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ON THE STABILITY OF ADAPTIVE ANTENNA-ARRAYS WITH WEIGHTS AT AN INTERMEDIATE-FREQUENCY

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 1992年第11期40卷 1438-1444页

作者： BOUKTACHE, E Department of Electrical Engineering Technology Purdue University Calumet Hammond IN USA

This paper focuses on the stability problem that exists in adaptive antenna arrays when the weighting functions operate at a nonzero frequency. It begins with the application of the LMS algorithm when the weights are written in terms of an in-phase and a quadrature component. The behavior of the signal processing algorithm is then described by a set of coupled differential equations which are derived under zero-delay conditions. When time delays that may be present in the feedback loops due to filtering are taken into account, the stability and therefore the performance of the array are greatly affected. This paper shows how stability can be achieved by a simple time-compensation procedure. Simulation results show that interference rejection comparable to the zero-delay case is experienced. The importance of this study is twofold: 1) it is an analytical supplement to an experimental array built with the same type of weights, and 2) it provides the condition of stability that will allow a digital implementation of the weight processor.

关键词： Signal processing algorithms Feedback loop WEIGHTING FUNCTIONS adaptive antenna arrays Antenna arrays quadrature component suppression of interference least mean square algorithm Differential equations Intermediate frequencies stability problems

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Design of thinned fractal antenna arrays for adaptive beam forming and sidelobe reduction

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IET MICROWAVES ANTENNAS & PROPAGATION 2018年第3期12卷 435-441页

作者： El-Khamy, Said E. Eltrass, Ahmed S. El-Sayed, Huda F. Alexandria Univ Dept Elect Engn Alexandria 21544 Egypt Pharos Univ Dept Basic Sci Alexandria Egypt

This study introduces, for the first time, a new design methodology that combines the unique multi-band features of thinned fractal antenna arrays with the adaptive beamforming requirements. The major challenges of fractal array design are the high sidelobe level (SLL), the huge number of elements at higher-growth stages, and the radiation pattern synthesis. In this study, the ant colony optimisation algorithm is utilised for thinning fractal arrays by estimating the optimum combination of on' and off' elements corresponding to lowest possible SLL, while the least mean square algorithm is investigated as an adaptive beamforming method in the proposed design. The capability of the proposed design is demonstrated by investigating hexagonal and pentagonal fractal antenna arrays under various parameter regimes. The results show that the proposed design is much superior in terms of multi-band frequency operation, array element reduction, and beamforming accuracy. This reveals the effectiveness of the proposed technique as a promising design in smart antenna technology.

关键词： fractal antennas array signal processing antenna radiation patterns ant colony optimisation least mean squares methods adaptive antenna arrays thinned fractal antenna arrays adaptive beam forming method sidelobe reduction multiband features fractal array design high sidelobe level radiation pattern synthesis ant colony optimisation algorithm least mean square algorithm pentagonal fractal antenna arrays hexagonal fractal antenna arrays multiband frequency operation array element reduction smart antenna technology

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Advances in Capacitor Health Monitoring Techniques for Power Converters: A Review

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IEEE ACCESS 2023年 11卷 133540-133576页

作者： Ramees, M. K. P. Muhammed Ahmad, Md. Waseem Natl Inst Technol Karnataka Mangalore 575025 India

Capacitors play a critical role in power electronic systems, and their health and performance directly impact system reliability and efficiency. This article provides an overview of advanced techniques developed for capacitor monitoring, focusing on diagnosing, estimating, and predicting capacitor health in various power electronic converters. The condition monitoring techniques are categorized based on the type of converter, and a comprehensive review and comparison of various methods are provided within each category. The article covers various techniques, including impedance spectroscopy, frequency response analysis, harmonic analysis, wavelet analysis, short-time Fourier transform, and algorithm-based predictive models. These techniques enable early detection of capacitor faults, accurate estimation of capacitance and equivalent series resistance (ESR), and prediction of the remaining useful life of capacitors. By implementing these advanced monitoring techniques, engineers and researchers can enhance system reliability, prevent unexpected failures, and optimize maintenance and replacement strategies for capacitors in power electronic systems.

