And then the stability and the stable error response of the dpll are analyzed . there is an obvious doppler shift frequency offset in the received signal with flight at a high speed , in the dissertation the uniform sampling second - order dpll is used to remove the frequency bias for its excellent high - pass characteristic of the error transfer function 由于高速飞行的遥测目标在接收信号中会出现较大的多普勒频率分量,而典型均匀采样二阶数字锁相环dpll ( digitalphase - lockedloop )的误差函数具有高通特性,所以本文提出一种利用其高通特性来去除多普勒频率分量的新方法。
Due to the short distance among the planes which fly in a group , the conventional low resolution radar can not distinguish them in both distance and azimuth ? if we use the technology of isar to resolve the difference among doppler frequency of the targets and obtain a fine resolution cross - cross image , we may separate them , but a long time of coherent processing is needed < , for the formation targets , it can be approximately divided to rigid body and nonrigid body , so for the formation targets , that can be regarded as rigid which has a relative position and an identical movement , can be approximately considered as a large target , and be compensated by translational phase with the rule of minimum entropy , but for the most those cannot accord with the approximation of rigid , being the doppler - frequency of the aim is linear changed , by the relax method with short data , increases the resolving performance of multiple target to the aim in the frequency domain , since cross - range resolution is based on the accumulative time , so it is greatly improve the resolution to formation targets by the instant cross - range image which produced by radon - wigner transformation 低分辨isan成像及干涉技术应用研究一因此直接无法分辨编队目标的架数，我们借鉴isar的技术，通过较长时间的相干积累，在多普勒频域上对目标进行分辨。而对于编队目标，可分为近似刚性的多目标和非刚性的多目标，所以对于可以近似为刚体的编队目标相对位置固定，运动方式一致，可以近似看作一个大目标，采用最小墒准则对平动相位的进行补偿，但是大多数并不满足刚体近似的编队目标，由于目标在相干积累时间的多普勒频率近似呈线性变化，通过对较短数据利用relax的时频分析方法，提高了频率域上目标分辨的性能。由于横向分辨率取块于横向积累时间，所以利用radnwigner变换得到瞬时的一维横向距离像大大提高了对编队目标的分辨，对仿真和实测数据的大量分析结果表明此方法的有效性和可行。
The major work is as following : based on the analysis of signal receiving problems when navigation receiver is in high dynamic circumstance , some typical algorithms such as maximum likelihood estimator ( mle ) , extended kalman filter ( ekf ) , frequency lock loop ( fll ) , digital phase lock loop ( pll ) and frequency extended kalman filter ( fekf ) are deduced 高动态下面临着多普勒频率、多普勒频率变化率较大的问题,给载波跟踪带来了很大困难。本章分析了目前高动态接收机中普遍采用的几种载波跟踪算法,对算法的性能进行了比较。
Space - borne radar parameters are used in simulation . base on the doppler frequency of rebound jamming signal , along - track interferometric detection scheme , which is proposed in chapter 4 , is employed to detect point target rebound jamming in simulation , and the results validate the feasibility of this kind detection scheme . at last , a detailed comparison between rebound jamming and false target jamming is made 第五章介绍了弹射式干扰原理,对干扰信号特征及干扰效果作了具体的分析,并利用机载sar参数作了干扰仿真实验;根据弹射式干扰信号多普勒频率的特点,利用沿航迹双天线干涉对消技术对弹射式点目标干扰进行检测,分析了仿真结果;最后还将弹射式干扰与虚假图像干扰进行了比较。
As the targets flying in groups may spread over several range of cells and their doppler frequencies are time * . varying , a scheme of target number detection in groups on a conventional low * . resolution radar is proposed based on a time * . range * . doppler image cube which is constructed by substituting a time * . frequency transform for the fourier transform in the conventional range * . doppler imaging 针对实际编队目标在距离上的分布特性和目标多普勒频率的变化规律，利用联合时频变换代替传统傅立叶变换，建立目标时间-距离-多普勒立体像，提出一种基于立体像的目标架次检测方法。
For slow targets whose doppler frequencies fall into clutter doppler band , the performance of frequency domain one - dimension filtering is seriously degraded . in an airborne radar , there is interdependence between the clutter doppler frequency and spatial position . space - time adaptive processing ( stap ) utilizes this interdependence to suppress clutter and get perfect main - lobe and side - lobe clutter suppression 空时自适应处理利用机载雷达地杂波多普勒频率与地杂波空间位置的耦合性,根据目标和杂波在空间-多普勒频域二维空间分布上的差别对杂波进行抑制。
Quite a few of new methods of soplat have been proposed in the last decade , most of these methods add new measurements values to the bearing - only method base on the particle kinematics . this paper studies the challenge technology of soplat method using frequency rate , including frequency and frequency rate estimation 近几年来,这一技术得到了新的发展,质点运动学原理和多年的研究证明,在传统的只测向方法的基础上增加多普勒频率变化率的算法可提高无源定位系统的可观测性,实现瞬时定位,但同时也对信号接收机提出了更高的要求。
The specific research methods are listed : 1 . matched filter taking the max ouput snr as the best rule correlates nonstop divided signal and divided echo to detect low snr target signal . then all one dimension divided correlation outs and done fft in portrait to leach interferential signal such as static or low rate mussy meaves , many pathway echo and so on and to take target ' s time difference and doppler frequency that combine parameters that target ' s direction taken from antenna and so on to implement target ' s orientation and tracking 具体研究方法如下： 1 、采用以输出信噪比最大为准则的最佳匹配滤波器来对分段的参考和目标信号作相关处理来检测低信噪比目标信号，然后对一维分段相关输出组作纵向傅立叶变换来滤除静态或低速的杂波、多径回波等干扰信号，并提取目标的时差和多普勒频率，再结合由天线获得的目标方向等参数，就可以实现目标的定位和跟踪。
In this dissertation , the common choices of spotlight mode sar image formation , such as pfa and rma , as well as new emerging methods like wpfa and dda , are discussed in a heuristic and comprehensive way , provided with the simulation illustrations and real data proccessing results . each algorithm processes unique capabilities and limitations that determine its applicability for specific sar systems and missions 本文讨论了聚束模式信号处理中广泛应用的极坐标格式算法( polarformatalgorithm , pfa )和距离徙动算法( rangecellmigration , rma ) ,以及新出现的大场景极坐标格式算法( widefieldpolarformatalgorithm , wpfa )和差分多普勒频率算法( differentialdoppleralgorithm , dda ) 。
