基于APD面阵探测器的非扫描激光主动成像雷达

为了获得目标区域的高精度3-D距离图像,采用自研带读出电路的雪崩光电二极管（APD）面阵探测器组件,研制了一台非扫描激光主动成像雷达。雷达采用波长1.064μm脉冲激光泛光照射目标区域,APD面阵探测器组件接收目标漫反射激光回波信号,经信息处理获得目标区域3-D距离图像,对典型目标开展了3-D成像实验研究。结果表明,所研制的非扫描激光主动成像雷达可获得较好的目标区域3-D距离图像,成像距离达1.2km,距离分辨率为0.45m,成像帧频为20Hz。基于APD面阵探测器组件的非扫描激光主动成像雷达技术取得突破。     

Two-dimensional DOA estimation of coherent signals using acoustic vector sensor array

In this paper, we present two new methods for estimating two-dimensional (2-D) direction-of-arrival (DOA) of narrowband coherent (or highly correlated) signals using an L-shaped array of acoustic vector sensors. We decorrelate the coherency of the signals and reconstruct the signal subspace using cross-correlation matrix, and then the ESPRIT and propagator methods are applied to estimate the azimuth and elevation angles. The ESPRIT technique is based on the shift invariance property of array geometry and the propagator method is based on partitioning of the cross-correlation matrix. The propagator method is computationally efficient and requires only linear operations. Moreover, it does not require any eigendecomposition or singular-value decomposition as for the ESPRIT method. These two techniques are direct methods which do not require any 2-D iterative search for estimating the azimuth and the elevation angles. Simulation results are presented to demonstrate the performance of the proposed methods.     

基于二维网孔互连网络的并行矩阵乘算法

矩阵乘法是数值分析领域中一种十分常用的基本运算，被广泛应用于模式识别、图像和信号处理。由于矩阵运算具有局部性、一致性的特点，特别适合用二维网孔并行计算机来实现。文章讨论了基于二维网孔互连网络的矩阵乘并行算法的实现，首先给出了一种正方网孔处理机阵列的并行算法，然后将其推广到长方网孔处理机阵列中。最后通过在LSMPP计算机的应用，证明算法是可行的、有效的。     

G-APD阵列——一种具有单光子灵敏度的三维成像探测器

介绍了一种利用盖革模式雪崩二极管(G-APD)作为成像单元的新型阵列光电探测器,重点介绍了该新型成像光电探测器的关键技术、器件研发和系统应用的发展状况。G-APD阵列探测器兼具单光子探测灵敏度和皮秒级时间分辨率两大特点,适用于对极微弱光目标的三维成像探测。同时,G-APD阵列探测器又是一种全固态的光电探测器件,不仅体积小、重量轻、可靠性高,而且还可用现有的微光电子工艺进行规模化生产。因此,G-APD阵列是目前阵列光电探测器件的一个重大发展,必将在各种高端光电成像领域获得广泛的应用。     

Two-dimensional equirotational stack subspace fitting with anapplication to uniform rectangular arrays and ESPRIT

A two-dimensional (2-D) multiple invariance technique for computing signal subspaces for uniform rectangular arrays (URAs) of size M×N sensors is introduced. The method is based on a multiple maximum overlap configuration of the sensors in the array with m×n subarrays of (M-m+1)×(N-n+1) sensors each. We exploit the fact that the stacked subspace of the subarray sensor output signals admits a two-level equirotational stack parametrization. We introduce a TLS-type algorithm for estimating the parameters of this equirotational stack subspace model. Based on this method of equirotational stack subspace fitting, the overall array signal subspace can be estimated with a much higher accuracy than with conventional unstructured SVD and TLS techniques. Detailed experiments validate the theoretical results. We propose a variant of 2-D ESPRIT based on equirotational stack subspace fitting. This 2-D equirotational stack ESPRIT (2-D ES-ESPRIT) algorithm clearly outperforms conventional unstructured variants of 2-D ESPRIT. A detailed comparison with 2-D unitary ESPRIT is presented     

采用降秩多级维纳滤波器的二维DOA估计快速算法

针对双平行线阵的二维波达方向(DOA)估计问题,为有效降低计算复杂度,提出了一种基于降秩多级维纳滤波器(MSWF)的快速算法。首先利用MSWF的前向递推实现信号子空间的快速估计,无需估计协方差矩阵和特征分解;然后,通过MUSIC算法对方位角和俯仰角的估计进行分维估计,使二维DOA估计退化为两个一维DOA估计问题,且方位角和俯仰角自动配对,进一步降低了运算量。仿真结果表明,该方法的估计精度优于同样基于双平行线阵提出的波达方向矩阵法(DOAM),俯仰角兼并时同样适用,计算复杂度低,适用于实时性要求高的应用背景。     

