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window functions for imaging radar: a maximum energy approach to contiguous and notched spectrums

OPTICAL ENGINEERING 2003年第7期42卷 2113-2128页

作者： Dickey, FM Romero, LA Doerry, AW Sandia Natl Labs Albuquerque NM 87185 USA

Imaging systems such as synthetic aperture radar collect band-limited data from which an image of a target scene is rendered. The band-limited nature of the data generates sidelobes, or spilled energy, most evident in the neighborhood of bright point-like objects. It is generally considered desirable to minimize these sidelobes, even at the expense of some generally small increase in system bandwidth. This is accomplished by shaping the spectrum with window functions prior to inversion or transformation into an image. A window function that minimizes sidelobe energy can be constructed based on prolate spheroidal wave functions. A parametric design procedure allows doing so, even with constraints on allowable increases in system bandwidth. This approach is extended to accommodate spectral notches or holes, although the guaranteed minimum sidelobe energy can be quite high in this case. Interestingly, for a fixed bandwidth, the minimum mean-squared-error image rendering of a target scene is achieved with no windowing at all (rectangular or boxcar window). (C) 2003 Society of Photo-Optical Instrumentation Engineers.

关键词： synthetic aperture radar sidelobes window functions filtering notched spectrum

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window functions in Rhythm Based Biometric Authentication 8th

Window Functions in Rhythm Based Biometric Authentication

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8th International Work-Conference on Bioinformatics and Biomedical Engineering (IWBBIO)

作者： Alpar, Orcan Krejcar, Ondrej Univ Hradec Kralove Fac Informat & Management Ctr Basic & Appl Res Rokitanskeho 62 Hradec Kralove 50003 Czech Republic

ISBN: (纸本)9783030453848;9783030453855

Emerging new technologies and new threads entail additional security;therefore, biometric authentication is the key to protecting the passwords by classifying unique biometric features. One of the protocols recently proposed is the rhythm-based authentication dealing with the dominant frequency components of the keystroke signals. However, frequency component itself is not enough to understand the whole keystroke sequence;therefore, the characteristic of a password could only be analyzed by transformations providing the information of when which dominant frequency arises. In this paper, the biometric signal generated from keystroke data is divided into windows by various window functions and sizes for frequency and time localization. As a guide for signal processing in biometrics and biomedicine, we compared Hamming and Blackman widow functions with various sizes in short time Fourier transformations of the signals and found out that Blackman is more appropriate for biometric signal processing.

关键词： Biometrics Signals Authentication Security Frequency window functions

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A Rapid Single-view Radar Imaging Method with window functions

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APPLIED COMPUTATIONAL ELECTROMAGNETICS SOCIETY JOURNAL 2024年第1期39卷 1-8页

作者： Yu, Wen Ming Yang, Yi Ting Lu, Xiao Fei Yang, Chao Chen, Zai Gao Cui, Tie Jun Southeast Univ Sch Informat Sci & Engn Nanjing 210096 Peoples R China Jiuquan Satellite Launch Ctr Jiuquan 732750 Peoples R China Northwest Inst Nucl Technol Xian 710024 Peoples R China

Monostatic rapid single -view radar imaging technology is a technique that employs single incidence angle and single frequency point information to implement rapid monostatic radar imaging within a small angular field. Owing to its analytical expression, this technique can substitute the traditional frequencyangle -scanning imaging in a small angular range, facilitating the rapid generation of highly realistic radar imaging data slices for complex targets and environments. This technology has been significantly applied in scatter hotspot diagnostics and target recognition. In order to achieve the windowing effect equivalent to that of frequency -angle -scanning imaging, and to enhance the scattering feature of monostatic imaging while controlling sidelobes, this paper derives analytic windowed imaging formulas for monostatic radar. It then obtains analytical expressions for various typical monostatic windowing rapid radar imaging scenarios. This enables the monostatic rapid imaging technology to maintain high efficiency in its analytical expressions while achieving the windowing effect equivalent to traditional imaging. The validity and correctness of the analytical formula and software implementation have been confirmed through 1D, 2D, and 3D imaging verifications. This technology can provide a vast amount of training data for modern radars.

关键词： Radar imaging single-view window functions

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Distributed Brillouin optical fiber sensors assisted by first -order Raman with window functions

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OPTICS AND LASERS IN ENGINEERING 2023年第1期164卷

作者： Huang, Qiang Bao, Yuben Sun, JunQiang Huang, Chukun Huazhong Univ Sci & Technol Sch Opt & Elect Informat Wuhan Natl Lab Optoelect Wuhan Hubei Peoples R China Shaoyang Univ Sch Elect Engn Shaoyang Hunan Peoples R China

Raman amplification can extend the sensing distance of distributed Brillouin optical fiber sensor, and there is a corresponding relationship between the optimal Raman pump, the sensing distance, and the lanched probe power. We propose a scheme of co-directional Raman pumping Brillouin optical time-domain reflectometer (BOTDR) with window functions to make a better tradeoff between sensing distance and signal-to-noise ratio (SNR). The mathematical model of window functions is designed based on the relationship between the sensing distance and Raman pump power. Both simulations and experiments analyze the distributions of Brillouin scattering power, which are detected under the fixed Raman pump and processed by the window functions. We then obtain the Brillouin frequency shift (BFS) distribution curve by Lorentzian curve fitting. The experimental results show that the system SNR is increased by 3.3 dB at the near-end of the 78.8 km long sensing fiber. Moreover, the accuracy of temperature and strain at the far-end is enhanced by 2.75 degrees C and 389 mu epsilon by using window functions, respectively.

