一、前言超地平射频信号的传播可以是障碍绕射或对流层散射。在绕射传播的情况下,大气折射指数的变化引起明显的天线波束向上或向下弯曲,结果使接收信号减弱和衰落掉。对于对流层散射传播,大气折射指数的变化将引起信号在接收天线的到达角的变化,使信号衰落。这种现象使平均接收功率降低和使信号中断,从而使系统的可靠性和性能恶化。未来的数据网(FDN)要求改善国防通信系统(DCS)对流层散射和绕射电路,提供可靠的宽带数据通信能力。要求比特误码率(BER)随路径长度和所要求的利用率的不同 I. Introduction The propagation of over-horizon RF signals can be obstacle diffraction or tropospheric scatter. In the case of diffracted radiation, changes in the atmospheric refractive index cause the apparent antenna beam to bend up or down, resulting in the received signal weakening and fading out. For tropospheric scatter propagation, a change in the atmospheric refractive index will cause a change in the signal’s arrival angle at the receiving antenna, causing the signal to fade. This phenomenon reduces the average received power and interrupts the signal, thereby degrading system reliability and performance. Future Data Networks (FDNs) call for improving the DCS of the tropospheric scatter and diffraction circuitry to provide reliable broadband data communications. The required bit error rate (BER) varies with the path length and the required utilization