The change trend of state variables,such as flight speed,velocity angle,longitudinal range,altitude,for hypersonic glide vehicle under the condition of skip glide are studied.The numerical solutions of the vehicle state variables are obtained with the fourth-order Runge-Kutta method.The numerical solutions of state variables are fitted with different order orthogonal polynomials,and the analytical solutions representing the variation trend of the state variables are solved.The simulation results show that the mean difference of the root mean square error (RMSE) of the three analytic solutions of flight speed,velocity angle and altitude is 20 m/s,0.1° and 1.5 km respectively,so the variation trend of flight speed,velocity angle and altitude under the skip glide condition can be expressed by the first order orthogonal polynomial.The RMSE of the first order analytic solution of the flight longitudinal range is obviously larger than that of the second order analytic solution and the third order analytic solution,so the flight longitudinal range under the skip glide condition can be expressed by the second order or the third order orthogonal polynomial.

In recent years, due to the emergence of military and civilian applications of the outbreak of growth, the unmanned aerial vehicles and light helicopters as the representative of the low-altitude slow small target has been rapid developed. Because such targets have the characteristics of “low flying altitude, slow flight speed and small RCS”, the target echo is often submerged in the strong ground/sea clutter. The traditional detection technology based on the frequency domain filtering is difficult to detect, which brings new serious challenge for the air defense early warning radar. To solve the problem, the multi path interference, atmospheric attenuation, system loss and other factors, the construction of the target echo model are considered; based on the strong clutter suppression by Kalmus filter, the distance and slow time image of the multi-frame radar echo data under long term observation is simulated by the slow time domain. After combining with the Radon transform, the target detection is completed through the threshold setting of the transformed parameter field. The experimental results show the effectiveness of the proposed method.

The major difficulties in early warning radar detection targets based on the analysis of the characteristics of low altitude slow and small target (LSS-target) are summed up, and several typical target detection technologies with great development potential are discussed based on TBD (track before detect) technology, transform domain analysis, micro-Doppler analysis, system detection,clutter whitening or other methods. The performance of each method is analyzed and some suggestions on the development of such target detection technology are put forward.