【作者】 邓斌；

【导师】 黎湘；

【作者基本信息】 国防科学技术大学 ， 信息与通信工程， 2011， 博士

【摘要】 研究利用单一信号形式实现多种功能的新体制雷达具有迫切的军事需求和现实意义。论文围绕多载频相位编码雷达信号的设计与处理技术进行研究,重点开展多载频雷达信号设计、脉冲压缩与目标检测、运动目标参数估计与成像三个方面的研究工作。论文首先介绍了多载频雷达信号的来源与分类,从信号包络和模糊函数两方面研究其特性。针对多载频相位编码信号结构灵活的特点,分析了不同子载频加权方式对信号包络峰均比的影响;理论推导完整的模糊函数表达式,分析其自相关函数与信号各参数之间的关系,为信号设计提供了理论基础。针对多载频雷达信号的参数设计与优化问题,首先以模糊函数作为优化准则,对信号参数相对较少的OFDM信号进行参数优化,设计出的信号自相关函数旁瓣水平极低,适合进行目标探测。然后针对MCPC信号模糊图整体旁瓣较高的问题和现有信号设计方法的局限,提出了一种随机移位编码的MCPC信号,并通过时频域限幅迭代方法有效降低其包络起伏,在模糊图和包络控制方面同时取得了令人满意的性能。这种设计方法可以很方便的生成具有波形分集特点的脉冲串信号,具备十分理想的模糊函数和较低的周期性自相关旁瓣。最后分析了多载频雷达系统性能参数,以此指导发射波形参数的设计,并结合具体任务给出了设计实例。针对MCPC雷达回波在脉冲压缩中的计算效率问题和对多载频结构的充分利用,基于子载频分离的思想,在时域分码元进行处理,推导两级脉压的过程,针对子载频未作加权的一类特殊MCPC信号给出带宽合成的快速脉压方法;针对加权后的MCPC信号提出了改进的子载频合成滤波方法,有效降低其计算量。然后为了避免时域分段错位现象,给出了频域脉压方案。在改变DFT快速算法计算顺序的基础上提出了频域分段匹配法,在不增加计算复杂度的前提下很好地实现了子带的分离与合成,能够同时获得粗分辨积累距离像和高分辨距离像。最后给出脉冲串信号的脉压方法并综合比较了各方法的脉压性能和计算量。针对MCPC雷达目标检测问题,在两级脉压的基础上针对高分辨距离像给出了宽带检测方法,针对粗分辨积累距离像则提出了基于窄带框架的检测方法。对于脉冲串信号,所提出的方法在脉间通过相参积累保证信噪比增益,在载频间通过非相参积累保证目标散射点能量的良好聚集。仿真实验表明了窄带框架下的检测方法在高速动目标检测上的优势。针对MCPC雷达运动目标参数估计问题,基于随机移位相位编码的MCPC脉冲串信号,分析其模糊函数低旁瓣在消除距离周期性模糊上的作用,给出测距原理和仿真实验。针对当前宽带雷达在测速时面临的高分辨距离单元走动问题与速度模糊问题,基于子载频多普勒处理技术,提出了基于最小二乘法的速度解模糊方法,将速度测量的适用范围提高到积累时间内目标走动不超过一个粗分辨距离单元,并针对低速、中高速和高速运动目标,分别给出仿真实验和测速性能。基于Radon-CLEAN方法实现了多目标速度分辨,能够在低信噪比条件下对高速运动目标进行速度分辨与高精度测量。针对MCPC雷达高速运动目标ISAR成像问题,用实时估计的速度和距离为ISAR成像提供运动补偿和参考距离,提出了利用多个脉冲串进行ISAR成像的算法和宽带雷达多功能一体化的实现框架。针对高速运动目标,分析了成像时遇到的相位误差和散射点越距离单元走动问题,根据仿真数据进行了成像实验,与LFM雷达在ISAR图像质量上做了对比。仿真结果表明,利用前端测速结果进行运动补偿后的MCPC雷达在ISAR成像上更有优势。更多还原

