HF信道的色散带宽及其对脉冲波传播的影响  

Dispersive bandwidth for HF channel and its effects on pulse propagation

作　　者：种衍文[1] 黄天锡[1] 赵正予[1] 谢树果[1] 

机构地区：[1]武汉大学电子信息学院,湖北武汉430072

出　　处：《电波科学学报》2001年第3期394-397,408,共5页Chinese Journal of Radio Science

基　　金：国家自然科学基金(4990 40 10 );国家教育部博士点基金资助项目(RFDP19990 486 0 2 )

摘　　要：电离层是时变色散媒质 ,色散带宽是描述 HF信道色散程度的物理量 ,它完全由电离层的特性决定。文中采用 Lin等人给出的色散带宽的定义 ,将电离层电子浓度剖面进一步推广到球面分层 ,并给出计算球面分层、各向同性的电离层的色散带宽的普遍关系式。以电离层电子浓度剖面为准抛物层为例求解了色散带宽及其同收发间距和发射频率的关系。计算结果表明当收发间距 D>0且发射频率 f<MUF时 ,射线分为高角射线和低角射线 ,对应存在两个色散带宽。对应于每一个 D,存在一个最大可用频率 ( MUF) ,高角射线和低角射线会发生重合 ,色散带宽相等。高角射线穿入电离层较深 ,其色散带宽小于低角射线的色散带宽。提出并通过模拟计算证实了从信号恢复的角度看存在一个最佳的色散带宽 ,即高。The ionosphere is a dispersive medium which can lead to the distortion of a pulse. Dispersive bandwidth can be defined as that at which the amplitude spectrum is decayed to 1/e. It is completely characterized by the propagation channel and results from the dispersive properties of the propagation medium. By neglecting the geomagnetic field and plasma collision we gained the formulae of the dispersive bandwidth under the assumption of a spheric earth and ionosphere. Taking a QP layer as an example we present the curves to show the behavior of the computed dispersive bandwidth. For a fixed ground distance, the dispersive bandwidth is not zero at a frequency equal to the maximum usable frequency (MUF). As the normalized frequency F=f/fc is greater than1, the dispersive bandwidth is split into two:one corresponding to the high ray and the other corresponding to the low ray; the high ray has a lower dispersive bandwidth compared with the low ray. Complexity associated with modelling of electrical signals at the reception site after reflection from the ionosphere has been a challenging problem. In this paper we show the effects of HF channel characteristic parameters on signal modelling and pulse dispersion. From the view of restoring a signal there should be a best dispersive bandwidth at which the high ray and the low ray coincides with each other. In future study could be advanced by including the more perfect channel model and parameters.

关 键 词：色散带宽 电离层球面分层 脉冲波传播 高频信道 电波传播 

分 类 号：TN011[电子电信—物理电子学]