无源测向交叉定位的误差分析与校正

测向交叉定位在无源定位技术中应用广泛。在分析了多站交叉定位的系统误差与随机误差的基础上,将系统误差校正转换为非线性优化问题,并采用遗传算法寻优求解。将随机误差依据数据融合理论进行融合改进。仿真结果表明,误差配准与校正后的测向交叉定位精度有了较大的提高。     

质心定位中的加权坐标误差修正方法

针对IoT中需求高精度节点定位的问题,提出了一种加权坐标误差修正的质心定位算法。首先对距离无关质心定位算法进行分析,然后使用RSSI测量标记节点与待定位节点的距离,并结合信号衰减度对坐标加权,最后对节点坐标误差修正,进一步精确节点坐标。实验仿真结果表明,本文提出的加权坐标误差修正方法相对于传统定位算法,有更强的抗干扰能力和鲁棒性。     

On the Cramer-Rao lower bound for RSS-based positioning in wireless cellular networks

An accurate position of a mobile user's location is substantial in wireless cellular networks with respect to location based services (LBS) implementation. Among the available parameters used to estimate a desired location, low cost measurement of received signal strength (RSS) makes it suitable for outdoor and indoor positioning. Our aim here is to look at the performance of a theoretically optimal user's position estimator. We examine the Cramer-Rao lower bound (CRLB), which sets the lowest variance of any unbiased estimator. Due to the oversimplification with respect to reliance on detailed cognizance of environment, we deploy theoretical free-space and empirical COST-231-Hata, Stanford University Interim (SUI) and ECC-33 path loss models that are dominantly used in real scenarios aiming to form the system model equations. The findings show that the CRLB on estimation precision depends on the underlying path loss exponents (PLE) and the relative positions of the mobile and base stations. The calculated bounds provide a benchmark against which it is possible to evaluate different positioning algorithms, techniques and estimators relying on the specified path loss models.     

Near-field time-frequency localization method using sparse representation

This paper presents a novel near-field source localization method based on the time-frequency sparse model.Firstly,the method converts the time domain data of array output into time-frequency domain by time-frequency transform;then constructs sparse localization model by utilizing the specially selected time-frequency points,and finally the greedy algorithms are chosen to solve the sparse problem to localize the source.When the coherent sources exist,we propose an additional iterative selection procedure to improve the estimation performance.The proposed method is suitable for uncorrelated and coherent sources,moreover,the improved estimation accuracy and the robustness to low signal to noise ratio(SNR) are achieved.Simulations results verify the efficiency of the proposed algorithm.     

单脉冲雷达速度量折射误差高精度修正方法

单脉冲雷达是高精度外弹道测量系统中的一种主要测量设备之一,为了提高其测量精度,对所有测量参数都需要进行电波折射误差修正.针对目前单脉冲雷达测速参数折射误差修正精度较低的现状,在距离和角度折射误差修正基础上,提出了基于方向余弦的速度量折射误差高精度修正方法.首先根据经折射修正后的目标精确位置,利用二阶中心平滑微分方法求出目标的真实速度向量;然后再利用测站、地心的位置得到目标到雷达站、地心的方向余弦,进而求出目标与雷达站间电波射线在目标处切矢方向余弦;最后进行距离变化率的折射误差修正.实验证明,该方法比常用的直接微分方法的精度高出20％,且具有较好的实用性和有效性.     

A new cell loss recovery method using forward error correction in ATM networks

A new method using an FEC technique is proposed to enhance the ability of consecutive cell loss compensation due to buffer overflow in ATM networks. This article summarizes different applications of cell loss recovery, and presents the design of a new coding scheme and the coding/decoding algorithm. © 1998 John Wiley & Sons, Ltd.     

