CFAR处理中检测门限系数的研究

雷达系统在进行恒虚警处理时,通常采用的参考单元数是有限的。此时若采用理论的检测门限,将使虚警率大大增加。本文中我们通过仿真的方法确定CFAR中的实际门限系数,研究有限的参考单元数对虚警性能的影响。给出邻近单元平均恒虚警,选大恒虚警,选小恒虚警与加权单元平均恒虚警等四种检测器在不同参考单元数下的门限系数值。同时得出了不同恒虚警率下的门限系数。     

基于ADSP-TS201的着陆雷达恒虚警电路实现

恒虚警在着陆雷达系统中有着重要的作用和地位。恒虚警处理可以避免杂波变化影响检测阈值,提高雷达在各种干扰情况下的检测能力。文章首先介绍了恒虚警检测的原理,然后对几种典型方法进行了比较,选定单元平均选大恒虚警检测方法进行设计,并且实现了基于ADSP-TS201的恒虚警处理,最后通过Visual DSP++进行了仿真验证。     

脉冲多普勒雷达信号处理机中CFAR检测的仿真研究

CFAR检测器是雷达信号处理机中的重要组成部分。本文对脉冲多普勒雷达信号处理机中的CFAR检测器进行了仿真研究。给出了信号处理机中CFAR检测器的设计方案,对邻近单元平均恒虚警处理中的虚警概率、发现概率和恒虚警处理损失等问题进行了研究。分析了有限的参考单元数对虚警性能的影响,并给出了修正的门限系数。得出了不同参考单元数下的恒虚警损失,及恒虚警损失与相对门限系数之间的关系。得到了一定发现概率下所要求的信号处理机的输入信噪比。研究了信号处理机中其它部分对恒虚警处理性能的影响,如脉冲压缩对虚警率的影响等。     

基于GIS信息的CFAR检测器

在雷达信号检测过程中,为了实现恒虚警处理,必须采用动态门限。恒虚警检测器的门限设置通常是利用待检测单元附近的距离单元杂波数据进行计算得到的。然而,杂波环境的非均匀性导致了杂波功率随着距离变化剧烈,常规的恒虚警检测器性能会显著下降。文中给出了基于地理信息系统的恒虚警检测算法,利用对杂波环境的了解程度,可以显著提高CFAR检测器的性能。利用IPIX雷达实测数据,验证了该算法性能优于常规的其他CFAR处理器。     

海杂波背景下的双参数单元平均恒虚警检测器

介绍了海杂波的幅度分布模型,指出了对于同一门限系数"尖锐"海杂波背景下的虚警率要明显高于噪声背景下的虚警率,提出了双参数单元平均恒虚警(CA-CFAR)检测器的结构框图,仿真分析了其检测性能.最后分别利用双参数CA-CFAR检测器和常规CA-CFAR检测方法对实测数据进行处理和比较,指出在虚警率一定的前提下前者相对于后两者在空间上可以自适应地改变门限系数以有效地抑制海杂波引起的高虚警.     

基于慢门限与快门限的雷达回波恒虚警处理算法研究

本文研究了慢门限恒虚警处理和快门限恒虚警处理算法,针对慢门限恒虚警电路模型使用对数减法来代替除法运算以提高效率;针对快门限恒虚警处理电路模型存在的边缘效应问题,采用双侧单元平均选大的解决方案,使雷达检测系统始终处于恒虚警状态。     

恒虚警处理在连发火炮多目标检测中的应用

针对连发火炮的复杂多目标环境,传统的单元平均恒虚警处理方法不能满足信号检测的要求。为了充分利用目标的运动信息,通过距离-多普勒二维恒虚警方法估计背景噪声,采用修正的单元平均恒虚警处理剔除目标之间的相互干扰,并结合双门限检测对连发火炮多目标回波进一步处理,引入动态阈值增强检测的鲁棒性。工程实践表明,该方法提高了回波信号的信噪比和信杂比,有效地实现了连发火炮多目标的检测,为下一步目标参数提取提供基础。     

雷达恒虚警性能分析

用蒙特卡罗方法，结合某炮位侦察雷达的恒虚警检测器，对雷达的恒虚警检测性能进行了定量分析，给出了线性接收机和对数接收机在不同恒虚警处理时的门限因子及相应的虚警概率，并分析了对数起点变化对虚警率的影响。     

