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Fast adaptive microwave beamforming using array signal estimation

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 2007年第3期55卷 850-858页

作者： Farzaneh, Sadegh Sebak, Abdel-Razik Concordia Univ Dept Elect & Comp Engn Montreal PQ H4G 2W1 Canada

A new perturbation technique is proposed which enables adaptive beamforming (ABF) in microwave domain using a single-port beamformer. In this technique, for a system with L antennas, the weight vector is independently perturbed L times to obtain L correlated outputs. These outputs are then used to find a noisy approximation of the antenna array signal for the gradient vector estimation. The process of weight perturbations is performed faster than the Nyquist rate mainly to increase the temporal correlation of the consecutive antenna array signal samples and to lower the perturbation error. Performance of the proposed perturbation technique with the adaptive unconstrained least mean square (ULMS) algorithm is investigated for different channel scenarios. The ULMS algorithm with single-port beamformer converges in very high noise and interference levels and with a convergence speed close to that of the multi-port receiver. After convergence, both the single-port and the multiport beamformer algorithms achieve the same steady state signal to interference plus noise ratio (SINR) gain. Effects of weight quantization are also investigated for the single-port beamformer with the proposed perturbation technique.

关键词： adaptive beamforming (ABF) digital beamforming (DBF) microwave beamforming (MBF) perturbation algorithms

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An Optimum Adaptive Single-Port Microwave Beamformer Based on Array Signal Vector Estimation

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IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 2010年第3期58卷 738-746页

作者： Farzaneh, Sadegh Sebak, Abdel-Razik Ecole Polytech Dept Elect & Comp Engn Montreal PQ H3C 3A7 Canada Concordia Univ Dept Elect & Comp Engn Montreal PQ H3G 1M8 Canada

A single-port adaptive beamforming structure based on an optimum perturbation technique is presented. The proposed perturbation technique is based on array signal vector estimation for temporally-correlated array signals. Temporal correlation is generated by jointly reducing the receiver bandwidth and increasing the weighting rate. The error signal is generated using the estimated array signal vector that is estimated in (L + 1) perturbation cycles for an L-element array. The proposed perturbation technique with the adaptive unconstrained least mean square (ULMS) algorithm achieves a lower misadjustment than previous perturbation techniques and the multi-port ULMS algorithm. With proper gradient step size variations and/or weight clipping the proposed algorithm converges with a larger maximum gradient step size than the multi-port and other single-port algorithms. The new perturbation technique can be implemented with less hardware complexity and speed than previous techniques.

关键词： Adaptive beamforming digital beamforming microwave beamforming multi-port structure perturbation algorithms single-port structure

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Ho's theorem in global-local mode interaction of pin-jointed bar structures

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INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS 2006年第3期41卷 359-376页

作者： Salerno, G Uva, G Univ Roma Tre Dept Struct I-00146 Rome Italy Politech Univ Bari Dept Sci Civil Engn & Architecture I-70125 Bari Italy

This paper is focused on the interaction phenomena among a global critical mode and some local Eulerian critical modes in pin-jointed structures. These phenomena are framed within Koiter's theory of elastic instability, by an asymptotic reduction into cubic systems. The aim is to present an algorithm for the appraisal of the lowest critical load characterizing the structure under the effect of small imperfections. First of all, the Ho's theorem, concerning the definition of the most dangerous imperfection, is presented and discussed. Then, a FEM code aimed at the determination of the most dangerous shape for the imperfection, and at performing the related sensitivity analysis, is implemented, by superimposing a proper FE beam model (able to model Eulerian instability) to a non-linear FE model for spatial pin-jointed structures. Some numerical results having a practical interest are presented and discussed. (c) 2005 Elsevier Ltd. All rights reserved.

关键词： slender elastic structures perturbation algorithms global-local modal interaction FE analysis

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ADAPTIVE ARRAY-PROCESSING USING THE DAVIES BEAMFORMER

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IEE PROCEEDINGS-H MICROWAVES ANTENNAS AND PROPAGATION 1986年第6期133卷 467-473页

作者： KO, CC Department of Electrical Engineering National University of Singapore Singapore Singapore

The paper presents and analyses a simple and fast adaptive array based on the Davies null-steering beamformer [1]. The use of perturbation algorithms on this beamformer is investigated. The convergence time constants and misadjustment are derived. It is shown that, if the feedback factors for these algorithms are appropriately normalised, the time constants can be roughly equalised, resulting in fast convergence behaviour.

关键词： misadjustment Antenna theory adaptive array antenna radiation patterns feedback factors antenna phased arrays convergence time constants null-steering beamformer Davies beamformer Antenna arrays perturbation algorithms antenna theory

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Adaptive Microwave Beamforming using High Weighting Rate and ULMS Algorithm

Adaptive Microwave Beamforming using High Weighting Rate and...

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64th IEEE Vehicular Technology Conference

作者： Farzaneh, S. Sebak, A. R. Concordia Univ Montreal PQ Canada

ISBN: (纸本)9781424400621

In this work adaptive beamforming (ABF) is carried out for the general microwave beamformer using a new perturbation technique. For an L-element antenna array, the weight vector is perturbed L+1 times sequentially to obtain a noisy approximation of the antenna array signals for the gradient vector estimation. The process of weight perturbation is performed faster than the Nyquist rate to increase the temporal correlation between the signal samples in different perturbation cycles to decrease the gradient estimation error. The unconstrained least mean square (ULMS) algorithm is studied with the proposed perturbation technique. The proposed algorithm converges as fast as the corresponding digital beamforming algorithm in very low signal to noise ratio (SNR) and signal to interference ratio (SIR) conditions.

关键词： perturbation algorithms microwave beamforming adaptive beamforming

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Optimization as generator of structural instability: Koiter's worst imperfection

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THIN-WALLED STRUCTURES 2023年 192卷

作者： Salerno, Ginevra Univ Roma Tre Dept Architecture Via Madonna de Monti 40 I-00186 Rome Italy

This paper is focused on the interaction of local modes in pin-jointed structures, with the aim to present an algorithm for the appraisal of the lowest critical load characterizing the structure under the effect of small imperfections. This interaction phenomenon is framed within Koiter's theory of elastic instability as a quartic system. First of all, the paper discusses the theoretical results of Koiter's theorem about the determination of the worst imperfection with respect to the critical load. In doing this, the characterization of the fold lines in the modal space is recalled and used for the purposes of the reformulation of the theorem. Then, a FEM code aimed at the determination of the most dangerous shape of the imperfection, and at performing the related sensitivity analysis, is presented. The basis of the code is a nonlinear model of a 3D rod equipped with a planar flexural deformation, within the context of Eulerian instability. Some numerical results having a practical interest are discussed.

关键词： Slender elastic structures perturbation algorithms Local mode interaction Worst imperfection Fold lines Sensitivity analysis Finite elements

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