关键词： Condition monitoring equivalent series resistance least mean square algorithm support vector machine

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An acoustic feedback canceler based on probe noise and informative data for hearing aids

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SIGNAL IMAGE AND VIDEO PROCESSING 2024年第1期18卷 703-714页

作者： Eren, Yusuf Guvenc, Buket Colak Menguc, Engin Cemal Erciyes Univ Dept Elect & Elect Engn Kayseri Turkiye Kayseri Univ Dept Elect & Elect Engn Kayseri Turkiye

One of the important issues encountered in acoustic feedback canceler (AFC) systems is the bias occurring in the estimation of the acoustic feedback (AF) path. In the literature, a common solution is to inject the probe noise into the loudspeaker to reduce the correlation between the input signal and the loudspeaker signal, that is, to remove the bias occurring in the estimation of the AF path. This approach significantly improves the performance of the AFC systems. However, when considering high filter orders and large-scale input signals, the AFC systems suffer from the data processing cost, and thus their real-time implementations on a chip generally become challenging. To this end, in this paper, we propose an AFC system using jointly probe noise and informative data, named the probe noise-online censoring-least mean square (PN-OC-LMS) based AFC. Thanks to both the OC mechanism and the probe noise injection approach, the proposed PN-OC-LMS-based AFC system not only significantly reduces the data processing cost but also effectively removes the bias effect in the AF path. The mentioned effectiveness of the proposed AFC system is supported by three comprehensive experiments on a real-world AF path measured from a behind-the-ear hearing aid. As a result, in the proposed AFC system, the use of both informative data and the injection of probe noise will enable the design of a long-term working wearable hearing aid that provides low data processing cost and correctly estimates the AF path.

关键词： Acoustic feedback canceler Online censoring strategy least mean square algorithm Adaptive filter Probe noise injection

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A novel LMS algorithm for ECG signal preprocessing and KNN classifier based abnormality detection

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MULTIMEDIA TOOLS AND APPLICATIONS 2018年第8期77卷 10365-10374页

作者： Venkatesan, C. Karthigaikumar, P. Varatharajan, R. Anna Univ Fac Informat & Commun Engn Chennai Tamil Nadu India Karpagam Coll Engn Dept Elect & Commun Engn Coimbatore Tamil Nadu India Sri Ramanujar Engn Coll Dept Elect & Commun Engn Chennai Tamil Nadu India

ECG signal abnormality detection is useful for identifying heart related problems. Two popular abnormality detection techniques are ischaemic beat classification and arrhythmic beat classification. In this work, ECG signal preprocessing and KNN based arrhythmic beat classification are performed to categorize into normal and abnormal subjects. LMS based adaptive filters are used in ECG signal preprocessing, but they consume more time for processing due to long critical path. To overcome this problem, a novel adaptive filter with delayed error normalized LMS algorithm is utilized to attain high speed and low latency design. Low power design is achieved in this design by applying pipelining concept in the error feedback path. R-peak detection is carried out in the preprocessed signal using wavelets for HRV feature extraction. Arrhythmic beat classification is carried out by KNN classifier on HRV feature extracted signal. Classification performance reveals that the proposed DWT with KNN classifier provides the accuracy of 97.5% which is better than other machine leaning techniques.

关键词： ECG noise removal Adaptive filter least mean square algorithm Discrete wavelet transform Machine learning KNN classifier

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Efficient adaptive complex filtering algorithm with application to channel equalisation

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IEE PROCEEDINGS-VISION IMAGE AND SIGNAL PROCESSING 1999年第2期146卷 57-64页

作者： Perry, R Bull, DR Nix, A Univ Bristol Ctr Commun Res Bristol BS8 1TR Avon England

The paper describes a means of efficiently implementing an adaptive complex transversal filter. Three real-coefficient filter sections are used to realise the transversal filter section of a complex equaliser, thus using one less filter than a conventional realisation. An adaptive algorithm is developed, in a manner similar to the least mean square algorithm, which allows the three filters to be trained independently and in parallel using real valued arithmetic. In this way, throughput can be maintained, whilst reducing the number of multipliers in both the filter and coefficient update sections by 25%. Using independence theory, it is demonstrated that the three filters converge to a solution consistent with the optimal Wiener-Hopf solution. The convergence speed is characterised in terms of the complex input data stream. The transient behaviour of the algorithm is examined using a simulation of a channel equaliser and is supported by analysis.

关键词： adaptive filters adaptive signal processing adaptive algorithm Digital signal processing convergence speed digital arithmetic coefficient update transient behaviour efficient adaptive complex filtering algorithm multipliers least mean square algorithm complex input data stream Filtering methods in signal processing optimal Wiener-Hopf solution real valued arithmetic adaptive equalisers Communication channel equalisation and identification adaptive complex transversal filter simulation convergence of numerical methods Digital arithmetic methods throughput real-coefficient filter sections channel equalisation gradient based training algorithm independence theory

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A robust interference cancellation technique for DS-UWB systems using fuzzy step size LMS algorithm

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EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS 2008年第2期19卷 207-217页

