相参脉冲序列PRI变化率的高精度估计方法

在单站无源定位与跟踪系统中,PRI变化率信息反映了运动目标的径向加速度信息。提出了一种新的PRI变化率估计的算法,利用脉冲载频之间的相参积累,使信噪比得到提高,通过群延迟,使PRI的变化量得到积累,推导出一种快速而精确测量PRI变化率的算法,数值仿真证明使用该算法可以精确快速地估计信号中的PRI变化率信息。     

基于FrFT的LFM相参脉冲信号多普勒频率变化率估计算法

线性调频信号(LFM)在雷达中广泛应用,精确获取观测LFM信号中的多普勒频率变化率信息是单站无源定位与跟踪系统的一项关键技术。该文提出了基于分数阶Fourier变换(FrFT)的多普勒频率变化率估计算法,在分数阶变换域上使信号能量聚集,消除调频率对参数估计的影响的同时充分提高了信噪比,进而利用保留的脉冲间相对相位关系获得了多普勒频率变化率的高精度估计。理论分析表明,该算法估计精度接近理论下界,数值仿真验证了算法的有效性。     

基于相位补偿的BPSK相参脉冲串信号多普勒频率变化率估计算法

目标与观测平台之间径向加速度引起的接收信号多普勒频率变化率的精确估计对于高精度单站无源定位与跟踪具有重要意义。该文针对脉内相位调制信号的频率变化率不能直接表征多普勒频率变化率的问题,首先引入相位补偿的方法消除BPSK相位调制序列的影响,然后针对固定脉冲重复频率和脉冲重复频率抖动两种情况分别提出了径向加速度引起的多普勒频率变化率的精确估计方法,并且给出了多普勒频率变化率与采样频率、观测时间及脉冲重复频率之间的约束关系。仿真结果表明,典型参数条件下该文提出算法的信噪比门限比已有算法低约4~6 dB。     

一种PCM相参脉冲序列多普勒频率变化率估计算法

相位编码调制信号是一种典型的脉冲压缩信号,广泛应用于脉冲压缩体制的低截获概率雷达中。来波信号中多普勒频率变化率的高精度估计是基于质点运动学原理的单站无源定位与跟踪的一个关键技术。该文针对信号脉内相位调制和多普勒频率变化率信息非常微弱的特点,提出了一种快速高精度估计算法,通过相邻脉冲间的时域相关消除了相位调制对参数估计的影响,频域积累增强了信噪比,利用脉冲间的相参特性进行频谱相关消除了相位模糊,并放大了多普勒频率变化率信息。算法计算量小,为实际应用提供了良好条件。计算机仿真结果证明了算法的有效性。     

基于小波变换的多普勒频率变化率高精度估计方法

在单站无源定位与跟踪系统中,获取多普勒频率变化率信息对运动目标的状态估计和定位具有非常重要的意义.多普勒频率变化率非常微弱,很难精确测量.小波变换是一种时频局域化的分析方法,具有较低的信噪比门限.本文提出了基于小波变换的多普勒频率变化率估计方法,计算机仿真研究表明本文提出的方法具有较低的信噪比门限,并且可以快速精确地实现参数估计.     

LFM相参脉冲串多普勒频率变化率估计

在传统的只测向单站无源定位算法的基础上,增加波达角变化率和径向加速度两个观测量,可以大大改善定位与跟踪的性能,所以高精度径向加速度估计(即多普勒频率变化率估计)具有重要意义。由于在无源定位里没有接收脉冲信号的任何先验知识,接收到的LFM相参脉冲串信号的相参性容易被破坏。文中借鉴雷达里的匹配滤波方法,提出一种“准匹配滤波”方法,首先估计每个脉冲的到达时间、脉冲宽度、起始频率和调频系数,接着构造本地参考信号用于对接收信号进行“准匹配滤波”,最后对其输出进行多普勒频率变化率估计。该方法可以避免处理过程中的非相参问题,运算简单,估计精度高,具有应用价值。     

相参脉冲序列频率估计的小波变换方法

在单站无源定位与跟踪系统中,接收信号的多普勒频率变化率信息对运动目标的状态估计和定位非常重要。对于脉冲体制的雷达来说,信号持续时间较短,很难精确测量多普勒频率变化率。小波变换在时频域同时具有良好的局域特性和较低的信噪比门限。文章引入了小波变换方法实现单站无源定位与跟踪系统的参数估计,推导了相参脉冲序列的小波变换方法。数值仿真证明该方法能实现脉冲的相参积累,大幅提高参数的估计精度。     

