Resolving manifold ambiguities in direction-of-arrival estimationfor nonuniform linear antenna arrays

This paper addresses the problem of ambiguities in direction of arrival (DOA) estimation for nonuniform (sparse) linear arrays. Usually, DOA estimation ambiguities are associated with linear dependence among the points on the antenna array manifold, that is, the steering vectors degenerate so that each may be expressed as a linear combination of the others. Most nonuniform array geometries, including the so-called “minimum redundancy” arrays, admit such manifold ambiguities. While the standard subspace algorithms such as MUSIC fail to provide unambiguous DOA estimates under these conditions, we demonstrate that this failure does not necessarily imply that consistent and asymptotically effective DOA estimates do not exist. We demonstrate that in most cases involving uncorrelated Gaussian sources, manifold ambiguity does not necessarily imply nonidentifiability; most importantly, we introduce algorithms designed to resolve manifold ambiguity. We also show that for situations where the number of sources exceeds the number of array sensors, a new class of locally nonidentifiable scenario exists     

ICA-based direction-of-arrival estimation of uncorrelated and coherent signals with uniform linear array

A novel approach for direction-of-arrival (DOA) estimation of uncorrelated and coherent signals with uniform linear array is proposed in this paper. First, the mixing matrix, which contains all azimuth information of signal sources, is estimated by independent component analysis. Afterward, several parameter equations are established upon the new mixing matrix. Finally, all DOAs of coherent and uncorrelated signals are estimated by solving these equations. Compared with traditional methods, the proposed method has higher angle resolution and estimation accuracy. Moreover, the signal number resolved by our approach can exceed the number of array elements. Simulation results have demonstrated the efficiency of the proposed method.     

Four independent beams from a single linear array

This paper describes an antenna technique which combines the dual-mode operation of a radiating square waveguide transmission line with the attachment of multiple ports to produce an antenna which can generate multiple, independent beams in space. The technique can be used to simultaneously transmit or receive signals through the beams with considerable isolation (>37 dB) between several of the ports. By this technique a single, traveling-wave-operated, linear array was designed to generate four unique beams in space. The beams consisted of two pairs of image beams which were produced by the use of an even coupling function design in the aperture. Measurements made of the array model atX-band showed good agreement with theory.     

Design of coherently radiating structures in a linear array geometry using genetic algorithms

The design problem of coherently radiating structures in a linear array geometry is dealt with. The key idea is to accept the unavoidable presence of the mutual coupling between antenna elements but force it to be coherent by including additional passive elements in between the active ones. This design of coherently radiating structures considers the optimization of the spacing between antenna elements by using the well-known method of genetic algorithms. Simulation results for coherently radiating structures with uniform and non-uniform separation are provided. A comparative analysis of the performance of different coherently radiating structures is achieved in order to set new design philosophies in antenna arrays.     

A compact single layer injection-locked linear scanning array

A compact, single layer, CPW-fed, patch scanning array architecture using injection locking at 9.83 GHz is presented. The patch antennas are printed on the front side of the substrate while the electronics are situated at the back side leading to a simple and compact design. The unit element for the array is a self oscillating active patch antenna with a GaAs FET centered behind the patch for tight packing. The feedback for the oscillator is provided through electromagnetic coupling using a twin-slot arrangement behind the patch. A low power control signal is injected through parasitic coupling at the CPW side of the circuit. Phase shifting of the elements is achieved by electronically adjusting the gate voltage of the GaAs FETs. A scan range of -12°- +9.5° is obtained for a four element prototype array     

Concurrent speakers localization using blind source separation and microphone array geometry

Multidimensional Systems and Signal Processing - Speaker localization has been an active topic of research due to its wide range of applications in multimedia and communication technologies. While...     

DOA estimation of wideband sources using a harmonic source modeland uniform linear array

We consider the problem of estimation of the DOAs of multiple wideband sources incident on a uniform linear array (ULA) in the presence of spatially and temporally white Gaussian noise (WGN). The approach presented builds up on the IQML algorithm suggested by Bresler and Macovski (1986) for the case of narrowband DOA estimation. It is shown that the concept of an ARMA model for the observed data vector for the narrowband case can be generalized to model an appropriately stacked, space-time data vector obtained by combining the space-time samples. The coefficients of the corresponding 2-D predictor polynomial can be used to represent the null subspace of the wideband array steering matrix, and rooting of the polynomial at each frequency, separately, gives the DOA estimates. These separate estimates at multiple frequencies are combined into a single DOA estimate in a least squares sense. This leads to the formulation of an IQML like procedure for the spatial parameter estimation of wideband sources. Like its narrowband counterpart, the proposed approach is applicable to both noncoherent and coherent sources. The performance of the proposed method is studied via extensive computer simulations and by comparison with the Cramer-Rao bounds     

高斯白噪声下L阵二维波达方向快速估计

针对L型阵列,提出一种在高斯白噪声环境下的二维波达方向( DOA)快速估计方法。首先利用阵列结构特点构建两个互协方差矩阵,同时实现了噪声分量的有效抑制,再依据协方差矩阵的性质构造了波达方向矩阵。对该矩阵进行一次特征分解即可分别得到包含方位角和俯仰角信息的方向矢量和方向元素,实现二维DOA估计。该算法避免了传统算法的谱峰搜索或大矩阵构造及其特征分解过程,计算量小,且参数自动配对。仿真结果表明,该算法在低性噪比和少快拍下的估计精度与2 D ESPRIT算法近似,但计算复杂度大幅降低,适用于实时性高的工程应用背景。     