作者： Cheng, Chia-Hsin Wen, Jyh-Horng Chen, Yu-Fan Lin, Jen-Yung Natl Chung Cheng Univ Dept Elect Engn Inst Elect Engn Chiayi 621 Taiwan Natl Chung Cheng Univ Inst Commun Engn Chiayi 621 Taiwan Tunghai Univ Dept Elect Engn Taichung 40704 Taiwan Da Yeh Univ Dept Comp Sci & Informat Engn Da Tsuen 515 Chang Hua Taiwan

This paper discusses a direct-sequence ultra-wideband (DS-UWB) system that uses the least mean square (LMS) adaptive filter for interference cancellation. Compared to the conventional LMS (C-LMS) algorithm, the fuzzy step size LMS (FSS-LMS) algorithm which we propose can perform rapid convergence with a low steady-state fluctuation error. The sequential partial update scheme is used in the proposed FSS-LMS algorithm to reduce the system complexity without trading off the bit error rate (BER). Simulations are conducted to evaluate the convergence and tracking behaviour of the proposed LMS algorithm. The BER of the DS-UWB system in a realistic UWB channel is also investigated. Copyright (C) 2007 John Wiley & Sons, Ltd.

关键词： Converge learning management system Interference cancellation step size DS-UWB Ultra wideband technologies Bit error rate Fuzzy Levamisole least mean square algorithm

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Adaptive algorithm for active control of impulsive noise

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JOURNAL OF SOUND AND VIBRATION 2006年第1-2期291卷 516-522页

作者： Sun, X Kuo, SM Meng, GA No Illinois Univ Dept Elect Engn Vibrat & Acoust Ctr De Kalb IL 60115 USA Shanghai Jiao Tong Univ State Key Lab Vibrat Shock & Noise Shanghai 200030 Peoples R China

When active noise control (ANC) systems are applied for reducing impulsive noise, conventional adaptive algorithms for ANC may not be effective. In this paper, a new adaptive algorithm for active control of impulsive noise is presented. Compared to the filtered-x least-mean-square algorithm, the proposed algorithm has a much better convergence and stability. Illustrative simulations are conducted to verify the proposed algorithm. (c) 2005 Elsevier Ltd. All rights reserved.

关键词： active control Adaptive algorithms Acid neutralising capacity Impulse noise least mean square algorithm Self tuning

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Variable step-size LMS algorithm for estimation of time-varying and frequency-selective channels

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ELECTRONICS LETTERS 2004年第20期40卷 1312-1313页

作者： Arraes Filho, AM Pinto, EL Galdino, JF IME Dept Engn Eletr Lab Comunicacoes Digitais BR-22290270 Rio De Janeiro Brazil

A new strategy is proposed for deriving a variable step-size least mean squares (VSS-LMS) algorithm suited for the estimation of time-varying and frequency-selective communications channels modelled as wide sense stationary channels-uncorrelated scattering (WSS-US). The variable step size is obtained by minimising the analytical expression of the mean square weight estimation error as a function of time. Computer simulation results are presented which show that the new VSS-LMS algorithm so obtained produces performance gains in relation to the conventional LMS algorithm and for some channel models may also outperform the recursive least squares algorithm.

关键词： Communication channel equalisation and identification Filtering methods in signal processing least mean square algorithm adaptive filters computer simulation channel estimation LMS algorithm wide sense stationary channels-uncorrelated scattering time-varying channels channel models time varying channels frequency-selective communications channels digital simulation mean square weight estimation error least mean squares methods

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Blind adaptive channel mismatch equalisation method for GNSS antenna arrays

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IET RADAR SONAR AND NAVIGATION 2018年第4期12卷 383-389页

作者： Lu, Zukun Chen, Huaming Chen, Feiqiang Nie, Junwei Ou, Gang Natl Univ Def Technol Coll Elect Sci 109 Deya Rd Changsha Hunan Peoples R China

A blind adaptive channel mismatch equalisation method for global navigation satellite system (GNSS) antenna arrays is proposed. The anti-jamming performance of the antenna arrays is limited by the channel mismatch that is a relative characteristic of each radio frequency channel but not an absolute non-ideal characteristic. To pre-process the received data in the frequency domain, the least mean square (LMS) algorithm is used. The reference signal in LMS is the received data in the reference element. The purpose of pre-processing is to make the received data in the other elements approach the reference signal, which, in essence, is to equalise the mismatched channel. Without any auxiliary sensors and calibration source, this method can estimate the channel characteristics relative to the reference elements. Simulations and experimental results show that the proposed method is significant in improving the anti-jamming performance.

关键词： channel estimation blind equalisers adaptive equalisers satellite navigation satellite antennas antenna arrays jamming interference suppression least mean squares methods frequency-domain analysis blind adaptive channel mismatch equalisation method GNSS antenna array Global Navigation Satellite System antijamming performance radiofrequency channel least mean square algorithm LMS algorithm frequency domain algorithm auxiliary sensor calibration source channel estimation

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