一种基于两维信息联合处理的机动目标定位技术

对一种基于两维信息联合处理的机动目标定位技术进行了研究和论述,该技术通过同时测量目标信号的多普勒频率变化率和相位变化率,能够实现对机动目标的快速定位和速度估计。仿真结果验证了该技术的可行性和有效性。     

一种QAM信号多普勒参数盲估计方法

在卫星移动通信中,卫星相对地面接收站的高速运动导致接收信号存在时变多普勒频率,给正交幅度调制(QAM)信号的载波同步带来了极大困难.现有的多普勒参数估计方法多利用导频等先验信息,适用于移相键控(PSK)信号.但在估计多普勒频率变化率时假设多普勒频率较小,不符合实际情况,且现有方法无法估计较大的多普勒频率,另外在非协作通信下先验信息难以获得.对此,本文提出了一种针对高阶QAM信号的多普勒参数盲估计方法.将信号盲去调制后,利用瞬时频率估计函数,可在较大的多普勒频率下估计出多普勒频率变化率;通过检测信号四倍频率处的循环频率,实现了多普勒频率盲估计;最后利用arg运算求出初相.详尽的Monte Carlo仿真分析了方法的估计性能,仿真结果表明,所提方法能有效实现QAM信号的多普勒参数盲估计.     

一种脉冲群间多普勒频率变化率的估计算法

提出了一种脉冲群间多普勒频率变化率估计算法,该算法利用离散傅里叶变换进行脉冲间相参积累,获得脉冲群的相对模糊频率,通过脉冲群间相对模糊频率差分获得多普勒频率变化率。算法具有计算量小、多普勒频率变化率估计精度高的优点。计算机仿真结果证明了算法的有效性。     

制导激光编码信息识别技术研究

激光脉冲编码是半主动激光制导武器采用的一种抗干扰措施,为满足对抗半主动激光制导武器的需要,以激光信号的脉冲到达时间为参数,在分析现有各种码型及其识别方式的基础上,对激光脉冲编码信息逐次逼近,即在得到极少量的激光脉冲样本后,同步拟合解算不同码型参数,并结合模糊决策思想,预测下一脉冲的到达时刻,下达发射干扰脉冲的指令,同时侦测敌方目标指示器的后续脉冲到达时刻,在样本不断增长的过程中,对预测码型不断调整,逐步达到精确复制敌方编码信号的目的。试验结果表明,对常见的编码模式,该技术能通过较少的脉冲信息有效的识别脉冲编码规律。     

Optical Pulse Formats for Fiber Optic Digital Communications

Some new optical pulse formats are investigated for solving practical problems in fiber optic communication systems. These pulse formats provide many advantageous features such as error monitoring capability, abundant timing information, uniform optical power utilization, stable detection of optical input, and so forth. It is shown that a modification of Personick's receiver design theory can be used for comparison of various optical pulse formats. The comparison suggests that for state-of-the-art fiber systems with moderate fiber loss and moderate repeater spacing, where no pulse equalization is required, some new classes of 1 binary digit converted to 2 binary digits (1B2B) or 2B3B formats will permit the realization of very simple and reliable repeaters for fiber optic digital transmission. A future low-loss fiber system may permit a very long repeater spacing with the help of equalization. In this case, application of the correlative signal-processing technique is shown to be very promising. Experimental 6.3 Mbit/s and 100 Mbit/s transmissions demonstrate some advantageous features of these optical pulse formats.     

Time-resolved optical gating based on dispersive propagation: a newmethod to characterize optical pulses

We introduce the technique of time-resolved optical gating (TROG) based on dispersive propagation (DP), a new noninterferometric method for characterizing ultrashort optical pulses in amplitude and phase without the need for a short optical gating pulse. TROG is similar to frequency-resolved optical gating except that the role of time and frequency is interchanged. For the DP-TROG geometry, we show that measurements of the autocorrelation trace of the pulse after propagation through a medium with variable dispersion together with a single measurement of its intensity spectrum contain sufficient information to reconstruct the pulse in amplitude and phase. Pulse reconstruction for this DP-TROG geometry works very well even for the case of a nonlinearly chirped double pulse. Compared with other methods, DP-TROG does not introduce an ambiguity in the direction of time for the pulse. Due to its simplicity and improved sensitivity. DP-TROC is expected to be useful in characterizing low-energy pulses     