基于自动删除算法的最大选择恒虚警检测器

基于自动删除单元平均(ACCA)恒虚警算法,提出一种新的恒虚警检测器(ACCAGO-CFAR)以提高CFAR检测的性能。它的前沿和后沿滑窗均采用ACCA算法来产生2个局部估计,取其中最大值作为总的背景功率水平估计,从而设置自适应检测门限。在SwerlingⅡ型目标假设下,推导出ACCAGO-CFAR在均匀背景下虚警概率P_(fa)的解析表达式。通过与其他现有方案进行比较,结果表明ACCAGO在均匀背景及多目标和杂波边缘引起的非均匀背景中,均具有较好的检测性能,尤其是在杂波边缘环境中,它的虚警尖峰比ACCA小近2个数量级,并且处理时间也比ACCA大为缩短。     

基于恒虚警率的门限判决系数寻优研究

在雷达信号检测系统中,对于一定的检测门限,如果噪声或杂波电平增大一点,虚警率便会大大增加,同时使发现概率降低,这样便降低了雷达系统发现目标的能力,因此在现代雷达信号检测系统中,为了保证一定的发现概率,一般采取恒虚警率(CFAR)处理,在雷达系统进行恒虚警处理时,由于杂波强度可能偏离统计平均值而产生起伏,此时采用理论的门限判决系数将使虚警率大大增加。通过对雷达信号检测恒虚警性能的研究,分析了有限参考单元数对虚警率及发现概率的影响,同时提出一种有效的寻优算法在恒虚警检测中对实际的门限判决系数进行实时的动态寻优,使检测系统始终保持在恒虚警的工作状态中。     

一种改善导航雷达恒虚警检测效果的算法

传统的恒虚警检测器在进行目标检测时,容易受到其他目标和强海杂波的干扰,造成自遮蔽效应,使得大目标和大块地物（陆地、岛屿）回波出现“挖空”现象.通过自适应调整参考单元与保护单元的设置以适应不同的检测环境,在理论上可以有效克服“挖空”现象,但是这种自适应技术在实际雷达中很难应用.针对这种“挖空”现象,以某型导航雷达为例,利用陆地（或岛屿）杂波和大目标在幅度上与海杂波回波的差异对一定范围内的数据进行修复,最后基于导航雷达的实测数据对文中算法进行验证,结果表明,该算法明显改善了导航雷达的回波显示质量,有利于目标的凝聚与跟踪,且运算量适中,便于工程实现.     

AC PDP介质保护膜材料的选择

随着对交流等离子体显示板电压变化原因的探讨，新型表面保护材料的开发研究以及为除去污染而对制造工艺的调整，ＡＣＰＤＰ正在获得极好寿命特性。介质保护膜直接与放电气体相接触，其材料和表面状况是决定ＡＣＰＤＰ寿命及放电性的重要因素，因而保护膜材料的选择尤为重要。     

AC PDP介质保护膜的制备方法

本文分析了ＡＣＰＤＰ保护膜对制备方法的特殊要求，描述了各种制备方法的优缺点，介绍了几种最近发展起来的新方法。提出了几种适用于ＡＣＰＤＰ保护膜制备的方法。     

热处理工艺对AC PDP中MgO保护膜性能的影响

保护膜的表面特性严重影响ＡＣ ＰＤＰ的性能,本文以电子束蒸发法制得的ＭｇＯ保护膜为例,有关热处理条件对保护膜表面基本特性,如结晶结构,表面形貌及成分等的影响进行了研究。     

高功率横流CO2激光器集散控制系统的研究

本文研究了一种用于高功率横流CO2激光器的集散控制系统。该系统兼具监测、控制、报警、保护四大功能。同时该系统在对激光器最重要的参量输出激光功率的检测研究方面，有其重要进展，该系统研制了一种新型的围内尚未解决的尾镜取样功率檎测法，该检测方法线性度好，可实现对激光功牢的实时检测叉不影响激光输出。     

