【作者】 袁振涛；

【导师】 郁文贤； 胡卫东；

【作者基本信息】 国防科学技术大学 ， 信息与通信工程， 2009， 博士

【摘要】 近地轨道空间是关系国家安全的重要领域,也是经济建设的重要资源。伴随着空间目标运行环境的不断恶化,对空间目标进行系统性的监测已经刻不容缓。空间目标普测型雷达作为目标广域探测、捕获的基础性设备,在空间目标监测体系中具有重要的地位。本文针对宽波束驻留类的空间目标普测型雷达在信号处理和数据处理中的多项关键技术进行研究,开展的工作和取得的成果包括下面几个方面。首先,研究了空间目标相对于测站的运动特征,推导出空间目标相对于测站的运动参数的计算表达式,讨论了轨道偏心率对目标运动参数计算的影响。在此基础上,针对宽波束驻留类普测型雷达,给出了已知轨道根数空间目标的运动参数计算流程,建立了该类型雷达的回波信号模型,即目标回波为线性调频(LFM)信号。之后,从信噪比(SNR)积累增益的角度出发,研究了常用的基于快速傅立叶变换(FFT)的动目标检测方法在空间目标检测中的性能和适用范围。然后,开展了基于分数阶傅立叶变换(FrFT)的目标检测与运动参数估计的研究。在给出基于FrFT的LFM信号检测与参数估计流程以及离散型DFrFT的计算过程后,从理论上研究了离散型DFrFT在高斯白噪声下对LFM信号的SNR积累增益与参数估计精度。在对离散型DFrFT的分辨率进行分析后,研究了利用离散型DFrFT对LFM信号处理时造成峰值点搜索偏差的因素,提出了利用内插DFrFT实现LFM信号参数估计的方法。该方法突破了由信号时宽带宽积决定的u域(即分数阶傅立叶域)分辨率的限制,提高了算法对LFM信号参数的估计精度,通过仿真计算验证了算法的有效性。此外,时频平面内的旋转角度α对峰值点搜索也有影响,并对系统处理的实时性起着决定作用。因此,针对空间目标监测这一具体应用,文中还对参数α的搜索区间及搜索间隔的确定进行了研究。其后,研究了利用阵列天线实现空间目标到达角(DOA)估计的方法。空域矩阵滤波器通过保持空域通带内的信号,并抑制空域阻带内的干扰与噪声来提高DOA估计的性能。为消除空域矩阵滤波作用后产生的高斯色噪声的影响,进一步地提高对信号源DOA估计的性能,提出了基于四阶累积量的空域矩阵滤波DOA估计算法。分析表明,利用四阶累积量对高斯噪声的不敏感性,该方法能够提高子空间类算法在低信噪比条件下的DOA估计性能,并能够抑制高斯色噪声对子空间类DOA估计算法的影响。此外,通过滑动空域矩阵滤波器的空域通带,使得该方法具有估计出多于阵元个数的目标DOA的能力。之后,将该方法改写为迭代形式来校正阵列通道幅相误差。通过仿真计算对算法的有效性进行了验证。最后,对多目标同时穿越雷达视场时的测向数据关联进行了研究。以宽波束驻留类普测型雷达的空间目标位置确定为研究对象,建立了多接收站数据关联的数学模型。之后,推导出空间目标相对于各接收站距离变化率的计算表达式,并在目标运行于圆轨道的假设下,推导出利用接收站获取的多普勒频率信息得到空间目标轨道倾角的计算过程。利用各接收站计算得到的空间目标轨道倾角,构建代价函数,提出了利用轨道倾角差进行多接收站测向数据关联的方法。该方法仅利用两接收站获取的测量值进行数据关联,不需要为增加空间冗余信息而增设接收站,很好地解决了测向数据的关联问题。文中还分析了多普勒频率测量误差、角度测量误差以及轨道偏心率对轨道倾角计算的影响,并通过仿真计算验证了算法的有效性。更多还原

【Abstract】 The near earth space is a crucial area for the national security as well as an important resource for the economy development. As the degradation of operating environment for the spacecrafts, it is extremely urgent to realize exhaustive space objects surveillance. As the basic instrument for wide-field space objects detection, the general survey type radar plays a very important role in space surveillance system.Some key techniques in signal processing and data processing of the“wide resident beam”radar, which is a kind of general survey radar, are studied in this dissertation. The main studies and the contributions can be summarized as follows.Firstly, the motion characteristics of space objects with respect to the survey station are studied. The analytical expressions of motion characteristics are derived, and the effects caused by the eccentricity are also discussed. For the application of“wide resident beam”radar, the movement characteristics calculation for space objects with known orbit elements is obtained and the model of radar echo signal is founded. From the point of view of output SNR (signal noise ratio) gain, the performance and applicability of FFT (fast Fourier transform), which is a common moving target detection technique, are analyzed.Secondly, the space objects detection and parameters estimation are studied. At the beginning, the principle of LFM (linear frequency modulated) signals detection and parameters estimation based on FrFT (fractional Fourier transform) are summarized. Then, the detection performance and estimation accuracy are analyzed theoretically where LFM signal with WGN (white Gaussian noise) is processed by discrete type DFrFT (discrete fractional Fourier transform). The factors which cause the error in“peak searching”are analyzed when DFrFT is applyed. The results show that the resolution of DFrFT in FrF (fractional Fourier) domain is the dominating one. For solving the finite FrF resolution which is determined by the time-bandwidth product of the signal, a novel approach using DFrFT interpolation is proposed. Using DFrFT interpolation, the method breaks through the FrF resolution and gets higher accuracy of parameters estimation. The results of simulation validate the effectiveness of this approach. The rotation angleαin time-frequency plane affects the“peak searching”as well as the computation complexity, therefore, the rotation range and interval of angleαare also analyzed.Subsequently, the DOA (direction of arrival) estimation of space objects with antenna array is studied. As an implementation of spatial filtering, the spatial matrix filter (SMF) improves the performance of DOA estimation of multiple sources through keeping the signals in spatial passband (sector-of-interest) and attenuating the noise and interference in spatial stopband (outside the sector-of-interest). To eliminate the effects caused by SMF, a novel approach based on the fourth-order cumulant (FOC) of the data snapshots is proposed. As the fourth order cumulant of Gaussian noise is zero, this approach is capable of improving the performance of DOA estimation in lower SNR or CGN (colored Gaussian noise) situations. Meanwhile, by sliding the passband of SMF, the approach makes it possible to estimate DOAs of multiple sources with a number more than the array elements. Moreover, the approach is rewritten in an iterative form to calibrate the channel gain and phase error of antenna array. Results of simulation verify the approach’s validity.Finally, the techniques are investigated to solve the problem of direction data association when multi-targets cross the radar FOV (field of view) synchronously. Towards the position determination problem of“wide resident beam”radar, the model for multi-receiver data association is established at first. Then, the expression of the range rate of space objects with respect to the receiver is derived. Under the assumption that the orbit of space objects is circular, the calculation of inclination using the Doppler measurements is derived. Considering the difference of DI (Doppler inclination) and effects caused by false and miss alarm, the cost function for direction data association is founded. This approach just use the measurements acquired by two receivers to achieve direction data association, so there is no need to set up other receivers for acquiring redundant direction data. At last, the effects caused by the eccentricity and the measurement error on DI calculation are analyzed. The feasibility and validity of this approach is validated by the simulation.更多还原