640×512制冷探测器积分时间与SNR分析

对国产640512中波凝视型制冷焦平面探测器的积分时间与信噪比( SNR)之间的关系进行了研究，以积分时间与探测器输出信号和噪声关系的原理为基础，分别对探测器正常工作时的输出信号情况以及输出噪声情况做了仔细的分析。文中分析了随着积分时间的增加，实际探测器输出信号和噪声信号各自的增长关系，并通过大量的数据和图表印证了这种关系的正确性，并最终得出了积分时间对探测器信噪比的影响程度，给出了最佳工作积分时间。     

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.     

Design and analysis of a 2-D eigenspace-based interferencecanceller

This paper deals with the problem of eigenspace-based interference cancellation using a two-dimensional (2-D) rectangular array. An efficient 2-D signal blocking technique is presented to remove the desired signal from the received array data. In conjunction with the 2-D signal blocking technique, a positive definite matrix is further constructed and used to compensate the effect of the signal blocking operation on the sensor noise received by a 2-D eigenspace-based interference canceller (EIC). Therefore, the interference subspace required for computing the optimal weight vector of the designed 2-D EIC can be obtained by simply using conventional eigenvalue decomposition methods instead of any complicated generalized eigenvalue decomposition methods. The performances of the designed 2-D EIC under finite samples and steering angle error are also evaluated. The developed theoretical results are confirmed by several simulation examples     

一种基于修正数据矩阵的广义波达方向矩阵方法

该文提出了一种基于平面阵的相干信号二维DOA估计算法,文中先将平面阵分为3个具有旋转不变性的子阵列,并分别构造了3个子阵列的数据矩阵,结合这3个数据矩阵,构造了两种修正数据矩阵,提高了阵元利用率。然后仿照波达方向矩阵的构造方法,得到了一种广义波达方向矩阵。通过理论分析证明了对该矩阵进行特征分解,就可以获得信号的方向矢量和信号方向元素,从而能够进行相干信号的二维DOA估计,并且避免了谱峰搜索,减少了运算量,仿真结果验证了该算法的有效性和精确性。     

ECG data compression using cut and align beats approach and 2-D transforms

A new electrocardiogram (ECG) data compression method is presented which employs a two dimensional (2-D) transform. This 2-D transform method utilizes the fact that ECG signals generally show two types of redundancies--between adjacent heartbeats and between adjacent samples. A heartbeat data sequence is cut and beat-aligned to form a 2-D data array. Any 2-D compression method can then be applied. Transform coding using the 2-D discrete cosine transform (DCT) [2-D DCT] is employed here as an example. Using selections from the MIT-BIH arrhythmia and Medtronic databases, results are presented that illustrate substantial improvement in compression ratio over one-dimensional methods for comparable percent root-mean-square difference (PRD).     

Reuse within a cell-interference rejection or multiuser detection?

We investigate the use of an antenna array at the receiver in frequency-division multiple-access/time-division multiple-access systems to let several users share one communication channel within a cell. A decision-feedback equalizer (DFE) which simultaneously detects all incoming signals is compared to a set of DFEs, each detecting one signal and rejecting the remaining as interference. We also introduce the existence of a zero-forcing solution to the equalization problem as an indicator of near-far resistance of different detector structures. Near-far resistance guarantees good performance if the noise level is low. Simulations show that with an increased number of users in the cell, the incremental performance degradation is small for the multiuser detector. We have also applied the proposed algorithms to experimental measurements from a DCS-1800 antenna array testbed. The results from these confirm that reuse within a cell is indeed possible using either an eight-element array antenna or a two-branch diversity sector antenna. Multiuser detection will, in general, provide better performance than interference rejection, especially when the power levels of the users differ substantially. The difference in performance is of crucial importance when the available training sequences are short     

Minimally Redundant 2-D Array Designs for 3-D Medical Ultrasound Imaging

In real-time ultrasonic 3-D imaging, in addition to difficulties in fabricating and interconnecting 2-D transducer arrays with hundreds of elements, there are also challenges in acquiring and processing data from a large number of ultrasound channels. The coarray (spatial convolution of the transmit and receive arrays) can be used to find efficient array designs that capture all of the spatial frequency content (a transmit–receive element combination corresponds to a spatial frequency) with a reduced number of active channels and firing events. Eliminating the redundancies in the transmit–receive element combinations and firing events reduces the overall system complexity and improves the frame rate. Here we explore four reduced redundancy 2-D array configurations for miniature 3-D ultrasonic imaging systems. Our approach is based on 1) coarray design with reduced redundancy using different subsets of linear arrays constituting the 2-D transducer array, and 2) 3-D scanning using fan-beams (narrow in one dimension and broad in the other dimension) generated by the transmit linear arrays. We form the overall array response through coherent summation of the individual responses of each transmit–receive array pairs. We present theoretical and simulated point spread functions of the array configurations along with quantitative comparison in terms of the front-end complexity and image quality.      

