出了一种新的混合模型.各种条件下的实验数据都验证了模型的合理性.结果表明,转折点以前的传播损耗可用自由空间的传播模型预测,而在转折点之后,可通过修正的波导模型预测.

A Hybrid Model for Propagation Loss Prediction in Tunnels

The Fresnel zone theory is employed to determine the boundary to distinguish propagation regions for line-of sight topographies in tunnels. The formula for calculationg the break point distance is obtained. A hybrid propagation model combining the free space propagation model and the modified waveguide propagation model is proposed. The hybrid model and the break point distance formula are validated with our own and other published experimental data in various tunnels and at different frequencies. It is shown that the free space propagation model can be used to predict propagation loss in region prior to the break point , while the modified waveguide propagation model offers excellent prediction of propagation loss after break point.