Wideband angle of arrival estimation of chirp signals using virtual Wignerville distribution

To estimate the angle of arrivals （AOA） of wideband chirp sources, a new timo-frequency algorithm is proposed. In this method, virtual sensors are constructed based on the fact that the steering vectors of wideband chirp signals are linear and vary with time. And the randon Wignersville distribution （RWVD） of real sensors and virtual sensors are calculated to yield the new time-invariable steering vectors, furthermore, the noise and cross terms are suppressed. In addition, the multiple chirp signals are selected by their time-frequency points. The cost of computation is lower than the common AOA estimation methods of wideband sources due to nonrequirement of frequency focusing, interpolating and matrix decomposition, including subspace decomposition. Under the lower signal noise ratio （SNR） condition, the proposed method exhibits better precision than the method of frequency focusing （FF）. The proposed method can be further applied to nonuniform linear array （NLA） since it is not confined to the array geometry. Simulation results illustrate the efficacy of the proposed method.

Target Localization Based on Angle of Arrivals

Mobile location using angle of arrival （AOA） measurements has received considerable attention. This paper presents an approximation of maximum likelihood estimator （MLE） for localizing a source based on AOA measurements. By introducing an intermediate variable, the nonlinear equations relating AOA estimates can be transformed into a set of equations which are linear in the unknown parameters. It is an approximate realization of the MLE. Simulations show that the proposed algorithm outperforms the previous contribution.

Refractivity estimations from an angle-of-arrival spectrum

This paper addresses the probability of atmospheric refractivity estimation by using field measurements at an array of radio receivers in terms of angle-of-arrival spectrum. Angle-of-arrival spectrum information is simulated by the ray optics model and refractivity is expressed in the presence of an ideal tri-linear profile. The estimation of the refractivity is organized as an optimization problem and a genetic Mgorithm is used to search for the optimal solution from various trial refractivity profiles. Theoretical analysis demonstrates the feasibility of this method to retrieve the refractivity parameters. Simulation results indicate that this approach has a fair anti-noise ability and its accuracy performance is mainly dependent on the antenna aperture size and its positions.

Angle-of-arrival fluctuations in moderate to strong turbulence

Based on the modified spectrum, the analytic expressions for the variance and normalized covariance of angleof-arrival （AOA） fluctuations are presented, which are applicable to the weak and strong regimes. The experimental data of AOA fluctuations validate the new derived expressions in weak and strong regimes. The results show that the receiving aperture D, outer scale and cell scale larger than the scattering disc S contribute significantly to the AOA fluctuations, and contributions from the small-scale turbulence are negligible. For the case of 4S/D 〈〈 1, the receiving aperture dominates low-pass filtering effects and the new displacement variances are in good agreement with the results from the old weak-fluctuation theory. For the case of 4S/D 〉〉 1, the scattering disc dominates the low-pass filtering effects and the new displacement variances depart from the results from the old weak-fluctuation theory.

Performances Analysis of a System of Localization by Angle of Arrival UWB Radio

The increasingly widespread use of sensor and actuator networks and in general of the Internet of Things (IoT) in several areas of precision, imposes upon localization systems that can often equip them with a robust and more precise localization. It is in this sense that UWB technology has proved to be one of the most powerful communication technologies for these localization systems;thanks, in particular to the bandwidth occupied instantaneously by the signal allowing a very fine temporal resolution. Constructors have set up localization kits based on various technologies. These kits facilitate in a way the work of localization of users. In this paper, we present results on the performance study of the Decawave PDoA Kit. This Kit uses the PDoA (Phase Difference of Arrival) to determine the Angle of Arrival (AoA) parameter with UWB technology. This study is in context of localization by AoA for an application to protect agricultural crops against grain-eating birds. The results of the study show overall AoA measurement errors around 10 degrees in an ideal environment.

