Angle of Arrival Statistics for a 3-D Cylinder Model

In this paper, a three-dimensional (3-D) geometric model is considered to simultaneously describe angle of arrival (AoA) of multipath waves in the azimuth and elevation planes. The model is suitable in a macrocellular environment with a low MS antenna and an elevated base station (BS), where scatterers are distributed in a cylinder with the radius of the cell and the height of the BS. Closed-form expressions for the probability density functions in the angles are provided as seen from the mobile station (MS). Results show that the azimuth AoA depends on the ratio of the distance between the BS and the MS to the radius of the cell whereas the elevation AoA depends on the height of the BS, the radius of the cell and the distance between the BS and the MS. Monte-Carlo simulations are performed to examine the accuracy of the proposed model.     

三维空间统计信道的空时参数AOA和TOA分析

针对在均匀散射体分布以及空间对称的3-D室内移动通信环境,细化了对于基站（BS,Base Station）以及移动台（MS,Mobile Station）端空间角度的研究。对在指向性天线覆盖下的室内微小区移动通信环境下,模型能估计多径衰落信道的重要空时信道参数,如波达信号在水平面以及竖直平面上的信号到达角度（AOA,Angle of Arrival）以及到达时间（TOA,Time of Arrival）。数值仿真结果与2一D多径衰落信道对比表明本模型的信道参数估计结果符合理论和经验,扩展了3一D空间统计信道模型的研究和应用。     

三维MIMO信道物理模型的统计特征

提出以散射矩阵来概括并简化电波传播过程中散射体对电磁波的影响,并对传统的距离分集和极化分集多入多出（MIMO）信道模型进行扩展,建立了一种可以应用于各种分集情况的三维通用MIMO物理信道模型。再以此模型为基础,对三维环境中的MIMO信道统计特征进行了研究,推导出任意情况下交叉极化鉴别度（XPD）和子信道间相关性的计算方法,并进行了仿真验证。仿真结果表明从文中所提出信道模型提取得到的统计特征与理论分析的结果是相符的。     

A Simple 3-D Geometric Channel Model for Macrocell Mobile Communications

One of the fundamental research areas in wireless communications is the development of realistic models that can efficiently and accurately describe the wireless propagation channel. Most of the proposed models disregard the three dimensional character of the signal spread or use techniques with excessive computational complexity. In this paper, we develop a simple 3-D geometric scattering model for the uplink of a macrocell mobile environment that provides the statistics of Angle-of-Arrival (AoA) of the multipath components. The model extends the 2-D geometrical-based single bounce macrocell (GBSBM) model. Explicit closed-form expressions are derived for the statistics of the AoA of the multipaths in the azimuth and elevation planes. Analysis of the results exhibits the advantages of our proposal compared to 2-D and 3-D ones published in the literature. Comparisons with experimental data confirm its validity. Interesting conclusions for the effective evaluation of mobile communication systems have been derived. Moreover, an application of the model to mobile location estimation has been developed and evaluated.     

双通道角跟踪体制实时校相算法研究

双通道单脉冲角跟踪体制在航天测控设备中应用广泛。通过深入研究国内双通道单脉冲角跟踪体制数字接收机角误差解调原理,提出一种高效率、高精度的实时校相的算法模型,旨在缩短设备任务准备时间,提高设备使用效率,提高设备应急测控能力,同时也为国内测控领域后续设备研制与生产提供相关技术参考。     

基于高阶统计的空间信号频率与二维到达方向估计

基于一个线性阵列、两个孤立阵元以及输出信号四阶累积量,本文提出了一种多个空间窄带信号频率、到达方位角和仰角估计方法.方法不仅使它们的估计无需谱峰搜索且自动配对,而且使阵列的阵元数大大减小,适合任意高斯噪声环境.计算机模拟结果证实了方法的可行性.     