单脉冲雷达数据采集及处理方法

在载人航天、编目空间目标以及对战区导弹进行预防警报等方面单脉冲测量雷达有着极为重要的实用价值,而脉冲雷达的核心就是数据的采集与处理,数据采集与处理在脉冲雷达完成各项工作时发挥的作用是十分重要的.本文结合了进行研究的单脉冲测量雷达,对脉冲雷达关于数据处理方面的功能、结构组成、工作原理以及工作中使用的算法和实现的方法进行了系统的阐述.针对新型单脉冲测量雷达的一些关键特点进行分析.     

跳频扩频系统的Matlab模拟仿真实现

跳频扩频技术采用特定的扩频函数及载波跳变来实现频谱展宽,具有很强的抗干扰性,并具有信息隐蔽、多址保密通信的特点;PSK调制方式由基带脉冲控制载波相位。在Matlab／Simulink下建立了采用BPSK方式的跳频扩频（FH—SS）通信系统模拟模型,并编程仿真实现该系统,对跳频扩频通信的实现有重要意义。     

An advanced demultiplexing system for physiological stimulation

A CMOS very large scale integration (VLSI) chip has been designed and built to implement a scheme developed for multiplexing/demultiplexing the signals required to operate an intracortical stimulating electrode array. Because the use of radio telemetry in a proposed system utilizing this chip may impose limits upon the rate of data transmission to the chip, the scheme described herein was used to reduce the amount of digital information which must be sent to control a large quantity (up to several hundred) of stimulating electrodes. By incorporating multiple current sources on chip, many channels may be stimulated simultaneously. By incorporating on-chip timers, control over pulse timing is assigned to the chip, reducing by up to fourfold the amount of control data which must be sent. By incorporating on-chip RAM, information associated with the desired stimulus amplitude and pulse timing can be stored on chip, In this manner, it is necessary to send control information to the chip only when the information changes, rather than at the stimulus repeat rate for each channel. This further reduces the data rate by a factor of five to ten times or more. The architecture described here, implemented as an eight-channel stimulator, is scalable to a 625-channel stimulator while keeping data transmission rates under 2 Mbps     

Time reversal with the FDTD method for microwave breast cancer detection

The feasibility of microwave breast cancer detection with a time-reversal (TR) algorithm is examined. This algorithm is based on the finite-difference time-domain method, and compensates for the wave decay and, therefore, is suitable for lossy media. In this paper, we consider a two-dimensional breast model based on magnetic resonance imaging data, and examine the focusing abilities of a TR mirror comprised of an array of receivers with a single ultra-wideband pulse excitation. In order to resolve small 3-mm-diameter tumors, a very short duration pulse is necessary, and this requirement may restrict the applicability of the system due to hardware limitations. We propose a way to overcome this obstacle based on the observation that the amplitude and phase information of the tumor response is sufficient to achieve focusing. The robustness of the TR algorithm with respect to breast inhomogeneities is demonstrated, and the good performance of the method suggests it is a promising technique for microwave breast cancer detection.     

基于图像合成的ISAR欺骗干扰研究

要实现对ISAR的欺骗干扰，设计一个好的假目标信号尤为重要，其关键在于如何产生一个好的相位调制系数对截获对方ISAR信号进行调制。文中提出了一种新的相位调制系数，与已有的相位调制系数相比，它不仅理论表达式简洁更易工程实现，而且考虑了假目标调相位置因子，设计出的假目标信号携带信息更丰富、灵活性更大。理论分析和仿真结果证明了所提出相位调制系数是有效的。     

利用窄脉冲技术的天线测量系统

介绍一种利用窄脉冲技术对天线电性能进行测试的设备。该设备不需要传统测试中的信号源发射连续波信号,其发射和接收的均是窄脉冲信号,然后将接收到的窄脉冲信号进行快速傅里叶变换计算出各频率上的幅度相位信息,因而在天线方向图测量时快速高效,而且可以利用时窗技术选取测试主信号,消除多路反射,杂波干扰等信号,故不需要微波暗室也能实现对天线的精确测量。