检索结果-内蒙古大学图书馆

Model-Based Subspace Projection Beamforming for Deep Interference Nulling

IEEE TRANSACTIONS ON SIGNAL processing 2012年第3期60卷 1215-1228页

作者： Landon, Jonathan Jeffs, Brian D. Warnick, Karl F. L3 Commun Syst W Salt Lake City UT 84112 USA Brigham Young Univ Dept Elect & Comp Engn Provo UT 84602 USA

This paper considers the problem of adaptive array processing for interference canceling to drive very deep nulls in difficult signal environments. In many practical scenarios, the achievable null depth is limited by covariance matrix estimation error leading to poor identification of the interference subspace. We address the particularly troublesome cases of low interference-to-noise ratio (INR), relatively rapid interference motion, and correlated noise across the receiving array. A polynomial-based model is incorporated in the proposed algorithm to track changes in the array covariance matrix over time, mitigate interference subspace estimation errors, and improve canceler performance. The application of phased array feeds for radio astronomical telescopes is used to illustrate the problem and proposed solution. Here even weak residual interference after cancelation may obscure a signal of interest, so very deep beampattern nulls are required. Performance for conventional subspace projection (SP) is compared with polynomial-augmented SP using simulated and real experimental data, showing null-depth improvement of 6 to 30 dB.

关键词： adaptive array processing adaptive beamforming covariance estimation interference canceling phased array feeds radio astronomy subspace projection (SP)

来源：评论

学校读者我要写书评

暂无评论

Anti-Jamming GPS Receiver With Reduced Phase Distortions

引用

IEEE SIGNAL processing LETTERS 2012年第10期19卷 635-638页

作者： Zhang, Yimin D. Amin, Moeness G. Villanova Univ Wireless Commun & Positioning Lab Ctr Adv Commun Villanova PA 19085 USA

Anti-jamming techniques are critical to maintain the integrity and functionality of GPS systems in various applications. One of the major problems with existing array-based anti-jamming GPS receivers is the errors introduced in the carrier phase, affecting the GPS solution. In this letter, we propose a novel anti-jamming GPS receiver structure that preserves the GPS signal phase continuity. The effectiveness of the proposed technique is verified by simulation results.

关键词： adaptive array processing anti-jamming blind beamforming GPS receiver phase error

来源：评论

学校读者我要写书评

暂无评论

Development of an Experimental Phased array Feed System and Algorithms for Radio Astronomy

Development of an Experimental Phased Array Feed System and ...

引用

作者： Landon, Jonathan C. Brigham Young University

学位级别：Ph.D.

Phased array feeds (PAFs) are a promising new technology for astronomical radio telescopes. While PAFs have been used in other fields, the demanding sensitivity and calibration requirements in astronomy present unique new challenges. This dissertation presents some of the first astronomical PAF results demonstrating the lowest noise temperature and highest sensitivity at the time (66 Kelvin and 3.3 m 2/K, respectively), obtained using a narrowband (425 kHz bandwidth)prototype array of 19 linear co-polarized L-band dipoles mounted at the focus of the Green Bank 20 Meter Telescope at the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia. Results include spectral line detection of hydroxyl (OH) sources W49N and W3OH, and some of the first radio camera images made using a PAF, including an image of the Cygnus X region. A novel array Y-factor technique for measuring the isotropic noise response of the array is shown along with experimental measurements for this PAF. Statistically optimal beamformers (Maximum SNR and MVDR) are used throughout the work. Radio-frequency interference (RFI) mitigation is demonstrated experimentally using spatial cancelation with the PAF. Improved RFI mitigation is achieved in the challenging cases of low interference-to-noise ratio (INR) and moving interference by combining subspace projection (SP) beamforming with a polynomial model to track a rank 1 subspace. Limiting factors in SP are investigated including sample estimation error, subspace smearing, noise bias, and spectral scooping; each of these factors is overcome with the polynomial model and prewhitening. Numerical optimization leads to the polynomial subspace projection (PSP) method, and least-squares fitting to the series of dominant eigenvectors over a series of short term integrations (STIs) leads to the eigenvector polynomial subspace projection (EPSP) method. Expressions for the gradient, Hessian, and Jacobian are given for use in numerical optimization.

关键词： phased array feeds radio astronomy isotropic noise response array Y-factor method interference canceling adaptive array processing adaptive beamforming subspace projection subspace tracking covariance estimation CASPER ROACH FPGA astronomical back ends

来源：评论

学校读者我要写书评

暂无评论

High Resolution Ultrasound Imaging Using adaptive Beamforming with Reduced Number of Active Elements

High Resolution Ultrasound Imaging Using Adaptive Beamformin...

