Research On Polarization Characteristics Of VLF Signals

The study of VLF propagation characteristics has important reference value for improving navigation and submarine communication technology.The amplitude characteristics and the polarization ellipse parameter characteristics of the VLF signal during the propagation process were analyzed statistically,and the polarization characteristics of the VLF signal during the diurnal transition zone were analyzed separately.The main work is as follows:1.It was found that:During sunrise,the amplitude characteristic curve presents maximum and minimum structure.The maximum appeared earlier than the sunrise time,and the minimum appeared later than the sunrise time.With the change of observation date,the Angle between signal propagation path and morning line becomes smaller,and the time difference between sunrise time and minimum time becomes larger.2..According to the statistical results of the calculated polarization ellipticity,the polarization state of VLF signals in daytime is mainly a fairly linear left-rotation or right-rotation polarization ellipse,and the polarization state in daytime is stable,with the ellipticity between-5 degrees and +5 degrees.The polarization state of VLF signals at night is mostly dextral polarization ellipse,but the polarization state at night is unstable,and the polarization ellipse fluctuates greatly3.The polarization ellipse parameters of 19.8khz signal in the diurnal transition zone were calculated,and the regularity of the polarization state changes of very low frequency electromagnetic waves in the two diurnal transition zones was found from the ellipse data.The rotation direction of the polarization ellipse would change from left to right,and the roundness and flat degree of the polarization ellipse would reach the maximum at a certain moment.The analysis based on waveguide mode theory agrees with the experimental phenomenon.