Beamforming and Angle-of-Arrival Estimation of Square Planar Antenna Array

This paper presents a dual-band planar antenna array for ISM band applications (2.4 GHz and 2.45 GHz). This antenna is proposed for indoor applications and enables adaptive beamforming and angle of arrival (AOA) estimation. An adaptive beamforming algorithm is applied for a planar antenna array, which is able to steer its main beam and nulls in azimuth and elevation planes over a wide frequency band. Planar antenna array operates as a spatial filter in 3D space, processing the received signals with weighting schemes. A planar antenna array is designed for AOA estimation in azimuth and elevation planes by using MUltiple SIgnal Classification (MUSIC) based on subspace algorithm. The Base Station (BS) equipped with this planar antenna is preferred to be at the center position on the room ceiling to cover all sectors of the room. It is designed to use four directional triangular elements arranged to form a square planar antenna array. Planar antenna with four elliptical slotted triangular elements (PAFESTE) is used to obtain optimal directivity in four directions in azimuth plane with specific orientation of 30? in elevation plane. It is characterized by half power beamwidth in elevation plane of about 60? and half power beamwidth in azimuth plane of about 90?.

Blind 2-D Angles of Arrival Estimation for Distributed Signals Using L-Shaped Arrays

Most existing two dimensional（2-D）angles of arrival（AOAs）estimation methods are based on the assumption that the signal sources are point sources.However,in mobile communications,local scattering in the vicinity of the mobile results in angular spreading as seen from a base station antenna array.In this paper,we consider the problem of estimating the 2-D AOAs of spatially distributed sources.First we perform blind estimation of the steering vectors by exploiting joint diagonalization,then the 2-D AOAs are obtained through two fast Fourier transforming of the estimated steering vectors.Simulations are carried out to illustrate the performance of the method.

Estimation of 2-D Angles of Arrival Based on Joint Diagonalization of Two Spatio-Temporal Correlation Matrices

In this paper, we propose a two-dimensional （2-D） angles of arrival （AOAs） estimation method based on a joint diagonalization of two spatio-temporal （ST） correlation matrices. The mathematical manipulations proposed in this paper take the structure of the array that enable estimating 2-D AOAs simultaneously without 2-D searching or pairing. The performance comparison shows that the proposed method is better than ST-DOA matrix method.

Accurate Angle-of-Arrival Measurement Using Particle Swarm Optimization

As one of the major methods for location positioning, angle-of-arrival (AOA) estimation is a significant technology in radar, sonar, radio astronomy, and mobile communications. AOA measurements can be exploited to locate mobile units, enhance communication efficiency and network capacity, and support location-aided routing, dynamic network management, and many location-based services. In this paper, we propose an algorithm for AOA estimation in colored noise fields and harsh application scenarios. By modeling the unknown noise covariance as a linear combination of known weighting matrices, a maximum likelihood (ML) criterion is established, and a particle swarm optimization (PSO) paradigm is designed to optimize the cost function. Simulation results demonstrate that the paired estimator PSO-ML significantly outperforms other popular techniques and produces superior AOA estimates.

LOCALIZATION ALGORITHM USING DISTANCE AND ANGLE INFORMATION IN WIRELESS SENSOR NETWORKS

A localization algorithm using distance and angle information is proposed in wireless sensor networks. Assuming that node axial orientations are unknown, all angles are measured to calculate the angle differences between two nodes viewed by the third one. Then, localization problems are formulated as convex optimization ones and all geometric relationships among different nodes in the communication range are transformed into linear or quadratic constraints. If all measurements are accurate, the localization problem can be formulated as linear programming （LP）. Otherwise, by incorporating auxiliary variables, it can be regarded as quadratic programming （QP）. Simulations show the effectiveness of the proposed algorithm.

On Time-of-Arrival Statistic of Gaussian Channel Model

A model of an angle-spread source, termed the “Gaussian Channel Model” is considered. The cumulative distribution function of the Time-of-Arrival of the multipath components is derived for an arbitrary angle spread. The simple approximate expressions for the Time-of-Arrival cumulative distribution function and probability density function are proposed. Numerical results obtained with the help of the derived expressions show the good coincidence with the experimental data and other known results.