引用

International Congress on Ultrasonics

作者： Holfort, Iben Kraglund Gran, Fredrik Jensen, Jorgen Arendt Tech Univ Denmark Dept Elect Engn Ctr Fast Ultrasound Imaging DK-2800 Lyngby Denmark GN ReSound DK-2750 Ballerup Denmark

In this paper, the adaptive, minimum variance ( MV) beamformer is applied to ultrasound data. Due to near-field properties, the energy of the ultrasound data reduces towards the edges of the transducer. The influence of this near-field effect is demonstrated, and a method to reduce this influence is proposed. By reducing the number of active sensor elements, an increased resolution can be obtained with the MV beamformer. This observation is directly opposite the well-known relation between the spatial extent of the aperture and the achievable resolution. The investigations are based on Field II simulated data using a 128-element transducer with a large spatial extent. The results show that an increased resolution can be obtained, when using only the central part of the transducer compared to using the entire spatial extent. Using the central 32 or 48 elements provides an increased resolution compared to using all 128 elements.

关键词： adaptive array processing adaptive Beamforming High Resolution Beamforming Minimum Variance Beamforming Ultrasound Imaging

来源：评论

学校读者我要写书评

暂无评论

High resolution ultrasound imaging using adaptive beamforming with reduced number of active elements

引用

Physics Procedia 2010年第1期3卷 659-665页

作者： Iben Kraglund Holfort Fredrik Gran Jørgen Arendt Jensen Technical University of Denmark Dept. Electrical Engineering Center for Fast Ultrasound Imaging DK-2800 Kgs. Lyngby Denmark GN ReSound A/S Lautrupvej 7 DK-2750 Ballerup Denmark

In this paper, the adaptive, minimum variance (MV) beamformer is applied to ultrasound data. Due to near-field properties, the energy of the ultrasound data reduces towards the edges of the transducer. The influence of this near-field effect is demonstrated, and a method to reduce this influence is proposed. By reducing the number of active sensor elements, an increased resolution can be obtained with the MV beamformer. This observation is directly opposite the well-known relation between the spatial extent of the aperture and the achievable resolution. The investigations are based on Field II simulated data using a 128-element transducer with a large spatial extent. The results show that an increased resolution can be obtained, when using only the central part of the transducer compared to using the entire spatial extent. Using the central 32 or 48 elements provides an increased resolution compared to using all 128 elements.

关键词： adaptive array processing adaptive beamforming High resolution beamforming Minimum variance beamforming Ultrasound imaging

来源：评论

学校读者我要写书评

暂无评论

adaptive array processing for wide-band active sonars

引用

IEEE JOURNAL OF OCEANIC ENGINEERING 2004年第3期29卷 837-846页

作者： Lo, KW Def Sci & Technol Org Maritime Operat Div Pyrmont NSW 2009 Australia

A high-frequency sector scan sonar can be used to detect and classify man-made objects located on the sea floor. If the hydrophone array of the sonar is to be mounted on a miniaturized autonomous underwater vehicle, the aperture size of the array must be small enough so that it will not affect the vehicle's maneuverability. However, a small aperture size of the array results in poor angular resolution when using the conventional delay and sum beamforming technique. This paper shows that, with the aid of spatial resampling, narrow-band adaptive beamforming algorithms can be applied to improve the angular resolution of wide-band active sonars with a small aperture uniform linear hydrophone array. Owing to the motion of the vehicle and the highly nonstationary environment, only single-snapshot adaptive beamforming algorithms can be used. In this paper, spatial smoothing is used in conjunction with the minimum variance distortionless response and multiple signal classification adaptive beamforming algorithms to produce a high-resolution image using a single ping. Real sonar images generated using these two algorithms are compared with those generated using another single-snapshot adaptive beamforming algorithm, spatial processing: optimized and constrained, and the conventional delay and sum beamforming algorithm.

关键词： adaptive array processing adaptive beamforming single snapshot spatial resampling spatial smoothing wide-band active sonar

来源：评论

学校读者我要写书评

暂无评论

adaptive array processing for high-speed acoustic communication in shallow water

引用

IEEE JOURNAL OF OCEANIC ENGINEERING 2004年第3期29卷 807-823页

作者： Beaujean, PPJ LeBlanc, LR Florida Atlantic Univ Dept Ocean Engn Dania FL 33004 USA

A novel multichannel signal-processing technique, capable of achieving stable high-speed underwater acoustic communication with a fairly low complexity of implementation, is presented. The approach is to split the space and time processing into two separate suboptimal processes to reduce computational complexity and instabilities associated with large tap vectors at large spread factors or BL products. The first suboptimal process starts with the eigen-spatial decomposition of the acoustic channel into multiple coherent orthogonal paths. Only the most energetic coherent paths are retained. For each selected path, individual synchronization is performed, the mean Doppler shift is estimated, and the message is decoded. The message binary information obtained for each individual path is recombined using maximal-ratio combining (MRC) to generate a decision binary sequence along with an array of quality factors, or metrics, associated with each bit. Each metric corresponds to the signal-to-noise-and-interference ratio (SNIR) associated with each bit. The second suboptimal process is a linear multichannel equalizer (LME). The mean Doppler estimate of the most energetic coherent path is used to resample each input signal of the array that go into the LME, to reduce the rate of fluctuation of the resulting effective channel. These resampled input signals appear as if they have passed through a channel with a lower B (Doppler spread), which allows the final space-time processor (the LME) to operate in a stable manner. The decision binary sequence and the array of quality metrics obtained at the output of the AIRC are used as inputs in the decision process of the LME. If the metric associated with a decision bit exceeds a computed threshold, this bit, obtained at the output of the first suboptimal process, is used as a decision input to the LME. This technique is applied to achieve high-speed acoustic communication in very shallow water using coherent modulation techniques. A