A Hybrid SIM-SEM Method for 3-D Electromagnetic Scattering Problems

A new method combining the spectral integral method and spectral element method (SIM-SEM) is proposed to simulate 3-D electromagnetic scattering from inhomogeneous objects. In this hybrid technique (a special case of the finite element boundary integral (FEM-BI) combination), the SEM with the mixed-order curl conforming vector Gauss-Lobatto-Legendre (GLL) basis functions are used to represent the interior electric field with high accuracy, while the SIM on a cuboid surface is used as an exact radiation boundary condition. The Toeplitz property of the SIM matrix is utilized to reduce the memory and CPU time costs in an iterative solver by using the fast Fourier transform algorithm. Unlike the traditional FEM-BI combination where the BI portion usually dominates the computational complexity, the computational costs are much lower in the SIM-SEM method. Numerical results verify the accuracy and capability of this method, confirming that the SIM-SEM method is a good alternative for solving scattering problems from inhomogeneous objects.      

短沟道双栅MOSFET二维表面势解析模型

采用分解电势的方法求解二维泊松方程,建立了考虑电子准费米势的短沟道双栅MOSFET的二维表面势模型,并在其基础上导出了阈值电压、短沟道致阈值电压下降效应和漏极感应势垒降低效应的解析模型。研究了不同沟道长度、栅压和漏压情况下的沟道表面势,分析了沟道长度和硅膜厚度对短沟道效应的影响。研究结果表明,电子准费米势对开启后的器件漏端附近表面势有显著影响,新模型可弥补现有模型中漏端附近表面势误差较大的缺点;对于短沟道双栅MOSFET,适当减小硅膜厚度可抑制短沟道效应。     

圆筒散射的无人机MIMO信道模型研究

针对无人机环境特点和多天线系统,建立了基于圆筒散射的三维几何无人机MIMO宽带信道模型。该模型不仅由直射、反射和散射等多种分量组成,还考虑了飞行参数、散射环境以及天线间距等因素。根据地面控制站方位角非全向散射和俯仰角非对称分布的特点,结合无人机实际飞行参数特点,推导出简洁的闭环空时频联合相关函数,并通过仿真进行了有效性和可行性验证。     

Delay Analysis for a TDMA Channel with Contiguous Output and Poisson Message Arrival

An analysis of the exact delay of a TDMA or a loop communication system with a contiguous output and a Poisson message arrival process is presented. The nonlinear relationship of a contiguous output with arbitrary arrival process can be expressed by an infinite series. In the case of a Poisson message arrival process, the series can be summed to a closed form. The derived result, which is validated by simulation, is a vast improvement over the previously used approximate model of multiple frames with single output.     

基于隧道多散射信道的车载通信系统建模

为建立更高效的智能车对车(Vehicle To Vehicle,V2V)通信系统,针对密集隧道空间多入多出系统(Multiple Input Multiple Output,MIMO)移动传播环境,提出新型三维(Three Dimensional,3D)车载多散射通信信道模型.分析波达信号水平面和仰角平面发射角(Ang...     

Model Specification of a Noncausal 3-D AR Process Using a Causal 3-D AR Model on the Nonsymmetric Half-Space

There exists a causal 3-D AR process on the nonsymmetric half-space having the same autocorrelations as a noncausal 3-D AR process. A formula is presented to relate the AR coefficients of the noncausal 3-D AR process with those of the causal 3-D AR process on the nonsymmetric half-space. The 3-D Yule-Walker equations are derived for causal 3-D AR models on the nonsymmetric half-space, and a computationally efficient order-recursive algorithm is proposed to solve the 3-D Yule-Walker equations. We can easily specify a noncausal 3-D AR process from its autocorrelations using the autocorrelation equivalence relation, the formula of the AR coefficients and the order-recursive algorithm.     