单快拍虚拟阵列Toeplitz矩阵重构的相干信源DOA估计

针对相干信源的DOA估计,提出一种基于单快拍虚拟阵列Toeplitz矩阵(SSVT)重构的解相干算法。该方法利用阵元接收的单快拍数据构造出双向虚拟子阵,并对虚拟子阵的协方差矩阵的平均值进行Toeplitz矩阵重构,实现对相干信源的DOA估计。该方法无需进行多次快拍,在不损失阵列孔径和工作阵元的基础上实现相干信源的DOA估计。仿真结果表明,该算法降低了运算量,在低信噪比的情况下也能分辨M-1个相干信源。     

Adaptive control of a flexible linear array

A system has been constructed which adaptively corrects for an applied phase error along the length of a flexible linear array. The system utilises resistance strain gauges and electrically controlled ferrite phase shifters. Results at 9.4 GHz are presented, in the form of radiation patterns, to provide an illustration of the system performance.     

Numerical analysis of wave propagation on a periodic linear array

The propagating mode on a periodic array of wires or strips is studied. Numerical solutions of the current distribution on each element, the propagation constant, and the cutoff frequencies of the propagating mode are found. It is discovered that this periodic structure in some cases can support propagating waves in two or more widely separated frequency bands.     

Blind source extraction based on a linear predictor

A rigorous analysis of the blind source extraction (BSE) approach based on a linear predictor is provided. It is shown that by minimising the mean squared prediction error (MSPE), as originally proposed, it is only possible to reach a solution subject to an arbitrary orthogonal transformation. To remove this ambiguity, a new cost function based on the normalised MSPE is introduced which by design provides a unique solution to this class of BSE problems. Depending on whether the pre-whitening operation is required or not, a novel class of BSE algorithms are derived and approaches with both fixed and adaptive linear predictor coefficients are considered. The proposed algorithms are justified by both the analysis and simulation results     

A new limit on inter-element spacing for a linear array

This paper examines the issue of extending the aperture length of an equally-spaced linear array with a spacing beyond a half wavelength. Some empirical expressions are proposed to determine the array-aperture length and the array beamwidth, for both broadside and scanned arrays     

多元线性阵列超声换能器的方向特性研究

为了进一步提高多元线性阵列超声换能器的方向特性,采用多元相控聚焦的方法,研究了多元线性阵列超声换能器的主频、阵元个数和阵元间距对其方向性的影响。结果表明,当超声换能器的主频较低时,可以采用较大尺寸的阵元组;而对于主频较高的超声换能器,阵元尺寸应该取小一些,其方向性较好。这将有利于光声信号的探测与成像。     

The effect of a finite distance source on an Applebaum array

The effect of the finite distance of the signal source on the performance of a far-field steering Applebaum type adaptive array is examined. The output signal-to-noise ratio (SNR) is expressed in terms of 1) the distance between the signal and the array center, 2) the input SNR, 3) the element number and locations, and 4) the signal direction. From that expression a rule of thumb is drawn to determine the distance between the signal source and the array center at which the degradation of the output SNR is 1 dB. That distance is in general much larger than the far-field range of a conventional beam forming array.     

Mapping dynamic programming onto a linear systolic array

In the paper we show a single, efficient implementation of dynamic programming on alinear array using a new mapping methodology. In this method, we start with a known 2-D array onto which the dynamic programming algorithm has been mapped. By partitioning and stretching, this 2-D array is mapped onto a linear array. We derive a data movement scheme to simulate the data streams and the computations in the 2-D array. This scheme is implemented usingfast/slow data channels. Compared to known designs in the literature our design uses constant storage in each PE, constant number of I/O lines and continuous I/O sequence. Besides, the data and control flow in the array is unidirectional. This property makes the design suitable for implementation on the well-known fault-tolerant Wafer Scale Integration model.This research was supported in part by the National Science Foundation under grant IRI-8710836 and by AFOSR under grant AFOSR-0032.     

Shape calibration for a nominally linear equispaced array

We consider a thin flexible line array of equispaced hydrophones that is towed through the sea and develop a statistical test that allows us to decide whether the array is straight or not. The motion of the towing ship, the ocean currents and other forces induce deformations on the array and affect the performance of spatial processing of the data developed under the assumption that the array is straight. When the ship is maneuvering, the processing is generally turned off for long periods of time, an extremely penalizing situation that can be overcome by applying our scheme. Indeed, if the test-applied to the whole array-decides that it is out of shape, the same test is applied to parts of the array to determine the maximum size of admissible subarrays on which the standard processing can be pursued. By combining the bearings estimated by the different subarrays, we reconstruct a piecewise linear estimate of the shape of the array. The approach allows the handling of quite important deformations with no need for a cooperating source     

The orthogonal method for the geometry synthesis of a linearantenna array

The orthogonal method for geometry synthesis of a linear antenna array is presented. We start from an initial array, and we perturb the element positions by using an iterative procedure and applying the orthogonal method. Applications for arrays with uniform excitation give patterns with the desired sidelobe level     

均匀直线阵的波束形成

简述了单个信号和多个信号进入等距直 (天 )线阵列时波束形成的方法 ,分别用来自不同方向的 4个信号和 5个信号进入七个阵元的阵列进行试验 ,得出了仿真结果