一种数字电离层测高仪系统中O波与X波的分离方法

电离层测高仪系统中，O波与X波的分离非常重要.本文提出一种新的O波与X波分离的实现方法，根据电离层回波的极化特性，通过在接收电路上采用数字方法合成圆极化波的方式，实现了对O波与X波的有效分离.与现有DPS-4测高仪系统采用模拟域电信号合成圆极化波的方法相比，本文方法通过在数字下变频处理过程中引入±90°相移，消除了在模拟域电信号合成方法中相移器的带宽限制和非线性问题.另外，该方法在实现发射和接收信号的极化状态转换时不需要连续切换多个模拟开关，从而提高了整个系统的稳定性. 

A method for separating O wave and X wave in digital ionosonde

Separation for O wave and X wave is an important job in ionosphere detection. A new digital method for separating O wave and X wave is presented in this paper, being different from using image recognition technique to separate trace O and trace X in ionograms or electrical method to synthesize circularly polarized signals to separate O wave and X wave from echoes of the ionosphere. A numerical synthesizing method is employed in the new method. By introducing phase shifters of ±90° in digital domain, circularly polarized signals are synthesized digitally within the range of 1～ 30MHz, which eliminates the nonlinearity and expands the bandwidth of the ionosonde compared with DPS-4, and there is no need to switch the analog switches continuously. The new method has been successfully applied to CAS-DIS ionosonde and testing results show that the new digital method is capable of separating O wave and X wave well.