A method of ultrasonic 3-D computed velocimetry

A method of ultrasonic three-dimensional (3-D) vector velocimetry, which is derived by extending the previously proposed two-dimensional (2-D) vector velocimetry, is presented. In the proposed method, the three vector components of velocity to be measured are defined as the velocity in the beam axial direction, and angle velocities in two transverse directions. To derive the three components of velocity, signals detected by a 2-D array transducer are first 2-D Fourier transformed in the spatial domain parallel to the 2-D array transducer and then are one-dimensional (1-D) Fourier transformed in the time domain. The advantage of the proposed method is that it uses a linear signal processing, so it can simultaneously measure individual velocities of multiple scatterers. Computer simulations clearly demonstrate the effectiveness of the proposed method     

基于分数阶傅里叶变换的线性调频信号二维波达方向估计

 本文提出了一种基于分数阶傅里叶变换(Fractional Fourier Transform,FRFT)的多线性调频(Linear Frequency Modulation,LFM)信号二维波达方向(Direction of Arrival,DOA)估计方法.该方法利用FRFT对LFM信号的能量聚集特性,构造出一种新的分数阶傅里叶域的阵列信号数据模型,并利用MUSIC算法实现对多个LFM信号的二维DOA估计.仿真实验验证了算法的有效性.     

非中心化chi平方伽玛分布杂波模型

韦布尔和对数正态分布雷达杂波模型可描述海杂波的分布,但实现模型不同,且不能对杂波物理成因做出合理解释.这里提出一种非中心化chi平方伽玛分布模型,可精确地模拟海杂波,概率分布特性可与上述两者接近,并且能从物理含义说明杂波产生机理.模拟结果的概率密度分布和功率谱密度估计显示出这种模型具有很好的性能.     

二维相干信号波达方向判断空间平滑算法

波达方向估计是智能天线的重要功能之一,对于相干信号角度模糊问题通常严重影响了方向判断的精准度.文中根据一维空间平滑基本理论和算法,对二维六边形阵列相干信号MUSIC算法波达方向估计问题进行了理论分析和仿真实验,提出了平面六边形阵列到十字形阵列的变换方法,成功地把一维平滑技术应用到平面六边形阵列,仿真表明,这种变换可以有效地消除相干信号的角度模糊问题.     

Applications of detection and estimation theory to large array seismology

The statistical theory of signal detection and estimation has been applied to problems in large array seismology. Using this theory the structure of the optimum detector for a known signal and long observation time in additive Gaussian noise is derived. The array processing filter employed by the optimum detector is known as the maximum-likelihood filter. This filter also has the property that it provides a minimum-variance unbiased estimate for the input signal when it is not known, which is the same as the maximum-likelihood estimate of the signal if the noise is a multidimensional Gaussian process. A series of experiments was performed using data from the large aperture seismic array to determine the effectiveness of the maximum-likelihood method relative to simpler methods such as beam-forming. These results provide significant conclusions regarding the design and processing of data from large seismic arrays. The conventional and high-resolution estimation of the frequency-wavenumber spectrum of the background microseismic noise is also presented. The diffuse structure of this spectrum is shown to aid in explaining the relative performance of array processing methods.     

On the dynamics of two-dimensional array beam scanning viaperimeter detuning of coupled oscillator arrays

Arrays of voltage-controlled oscillators coupled to nearest neighbors have been proposed as a means of controlling the aperture phase of one-dimensional (1-D) and two-dimensional (2-D) array antennas. It has been demonstrated, both theoretically and experimentally, that one may achieve linear distributions of phase across a linear array aperture by tuning the end oscillators of the array away from the ensemble frequency of a mutually injection-locked array of oscillators. These linear distributions result in steering of the radiated beam. It is demonstrated theoretically that one may achieve similar beamsteering in two dimensions by appropriately tuning the perimeter oscillators of a 2-D array. The analysis is based on a continuum representation of the phase in which a continuous function satisfying a partial differential equation of diffusion type passes through the phase of each oscillator as its independent variables pass through integer values indexing the oscillators. Solutions of the partial differential equation for the phase function exhibit the dynamic behavior of the array during the beamsteering transient