Research On Flying Target Altitude Estimation In High Frequency Ground Wave Radar

High Frequency Ground Wave Radars (including monostatic radar and bistatic radar HFGWR) are the only long range ground based radar systems that can detect targets at distances of up several hundreds of kilometers. As a result of the low attenuation over salt water of vertically polarized high frequency radio waves, HFGWR is capable of over-the-horizon real-time detection of low flying targets with 2-dimension observation information with the lack of altitude information. This paper proceeds thoroughly of theories analysis based on this background, and researches on the key technique of monostatic(bistatic) HFGWR to acquire the altitude information and construct 3-d information field, improve the monitoring and early warning ability, expand the scope of application. The primary contents are as follows:Firstly, the paper researches on the basic principles of monostatic HFGWR and the algorithm of altitude estimation. In this paper, the target echo intensity, propagation attenuation model and characteristics of target are simply analyzed. Both the detailed introduction of extended Kalman filtering and the nonlinear filtering algorithm are given. Besides that, the primary principle of bistatic radar is analyzed and the method of altitude estimation is proposed.Secondly, as for monostatic HFGWR, this paper mainly adopts the extended Kalman filtering algorithm. Auto regressive model is brought to the dynamic characteristic of target in order to estimate the RCS in real-time. Moreover the simulation results show that this method can improve the precision. As for the target of constant altitude flight, a new method is proposed. It makes use any section of flight status information to estimate the velocity and altitude. This method is argued for its high precision and simplicity.At last, as for bistatic HFGWR, because of the redundancy of the measured data, the altitude is estimated using different measurement subset. Before using redundant information, the single measurement subset is presented to calculate the GDOP, and then improve the performance of target altitude estimation using WLS and SWLS algorithm to combined estimate. In order to reduce calculation, it proposes a way of partitioning that in different regions use different measurement subset. Considering the inevitable estimated bias, due to curvature of the earth for long distance target detection, a measurement of the correction is supplied.