各向同性电离层低频一跳天波时延特性研究

Study on Time Delay Characteristics of Low Frequency One-hop Sky Waves in the Isotropic Ionosphere

低频天波的准确预测对于低电离层探测、远程导航授时具有重要意义。该文基于传统"波跳"理论和FDTD方法对地-电离层波导中天波传播时延特性进行研究。结合天地波时域分离技术,给出了100 kHz载频罗兰-C信号在均匀/指数渐变各向同性电离层条件下,距发射台200 km范围内采用两种方法计算的一跳天波时延随收发距离的变化规律。与"波跳"理论相比,该方法可同时考虑地面不规则、电离层昼夜参数分布不均匀的影响,计算精度更高。

Accurate prediction of low-frequency sky-wave has significance for the lower ionosphere detection and remote navigation timing. The characteristics of sky-wave propagation time delay in the Earth-ionosphere waveguide are studied in this paper based on the traditional wave-hop theory and FDTD method. Time delay variations of 100 kHz one-hop sky waves are given under homogeneous/exponentially graded isotropic ionosphere waveguide models. The great-circle distance between the transmitter and the receiver is within 200 km.Together with a sky-and ground-wave separation technique in the time domain, the narrow-band Loran-C signals are employed in two methods. Compared to the results of wave-hop theory, the method in this paper has higher calculation accuracy by considering the influence of irregular earth and inhomogeneous distribution of ionospheric day-night parameters at the same time.