稳定分布噪声下基于粒子滤波的双站伪多普勒定位方法

传统的伪多普勒测向算法在高信噪比和高斯噪声环境下能较为精确地计算出到达方位角,但对于稳定分布噪声的顽健性较差。针对以上不足,提出了一种基于粒子滤波的双站伪多普勒定位方法。用粒子滤波对2个接收机的来波方位角进行联合估计,并通过非线性映射得到信源位置坐标估计,实现了方位角计算与双站定位的集成。仿真实验表明,当稳定分布参数α为1.4（中等脉冲程度）时,所提方法在低信噪比下的顽健性要显著优于传统方法,在高信噪比时估计精度与传统方法相当;当信噪比为10 dB时,所提方法在 的情况下定位精度远高于传统方法。     

一种动静PIR相结合的目标定位方法

针对目前热释电红外(PIR)传感器在静态人体 检测方面的局限性,提出了一种在动态下利用多PIR传感器、 动静相结合对人员目标进行检测、测向与定位的方法。研究中,感知节点上的静态PIR传感 器对人员目标进行 测距,动态PIR传感器以10°/s的速率对监控区域往复式扫描,变被动为“主动”。当人员 目标与PIR传感器的探测视线 相交时,通过帧差法得到目标的角度值,融合多个传感器的测量值进行交叉定位,实现了在 探测区域对整 个目标事件过程的有效数据采集。实验证明,本文方法能很好地对不同状态下的人员目标进 行检测定位,具有实用价值。     

A novel TOA estimation method with effective NLOS error reduction

It is well known that non-line-of-sight （NLOS） error has been the major factor impeding the enhancement of accuracy for time of arrival （TOA） estimation and wireless positioning. This article proposes a novel method of TOA estimation effectively reducing the NLOS error by 60%, comparing with the traditional timing and synchronization method. By constructing the orthogonal training sequences, this method converts the traditional TOA estimation to the detection of the first arrival path （FAP） in the NLOS multipath environment, and then estimates the TOA by the round-trip transmission （RTT） technology. Both theoretical analysis and numerical simulations prove that the method proposed in this article achieves better performance than the traditional methods.     

基于线性误差模型的干涉仪系统标校方法

干涉仪系统利用多个天线构成测向基线,通过测量目标相位信息完成入射角度估计,能实现瞬时高精度测向.针对系统误差影响测向性能这一问题,分析了系统误差来源(包括天线安装误差和系统固定相位误差),建立了干涉仪系统误差线性模型,利用线性最小二乘算法对干涉仪系统中的天线相位误差与基线安装误差进行估计.仿真分析验证了该方法的有效性.     

利用三星时频差的运动辐射源定位与测速方法

针对高轨三星无源定位系统对空中恒定高度运动目标探测的应用场景,提出了一种利用信号到达时差( TDOA)、到达频率差( FDOA)的无源定位与测速方法。详细描述了算法原理、算法处理步骤,利用STK( Satellite Tool Kit)软件结合计算机仿真,分析了时差测量误差、频差测量误差、高程估计误差对定位精度与测速精度的影响。该方法定位精度与测速精度较高,具有一定的工程应用价值。     

红外鱼眼成像系统非均匀性校正方法

分析了时域高通滤波校正算法中容易出现目标退化及“伪像”的问题,指出滤波方程的截止频率与信号频域分布的变化不匹配是产生问题的原因。结合红外鱼眼系统成像的特点,通过目标检测的方法分辨需要调整滤波截止频率的像元,对其采用不同的时域高通滤波方式,即改变滤波器的截止频率,有效地减少了目标退化和伪像的影响。采用主观和客观评价指标对试验的红外序列图像进行评价,结果表明改进的时域高通滤波校正方法效果明显。     

基于分类的运动矢量平滑和纠正方法

对于帧率上变换算法中运动矢量估计不准确的问题,文中提出了一种新的运动矢量处理算法,较好地纠正了错误的运动矢量。该算法根据前后向运动矢量的一致性程度,以及对应块的绝对差值和,对运动矢量进行了可靠性分类。针对分布在纹理相似区的错误运动矢量,利用时间和空间相关性联合纠正;对于物体边缘区域则分解为小块重搜索运动矢量,以避免边缘模糊现象。实验结果显示,算法可以较好地纠正运动矢量。     