光束线真空联锁保护系统性能评估测试

光束线真空联锁保护系统的主要功能是在束线薄窗破裂或实验站发生灾难性事故时,防止大气直接冲入储存环真空系统,并尽量减少漏入环真空室的气体量。光束线真空联锁保护系统主要由快阀、门阀、压力传感器(真空规)和控制系统等组成。本实验室一期时研制的第一套真空联锁保护系统进行了模拟性的性能测试。性能测试所得到的数据为光束线真空联锁保护系统的实际应用提供了可靠数据。     

A new adaptive MAC layer protocol for broadband packet wirelessnetworks in harsh fading and interference environments

A new medium-access protocol is proposed for sharing a high-speed radio channel among a number of small wireless packet-access units, some of which may be stationary and some of which may be within moving vehicles. Such a system could provide fixed-point pedestrian and remote users with wireless access to CPU and database resources of an underlying asynchronous transfer mode (ATM) wireline network, essentially extending the ATM bandwidth-upon-demand interface directly to the wireless units and enabling delivery of multimedia services (albeit at the lower peak rate afforded by the radio channel). A primary goal of the proposed medium-access protocol is the pre-delivery of a signal from each packet-access unit as needed to rapidly compute the weights needed by a base station's adaptive array processor or a space-time processor, thereby protecting the packet flow in each direction from the effects of both multipath propagation and adjacent channel interference arising in neighboring radio cells. An impairment-robust direct sequence spread-spectrum-based polling signal is invoked to stimulate a pilot tone from a given remote immediately prior to packet transfer in either direction, thereby permitting the base station to determine a good set of antenna element combining or power splitting weights to be used for that packet. Reasonable approximations are invoked to study the performance of the proposed protocol and the link utilization efficiency and average message delay are found. By proper choice of protocol parameters, a radio resource utilization efficiency of about 95% is readily achieved. The accuracy of the approximations is confirmed by extensive computer simulations     

Optimal power allocation for multi-user OFDM and distributed antenna cognitive radio with RoF

In cognitive radio (CR), power allocation plays an important role in protecting primary user from disturbance of secondary user. Some existing studies about power allocation in CR utilize 'interference temperature' to achieve this protection, which might not be suitable for the OFDM-based CR. Thus in this paper, power allocation problem in multi-user orthogonal frequency division multiplexing (OFDM) and distributed antenna cognitive radio with radio over fiber (RoF) is firstly modeled as an optimization problem, where the limitation on secondary user is not 'interference temperature', but that total throughput of primary user in all the resource units (RUs) must be beyond the given threshold. Moreover, based on the theorem about maximizing the total throughput of secondary user, equal power allocation algorithm is introduced. Furthermore, as the optimization problem for power allocation is not convex, it is transformed to be a convex one with geometric programming, where the solution can be obtained using duality and Karush-Kuhn-Tucker (KKT) conditions to form the optimal power allocation algorithm. Finally, extensive simulation results illustrate the significant performance improvement of the optimal algorithm compared to the existing algorithm and equal power allocation algorithm.     

A protecting layer for the dielectric in AC plasma panels

One of the important problems in the development of ac plasma panels is to produce panels that maintain stable characteristics for a long time. A new idea for using a protecting layer over the dielectric layer which isolates the electrodes from the gas was examined and good results were obtained. Moreover, besides stability, a considerable improvement of operating characteristics was achieved, including low-voltage operation capability. Sputtering of the protecting layer, which is thought to govern the life of plasma panels, occurs even to heat-resisting oxides of large binding energy, but the sputtering rate appears to be so slow that it hardly affects the panel life. Also, the rate of decomposition accompanying sputtering is small. The problem of cracks in the protecting layer, which is the cause of defective life characteristics in such respects as migration of the lead component of the dielectric layer onto the protecting layer and the direct exposure of the dielectric-layer glass to the discharge, was solved by process-technique improvements. This paper describes the merit of using a protecting layer, required performance for this layer, and experimental results, and discusses voltage stability and the results of selection of materials for it.     

Reliability modeling algorithms for a class of large repairable systems

The reliability performance of some multistate large repairable systems cannot be described by a dichotomy of success and failure but by probability and frequency distribution of several levels of performance, algorithms for reliability modeling of such systems consisting of several units, each contributing a finite amount to the total system capacity. The first algorithm describes system model building by the sequential addition of units and the second one can be used for taking off particular units from the system model. The algorithms are fast and can be easily implemented in a computer program.