The Real-time Angle Measurement Bias Estimation Algorithm For Low-elevation Target Tracking

The radar system is an important method to identify the enemy aircraft and cruise missile. It has a great significance in the protection of the homeland security, and has attracted the world-wide attention in recent years. With the development of the digital signal processing techniques, the performances of the radar system have been hugely improved. However, in the case of tracking low-elevation target, the performances of the radar system are deteriorated due to the multipath interference. For steadily tracking target, we need to suppress the multipath interference. The off-axis tracking technique is one of the most common used anti-multipath methods. The basic idea of the off-axis tracking technique is to make the axis of the antenna rotate an extra angle to compensate the effect of the multipath interference. The extra rotated angle is called the angle measurement bias. The instability of the angle measurement bias has a negative influence on the target tracking process, and has been a barrier for improving the performance of the off-axis technique.In this study, we first discuss the geometric modeling of the radar multipath effect and analyze the relationships between the different physical quantities. On this basis, the estimation algorithm of the angle measurement bias is proposed. The angle measurement bias estimation algorithm is based on least square. We test performance of the angle measurement bias estimation algorithm by the simulation experiments. The results of the theory experiment indicate that the proposed algorithm can improve stability of the angle measurement bias and realize the stale tracking of the target.The main content of this study is summarized as follows:1. We first discuss the geometric modeling of the radar multipath effect and analyze the relationships between the different physical quantities. According to the differences in the properties, the multipath interference is divided as specular reflection wave and diffuse reflection wave. The characteristics of the specular reflection wave and diffuse reflection wave are investigated. On this basis, the influence of the multipath interference on the performance of the radar system is analyzed by taking the mechanism of the radar system into consideration. Furthermore, the necessity of suppressing the multipath interference is also discussed.2. The realization processes of the single-input recursive least-square method and the multiple-input recursive least-square method have been discussed. On this basis, we compare the performances between these two algorithms. The results show that the multiple-input recursive least-square method is superior to the single-input recursive least-square method. By considering the situation of the radar system, the multiple-input recursive least-square method is introduced into the field of angle measurement bias estimations.3. For suppressing the multipath interference, we propose an angle measurement bias estimation algorithm. The estimation algorithm is based on the least square algorithm. We assume that the previous angle measurement bias estimations have influence on the current angle measurement bias estimation result. By considering the previous estimation values, the current angle measurement bias estimation is obtained. In the algorithm, we use a fading memory index to control the effect of the previous angle measurement bias estimations. We use the theory experiment to check the performance of the angle measurement bias estimation algorithm. The results indicate that the proposed angle measurement bias estimation algorithm can get stable angle measurement bias estimations and obviously improved the performance of the off-axis technique.