无源雷达高速目标回波相参积累和参数估计算法

针对无源雷达高机动匀速目标参数估计中长时间积累引起的距离徙动效应问题,提出了一种基于Keystone变换和圆阵干涉仪测向的高效相参积累和参数估计算法。首先,根据目标运动和外辐射源信号参数,对参考信号和监视信号进行分段处理,段内为快时间,段间为慢时间;然后,利用Keystone变换对各频率的时间轴进行尺度变换,校正高速目标的距离徙动,继而将目标回波信号能量积累至同一时延-多普勒单元;最后,对目标回波所在的时延-多普勒单元进行圆阵干涉仪二维测向,得到目标方位角和俯仰角估计。仿真结果表明,算法可有效实现高机动匀速目标微弱回波信号的相参积累和参数估计,计算复杂度更低,对目标时延、多普勒、方位角和俯仰角参数估计的稳健性和精度更高。

基于非机动单站的目标运动状态无偏估计

为了解决远距离场景下基于非机动单站的目标跟踪问题,提出了一种基于三维到达角信息且具有渐进无偏特性的目标跟踪算法。以相对运动模型为研究对象,在速率先验已知的条件下,建立基于非机动单站的运动模型与观测模型,并对系统可观测性进行了分析。为了解决伪线性最小二乘算法的有偏性问题,提出了一种具有渐进无偏性能的约束总体最小二乘法,并证明了该方法的无偏性。仿真结果表明,在百公里级别的三维到达角跟踪中,角测量标准差分别为0.1°,0.2°,0.3°时,约束总体最小二乘法50~100 s内的时均相对距离误差能达到6%,12%,21%,时均绝对位置误差达到9,19,35 km;而初始距离为70,140,280 km时50~100 s内的时均相对距离误差能达到1%,6%,30%,时均绝对位置误差为0.7,9,30 km,100 s时的相对距离误差均能降到10%以内,精度提升效果最明显,且算法运行速度与伪线性最小二乘法在同一个量级。约束总体最小二乘法收敛速度快、定位精度高,且具有较快的运行效率,受测角误差与初始距离的影响较小,能够为远距离场景下的非机动单站三维到达角目标跟踪提供有效方法。

联合时延-多普勒-角度的无源雷达目标定位凸优化算法

针对分布式多输入多输出雷达中联合时延-多普勒-角度测量的运动目标定位问题,提出了一种基于半正定松弛的凸优化定位算法,改善了测量误差较大时定位误差偏离克拉美罗界的阈值效应.首先,将定位问题表述为最大似然估计问题,通过引入辅助变量将定位问题转化为带约束的加权最小二乘优化问题,然后使用半正定松弛技术,转化为半正定规划凸问题,并采用内点法对该凸问题求解得到目标位置和速度估计.由于凸优化问题的局部最优解就是全局最优解,本文算法具有良好的全局收敛性.仿真结果表明,与现有算法相比,本文算法的定位误差逼近克拉美罗下界,在大测量误差水平下的定位精度和稳健性优于现有算法.

基于漂移聚类的多目标抗干扰测向定位方法

随着有人/无人侦察机探测辐射源技术的快速提升与发展,多目标的无源测向定位一直是研究重点,本文提出了一种基于漂移聚类的多目标抗干扰测向定位算法。该算法基于二维空间进行设计,首先进行经纬度转换,再以聚类思想将测向线进行分组,排除聚类簇中测向数目较少的噪声测向线,最后将聚类迭代时求出的每组组内距离测向线最近的点作为定位点。实验结果表明,在含有噪声测向线的多目标无源测向数据中,该算法可较好地对多目标进行聚类并定位,定位准确率方面效果良好。

改进实值空时子空间数据融合的单星直接定位方法

辐射源直接定位是一种能够直接从原始采样信号中估计出辐射源位置的无源定位技术。利用单颗卫星对地球表面固定辐射源进行直接定位具有定位精度高、灵活性强等特点,因而具有重要的研究价值。然而,传统空域子空间数据融合直接定位方法缺乏对多普勒信息的充分利用,其在单星直接定位场景下的定位性能不足。现有空时子空间数据融合直接定位方法提升了该场景下的定位性能,但其仍存在低信噪比条件下定位精度和分辨率不足的问题。针对这些问题,该文提出了一种改进实值空时子空间数据融合的单星直接定位方法,实现了辐射源高程已知条件下单星对多辐射源的直接定位。首先,该文基于WGS-84地球椭球面模型建立联合到达角和多普勒频率的空时信号模型,充分利用了卫星相对辐射源高速运动产生的多普勒频移信息。随后,该文引入了托普利兹矩阵调整方法,对空时信号模型中接收信号的协方差矩阵进行分块,然后对分块矩阵进行调整,并使用前后向平滑和空时子空间酉变换技术来得到实值的空时子空间。最后,该文融合多个时隙的空时子空间数据建立定位的代价函数,同时设计出符合特征空间思想的分子函数,得到改进的代价函数,再通过网格搜索方法估计出辐射源的位置。仿真结果表明:所提方法在低信噪比下相比MUSIC(Multiple Signal Classification)直接定位方法、MVDR(Minimum Variance Distor tionless Response)直接定位方法、ML(Maximum Likelihood)直接定位方法和U-ST-SDF(Unitary Space-time Subspace Data Fusion)方法具有更好的定位性能。

