A Method for Separating O-Wave and X-Wave of Ionosonde Based on Dual-Channel Phase Difference Statistics

The echo signal received by ionosonde contains both ordinary wave (O-wave) and extraordinary wave (X-wave), and its separation result directly determines the accuracy of mode discrimination and ionospheric parameter inversion, which is of great significance to ionospheric research. The separation of O-wave and X-wave is exceptionally complex due to environmental noise, instrumental thermal noise, external interference, and the time-varying dispersion properties of the ionosphere itself. In this article, a method for separating O-wave and X-wave of ionosonde based on dual-channel phase difference statistics is proposed, which uses constant false alarm rate (CFAR) detection to extract the vertical ionospheric measurement echo signals and dynamically calculates the compensated phases of O-wave and X-wave separations at each frequency, achieving the robust and effective separation of O-wave and X-wave. The results of the measured data show that: 1) this method dynamically calculates the phase compensated for O-wave and X-wave separation by considering the variation of the compensation phase with frequency and time, through real-time statistics of the phase difference in the echo signal; 2) it compensates for the amplitude difference between the two channels and the signal-to-noise ratio of the separated O-wave and X-wave is improved; 3) it exhibits strong robustness and is suitable for vertical ionospheric signals in various modes; and 4) it demonstrates good performance, with the accuracy of O-wave and X-wave separation reaching 98.64%, which is 21.37% higher than the traditional dual-channel phase compensation methods.