关键词： acoustic communication adaptive array processing spread factor

来源：评论

学校读者我要写书评

暂无评论

Improved smart antenna design using displaced sensor array configuration

引用

APPLIED COMPUTATIONAL ELECTROMAGNETICS SOCIETY JOURNAL 2007年第1期22卷 83-87页

作者： Shubair, Raed M. Etisalat Univ Coll Dept Commun Engn Sharjah U Arab Emirates

In this paper we propose a new sensor array configuration for improved smart antenna design. The new configuration involves two parallely-displaced sensor arrays in the vertical plane. The proposed sensor array configuration avoids the problem of spatial aliasing encountered in largely spaced sensor arrays and reduces the effects of inter-element mutual coupling for closely spaced arrays. Moreover, the proposed sensor array configuration allows for doubling the number of array elements and, hence, increasing the system capacity, without significantly increasing the array aperture. This allows for a more accurate beam pattern to be generated especially in a radio environment with a large number of interference signals. Numerical results are presented to demonstrate the improved performance of direction-of-arrival estimation and adaptive beamforming algorithms when the proposed array configuration is used.

关键词： smart antennas adaptive array processing direction-of-arrival estimation adaptive beamforming

来源：评论

学校读者我要写书评

暂无评论

Ionospheric clutter suppression in HF surface wave radar OSMAR

Ionospheric clutter suppression in HF surface wave radar OSM...

引用

7th International Symposium on Antennas, Propagation and EM Theory

作者： Wan Xianrong Xiong Xinlong Ke Hengyu Wuhan Univ Sch Elect Informat Hubei 430079 Peoples R China

ISBN: (纸本)9781424401628

Experimental trials conducted from 2003 to 2005 in east China sea demonstrated that HF surface wave radar (HFSWR) OSMAR (Ocean State Monitor and Analysis Radar) could be strongly affected by scattering from ionospheric structures and irregularities. A large database acquired during those trials has been used in detailed investigations of the phenomenology of this ionospheric clutter, leading to the development of effective mitigation techniques based on the characteristics of ionospheric clutter. In this paper the 2-D angle of arrival of ionospheric clutter has been analyzed and the spatial adaptive processing based on 2-D antenna array is introduced to suppress ionospheric clutter. Experimental results confirm that the above technique can achieve effective ionospheric clutter suppression using the field experimental data recorded by the OSMAR2003.

关键词： HF surface wave radar ionospheric clutter adaptive array processing

来源：评论

学校读者我要写书评

暂无评论

The adaptive coherence estimator: A uniformly most-powerful-invariant adaptive detection statistic

引用

IEEE TRANSACTIONS ON SIGNAL processing 2005年第2期53卷 427-438页

作者： Kraut, S Scharf, LL Butler, RW Queens Univ Dept Math & Stat Kingston ON K7L 3N6 Canada Queens Univ Dept Elect & Comp Engn Kingston ON K7L 3N6 Canada Colorado State Univ Dept Elect & Comp Engn Ft Collins CO 80523 USA Colorado State Univ Dept Stat Ft Collins CO 80523 USA

We show that the adaptive Coherence Estimator (ACE) is a uniformly most powerful (UMP) invariant detection statistic. This statistic is relevant to a scenario appearing in adaptive array processing, in which there are auxiliary, signal-free, training-data vectors that can be used to form a sample covariance estimate for clutter and interference suppression. The result is based on earlier work by Bose and Steinhardt, who found a two-dimensional (2-D) maximal invariant when test and training data share the same noise covariance. Their 2-D maximal invariant is given by Kelly's Generalized Likelihood Ratio Test (GLRT) statistic and the adaptive Matched Filter (AMF). We extend the, maximal-invariant framework to the problem for which the ACE is a GLRT: The test data shares the same covariance structure as the training data, but the relative power level is not constrained. In this case, the maximal invariant statistic collapses to a one-dimensional (1-D) scalar, which is also the ACE statistic. Furthermore, we show that the probability density function for the ACE possesses the property of "total positivity," which establishes that it has. monotone likelihood ratio. Thus, a threshold test on the ACE is UMP-invariant. This means that it has a claim to optimality, having the largest detection probability out of the class of detectors that are also invariant to affine transformations on the data matrix that leave the hypotheses unchanged. This requires an additional invariance not imposed by Bose and Steinhardt: invariance to relative scaling of test and training data. The ACE is invariant and has a Constant False Alarm Rate (CFAR) with respect to such scaling, whereas Kelly's GLRT and the AMF are invariant, and CFAR, only with respect to common scaling.

关键词： adaptive detection adaptive coherence estimator adaptive rador and sonar adaptive array processing constant false alarm rate invariant detection sample convariance uniformly most powerful invariant

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：