Localization in modified polar representation: hybrid measurements and closed-form solution

Classical localization methods use Cartesian or Polar coordinates, which require a priori range information to determine whether to estimate position or to only find bearings. The modified polar representation (MPR) unifies near-field and farfield models, alleviating the thresholding effect. Current localization methods in MPR based on the angle of arrival (AOA) and time difference of arrival (TDOA) measurements resort to semidefinite relaxation (SDR) and Gauss-Newton iteration, which are computationally complex and face the possible diverge problem. This paper formulates a pseudo linear equation between the measurements and the unknown MPR position,which leads to a closed-form solution for the hybrid TDOA-AOA localization problem, namely hybrid constrained optimization(HCO). HCO attains Cramér-Rao bound (CRB)-level accuracy for mild Gaussian noise. Compared with the existing closed-form solutions for the hybrid TDOA-AOA case, HCO provides comparable performance to the hybrid generalized trust region subproblem (HGTRS) solution and is better than the hybrid successive unconstrained minimization (HSUM) solution in large noise region. Its computational complexity is lower than that of HGTRS. Simulations validate the performance of HCO achieves the CRB that the maximum likelihood estimator (MLE) attains if the noise is small, but the MLE deviates from CRB earlier.

深海垂直阵直达声区目标反卷积定位方法

深海声源定位的常规方法通常是利用水听器阵列接收声源信号的多途到达信息与仿真结果进行匹配实现定位。针对常规方法难以直接提取相近多途到达角的问题,提出了一种基于反卷积的深海垂直阵水下目标定位方法。该方法采用自适应迭代的频域Richardson-Lucy算法对深海声源目标多途到达角进行直接估计,通过匹配声场到达角特征模板实现测距与定深。仿真和实验结果表明,该定位方法比常规方法有着更高的定位精度与适用性,并且具有较高的计算效率。

Concurrent photonic measurement of angle-of-arrival and chirp rate of microwave LFM signal

A photonic approach to concurrently measure the angle-of-arrival(AOA) and the chirp rate of a linear frequency modulated(LFM) signal is proposed and experimentally demonstrated. The measurement is achieved by estimating the differential frequency of a two-tone signal output by a dual-parallel Mach–Zehnder modulator and an additional asymmetry Mach–Zehnder interferometer. Experiments show that the AOA and the chirp rate are measured simultaneously, with an AOA measurement error of ?0.1° at an signal-to-noise ratio(SNR) of 9.6 d B.When the SNR is-10.4 d B, the AOA error is ?1.3°, and the chirp rate, measured as 210.2 ? 1.5 Hz∕ps, has a standard deviation of 0.7%. The measured chirp rate agrees well with the real LFM signal.

基于复域超多维标度的混合TOA/AOA定位算法

针对全球卫星导航系统信号完全拒止环境下的定位问题,使用超宽带(UWB)技术获取测量信息,基于多维标度变换算法(MDS)提出一种复域下的混合测距信息(TOA)和测角信息(AOA)的超多维标度定位算法(TASMDS),并进一步构建了复域内的核矩阵,提出复域下的超多维标度定位算法(TA-CDSMDS)。对比3种算法的定位结果,以及10°、15°、20°测角误差和不同测距误差下的定位误差,得TA-CDSMDS算法相较于TA-SMDS和MDS,有更小的定位误差,更贴近克拉美罗下界;分析不同节点下3种的计算时间,TA-CDSMDS算法在优化TA-SMDS的基础上减少28%~48%的时间,具有更好的定位性能。