Characterization of Arrival Statistics of Multiplexed Voice Packets

An assumption that voice packets arrive by a Poisson arrival (or an exponential interarrival) distribution has not widely been accepted by analysts from an obvious observation that voice packets are generated at regular intervals in a talkspurt. Through a simulation, supported by an approximate analysis, this paper claims that when a sufficiently large number of voice sources are multiplexed, packets observe an exponential or hypoexponential interarrival distribution. When the number of packets arriving during a single or a multiple slot is considered instead, a more liberal claim is made that regardless of the number of voice sources multiplexed, a Poisson process can be assumed with reasonable accuracy.     

Passive Source Localization Using Time Differences of Arrival and Gain Ratios of Arrival

A source signal will be subject to different amounts of time-delay as well as attenuation when it reaches a number of spatially separated sensors. Both time-delay and attenuation are dependent on the distance between the source and the receivers. This paper performs a fundamental investigation of whether the gain ratios of arrival (GROAs), defined here as the ratio of the received signal amplitudes at the referenced sensor to the other sensors, can be utilized in conjunction with the time differences of arrival (TDOAs) to improve the source localization accuracy. We begin with a Gaussian random signal model and derive the Cramer-Rao lower bound (CRLB) of a source location estimate based on both GROAs and TDOAs. Our conclusion is that the improvement from GROAs increases when the factor c/omega_o increases, where c is the signal propagation speed and omega_o is the signal bandwidth. The paper proceeds to develop an algebraic closed-form solution for the source location using GROAs and TDOAs. The algebraic solution is proved theoretically to reach the CRLB accuracy under the Gaussian data model. Numerical simulations are included to support and corroborate the theoretical developments.     

短沟道MOSFET渡越时间物理模型

叙述了一个考虑包括速度过冲等短沟道效应的ＭＯＳＦＥＴ渡越时间解析模型，计算结果与二维数值模拟符合较好。基于该模型，探讨了在线性工作区和饱和工作区渡越时间对栅偏压依赖关系的不同，并作了物理解释。模型还表明由速度过冲带来渡越时间的缩短对沟道长度大于０．２５μｍ的ＭＯＳＦＥＴ不超过１０％     

Statistics of 2-D DT-CWT Coefficients for a Gaussian Distributed Signal

This paper deals with the statistical properties of the two-dimensional dual-tree complex wavelet transform (DT-CWT) coefficients of a Gaussian distributed signal both in the Cartesian and polar forms. The first level of decomposition of the DT-CWT uses the wavelet filters that form only an approximate Hilbert-pair, while those at the higher levels form almost an exact Hilbert-pair. Hence, a significant correlation exists between the quadrature-filtered coefficients of the two trees in the first level of decomposition as compared to the other levels. As a consequence, in the Cartesian representation, the real and imaginary components of the complex coefficients are modeled as independent zero-mean Gaussian having unequal variances for the first level of decomposition and equal variances for the higher levels. In the polar representation, the magnitude components are modeled by a generalized Gamma probability density function (PDF) for the first-level decomposition and a Rayleigh PDF for the higher levels. The corresponding phase components are modeled by an analytic PDF. The Monte Carlo simulations show that the proposed PDFs of the transform coefficients match very well with the empirical ones. It is shown that the moments of the corresponding PDFs closely approximate the estimated sample moments. Finally, two techniques, namely, maximum a posteriori-based estimation and phase-based ridge detection are developed using the proposed PDFs. Simulation studies are carried out showing that the use of the proposed techniques provides improved estimation and detection performance of images in a noisy environment.      

基于聚类分析和神经网络的雷达目标三维散射中心提取

本文根据目标散射中心在雷达视线上的几何投影关系,分析了由多姿态角下一维散射中心重构雷达目标三维散射中心的基本原理和散射中心关联等技术难点,提出了基于聚类分析和神经网络两种三维散射中心提取方法并比较了二者特点。最后,本文采用GTD散射模型生成的回波数据和暗室测量数据进行实验,验证了两种方法具有实现简单、结果稳定等优点。     

到达时间差测量处理技术

短基线时差法测向体制原理简单,但需要现代化的时间间隔测量技术。本文给出一种到达时间差(DTOA)的测量处理方法,并给出实验结果。