天基预警雷达空中目标回波建模与分析

Modeling and analysis of air target echo for space-based early warning radar

针对天基预警雷达卫星平台和空中目标之间存在复杂相对运动的特点,首先建立了平台与目标的相对运动模型,推导并证明了平台与目标间存在等效的径向速度和加速度,在短时间内,它们的相对运动模型可以近似为匀加速运动模型;然后在匀加速运动模型的基础上,建立了空中目标回波模型;最后对回波模型进行了仿真.仿真结果表明,在短时间内,通过二阶多项式拟合的径向距离和实际径向距离之间的误差非常小,进一步验证了用匀加速运动模型来近似卫星平台与空中目标相对运动的合理性.此外,卫星平台与目标间的等效径向速度和加速度较大,在一个相干积累时间内,回波包络峰值存在较明显的跨距离单元徙动,直接利用动目标检测(MTD)技术对回波进行相参处理,会因信号能量散焦导致相参积累增益降低.

In view of the complex relative motion between the satellite platform of the space-based early warning radar system and the air target, this paper first establishes a relative motion model for the platform and the target, and deduces and proves that there exist equivalent radial velocity and accelerated velocity between the platform and target, and that in a short time their relative motion can be approximated as a uniform acceleration motion. And then based on the uniform acceleration model the paper establishes an air target echo model. Finally, a simulation on the echo model is done, and the result shows that in a short time, the error between the radial dis- tance fitted by the second-order polynomial and the actual radial distance is very small which further validates the rationality of using uniform acceleration motion model to approximate the relative motion of the satellite platform and the air target. In addition, due to the large equivalent radial velocity and acceleration between the platform and the target, there is a obvious range migration of the target echo peak envelope during a coherent accumulation time. Directly using the moving target detection technology to perform the phase-parameter processing on the echo, the coherent accumulation gain will decrease due to defocusing of the signal energy.