【Abstract】 It is of pressing military demands and practical signality to research utilizing single form of signal to realize new type wideband radar with multiple functions. The dissertation focuses on the research of signal designing and processing of multi-carrier phase coded (MCPC) radar. Three main subjects are addressed in this dissertation, which are designing of multi-carrier radar signal, pulse compression and target detection as well as parameter estimation and imaging of moving target.The derivation and category of multi-carrier radar signal is firstly addressed whose envelope and ambiguity function (AF) are two main characteristics. Based on the flexibility feature of MCPC, the impact of different sub-carrier weighting on signal envelope is analyzed. And the full expression of AF is deduced to research the relationship between auto cross function and signal parameters, which provides theoretical basis for signal designing.For the parameter designing and optimization of multi-carrier radar signal, based on the rule of AF, the OFDM signal with relatively less parameters is firstly designed to achieve very low sidelobes in ACF, which is suitable to target detection. Secondly, considering the high sidelobes in AF of MCPC and the drawback of current designing method, a random shifted phase-coded MCPC is proposed. Its envelope is efficiently lowered by time-frequency clipping iteration which leads to satisfied ambiguity diagram and envelope fluctuation at the same time. This method is able to expediently produce waveform-diverse pulse train with ideal AF and low recurrent sidelobes in ACF. Finally the multi-carrier radar system performance is analyzed to instruct the designing of transmitting waveform and designing samples towards specific mission are given.For the computational efficiency and full usage of multi-carrier structure in pulse compression (PC) of MCPC radar echo signal, based on sub-carrier separation, signal chips are firstly divided in time domain. Two-level PC process is deduced to efficiently compress a special kind of MCPC without sub-carrier weighting. And improved wide band synthetic filtering is proposed to lower the calculation amount when compressing MCPC with sub-carrier weighting. Afterward PC methods in frequency domain are addressed to avoid improper chip dividing problems. By changing the computing order of FFT, piecewise matching method in frequency domain is brought forward to realize separation and synthesis of sub bands without growing computational complexity. It is able to obtain integrated coarse resolution range profile (CRRP) and HRRP simultaneity. Finally the PC of pulse train is given. Also the performance and calculation amount are compared among different methods.For the target detection in MCPC radar, on the basis of two-level PC, wideband detection method is addressed upon HRRP. And a detection strategy based on narrow band frame is proposed upon integrated CRRP. For pulse train signal, this method guarantees SNR gain through coherent integration among pulses and obtains favorable energy gathering of scattering points through non-coherent integration among sub-carriers. Simulations indicate the advantage of detection method based on narrow band frame when detecting moving target at high velocity.For the parameter estimation of moving target in MCPC radar, based on random shifted phase-coded MCPC pulse train, its low AF sidelobes is utilized to eliminate recurrent range ambiguity. Distance measurement principle with simulations is then provided. While nowadays wideband radar faces the range walk of HRRP cells and velocity ambiguity problems, LSE method based on Doppler processing of sub-carriers is proposed to solve velocity ambiguity. This method promotes the suitable scope of velocity measurement to one CRRP cell that target walking through in integration interval. Experiments are given toward target moving at low, medium and high velocity respectively. Velocity resolution based on Radon -CLEAN is then brought forward and proved to distinguish targets with diverse speed against low SNR.For the ISAR imaging of fast moving target in MCPC radar, using the real-time estimated velocity and range as motion compensation and reference distance, an ISAR imaging method based on multiple pulse trains and multi-functional wideband radar in integrative frame are proposed. The phase error and scatter migration through resolution cell problem when imaging the fast moving target is discussed and the ISAR result is compared with LFM radar. Simulations present the advantage of MCPC radar in ISAR imaging after motion compensation by provided velocity.更多还原