一种非迭代的位姿估计方法

针对深度相机运动中的位姿估计问题,提出了一种无需迭代的估计方法。首先,在二维图像上应用图像特征点提取和描述方法,完成不同视点的初始匹配。其次,选择初始匹配度量距离最小的2个特征点作为种子点。以三维空间中欧式距离与坐标系的建立无关为准则,对初始匹配进行筛选。剔除误匹配点对,进而计算运动位姿参数。最后,采用nyuv2图像数据库进行实验,验证了本文算法的可行性和正确性。实验结果表明:与传统算法相比,该方法计算效率平均提高了8倍以上,特别适用于大型场景中的同步定位和地图构建SLAM(Simultaneous Localization and Mapping)问题。     

白天卫星激光测距望远镜指向误差修正方法研究

白天卫星激光测距时,由于望远镜机架受太阳辐照和温度变化等因素影响,指向误差时变性较大,影响了对白天卫星的精确跟踪指向。针对卫星过境天区,提出了一种通过白天恒星监视,实现望远镜局部指向误差快速修正的方法,消除环境温度变化效应,实现高精度望远镜指向。以中国科学院上海天文台60 cm口径卫星激光测距系统为平台,应用短波截止滤光技术,实现了对亮于3等恒星的白天监视;并在卫星过境天区选择到6到7颗恒星进行观测,建立望远镜局部指向误差修正模型,以满足白天激光观测需求。该方法对白天卫星测距特别是高轨卫星等具有一定应用价值,也可推广到其他需白天目标观测的望远镜系统。     

数据异常值检测及修正方法研究

针对雷达测量数据中存在的异常值,对数据中的时间参数根据其变化规律的等差性进行异常值检测。对雷达发射功率、角度、距离参数异常问题,基于邻近去最值均值滤波原理,采用滑窗方式进行检测并修正。实验结果表明,提出的检测方法能够有效检测并修正数据中的异常跳变点且不改变正常值。     

频域自适应时延估计及其在被动声定位中的应用研究

研究了频域自适应时延估计算法及其在被动声定位中的应用。提出了一种改进时延估计性能的方法，并用实测直升机噪声数据进行了动态仿真，验证了算法的有效性，此项研究有重要的工程应用价值。     

一种人脸姿势估计新方法

本文提出了一种人脸姿势估计方法,基于单幅人脸图像的五个特征点:左右外眼角,左右嘴角和鼻尖估计人脸姿势,论文首先给出人脸姿势表示——旋转角度((?),ψ,θ),然后介绍了姿势估计方法,最后的实验结果证明了本文算法的有效性。     

A power supply error correction method for single-ended digital audio class D amplifiers

In single-ended digital audio class D amplifiers (CDAs), the errors caused by power supply noise in the power stages degrade the output performance seriously. In this article, a novel power supply error correction method is proposed. This method introduces the power supply noise of the power stage into the digital signal processing block and builds a power supply error corrector between the interpolation filter and the uniform-sampling pulse width modulation (UPWM) lineariser to pre-correct the power supply error in the single-ended digital audio CDA. The theoretical analysis and implementation of the method are also presented. To verify the effectiveness of the method, a two-channel single-ended digital audio CDA with different power supply error correction methods is designed, simulated, implemented and tested. The simulation and test results obtained show that the method can greatly reduce the error caused by the power supply noise with low hardware cost, and that the CDA with the proposed method can achieve a total harmonic distortion + noise (THD + N) of 0.058% for a –3 dBFS, 1 kHz input when a 55 V linear unregulated direct current (DC) power supply (with the –51 dBFS, 100 Hz power supply noise) is used in the power stages.     

A method for automatic design error location and correction in combinational logic circuits

We present a new diagnostic algorithm, based on backward-propagation, for localising design errors in combinational logic circuits. Three hypotheses are considered, that cover all single gate replacement and insertion errors. Diagnosis-oriented test patterns are generated in order to rapidly reduce the suspected area where the error lies. The originality of our method is the use of patterns which do not detect the error, in addition to detecting patterns. A theorem shows that, in favourable cases, only two patterns suffice to get a correction. We have implemented the test generation and diagnosis algorithms. Results obtained on benchmarks show that the error is always found, after the application of a small number of test patterns, with an execution time proportional to the circuit size. This work is partially supported by EUREKA “JESSI-AC3” project and the ESPRIT Basic Research Action CHARME Working Group #6018.