关键词： Fiber optics sensors Raman amplification BOTDR window functions SNR

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Design of ultraspherical window functions with prescribed spectral characteristics

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EURASIP JOURNAL ON APPLIED SIGNAL PROCESSING 2004年第13期2004卷 2053-2065页

作者： Bergen, SWA Antoniou, A Univ Victoria Dept Elect & Comp Engn Victoria BC V8W 3P6 Canada

A method for the design of ultraspherical window functions that achieves prescribed spectral characteristics is proposed. The method comprises a collection of techniques that can be used to determine the three independent parameters of the ultraspherical window such that a specified ripple ratio and main-lobe width or null-to-null width along with a user-defined side-lobe pattern can be achieved. Other known two-parameter windows can achieve a specified ripple ratio and main-lobe width;however, their side-lobe pattern cannot be controlled as in the proposed method. A comparison with other windows has shown that a difference in performance exists between the ultraspherical and Kaiser windows, which depends critically on the required specifications. The paper also highlights some applications of the proposed method in the areas of digital beamforming and image processing.

关键词： window functions ultraspherical window beamforming image processing digital filters

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The design of multi-dimensional acoustic beamformers via window functions

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DIGITAL SIGNAL PROCESSING 2014年第1期29卷 107-116页

作者： Feng, Zhi Guo Yiu, Ka Fai Cedric Chongqing Normal Univ Coll Math Chongqing Peoples R China Hong Kong Polytech Univ Dept Appl Math Kowloon Hong Kong Peoples R China

The design of broadband beamformers can be formulated as a semi-infinite programming optimization problem, where the coefficients of the filters are determined such that the actual response of the microphone array is near a given desired response. This problem can be solved by existing optimization solvers after the discretization of the infinite constraints. However, this problem will become large-scale and it's expensive to find the optimal solution, as the discretization points grow and the filter length increases. In this paper, we propose a fast method based on the window functions. First, we formulate a simplified optimization problem to find the limit of the cost function values as the filter length is sufficiently long. Hence, the optimal frequency response vector is obtained and the corresponding filter coefficients can be calculated. Second, we apply the window method to truncate the limiting filter to obtain a finite FIR filters. The performance as well as the computational complexity are investigated to demonstrate the effectiveness and efficiency of the proposed method. (C) 2014 Elsevier Inc. All rights reserved.

关键词： Multi-dimensional beamformers Nearfield beamformers window functions Fast beamformer design Semi-infinite programming

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An efficient closed-form design method for cosine-modulated filter banks using window functions

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SIGNAL PROCESSING 2007年第5期87卷 811-823页

作者： Bergen, Stuart W. A. Antoniou, Andreas Univ Victoria Dept Elect & Comp Engn Victoria BC V8W 3P6 Canada

An efficient closed-form method for designing M-channel cosine-modulated filter banks with prescribed stopband attenuation and channel overlap is proposed. The method employs the window technique for the prototype filter design and is based on empirical formulas that give the filter length and the window parameters that would satisfy the prescribed specifications. When compared with iterative methods, the proposed method significantly reduces the computational cost associated with the design making it a suitable candidate for applications where the design must be carried out in real or quasi-real time. Applications of the proposed method in the area of subband processing of speech, audio, and ECG signals are considered. (c) 2006 Elsevier B.V. All rights reserved.

关键词： cosine-modulated filter banks nonrecursive (FIR) filter design window functions

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Mappings of window functions 33

Mappings of Window Functions

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33rd Annual IEEE Military Communications Conference on Affordable Mission Success - Meeting the Challenge (MILCOM)

作者： Fritz, Christopher Fam, Adly T. SUNY Buffalo Dept EE Buffalo NY 14260 USA

ISBN: (纸本)9781479967704

In this paper we examine the mathematical relationships between window functions that share the same finite support. First, we find that the set of windows is closed under mappings that transform one into another or operations that operate on two or more windows that produce another window in the set. These operations include linear combinations, geometric combinations, raising to a power, and others, which all result in new window functions. The linear combination mapping operates on a number of windows to produce a new window in their convex hull and results in a search space using the Barycentric coordinates of any point to find optimal windows to satisfy a cost function. Any sequence of transformations or operations will result in fixed points. These fixed points, which are invariant under the operations, reflect the limits and importance of the operations. Operating on given windows with a sequence of transformations and operations, possibly iteratively, is shown to result in optimal windows.

关键词： window functions Transformations and Operations Fixed points Sidelobes Mainlobe

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Effect of window functions on the Sequential Bayesian Filtering Based Frequency Estimation 21

Effect of Window Functions on the Sequential Bayesian Filter...

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21st International Symposium on Wireless Personal Multimedia Communications (WPMC)

作者： Aunsri, Nattapol Mae Fah Luang Univ Brain Sci & Engn Innovat Res Grp Sch Informat Technol Chiang Rai 57100 Thailand

ISBN: (纸本)9781538657577

window functions are typically used in time-frequency (TF) signal analysis, especially in spectrogram calculation. In frequency estimation problems, most methods for solving such tasks rely on the spectrogram-based approach where the time-series of the signal is considered in the frequency domain via the short-time Fourier transform (STFT). Sequential Bayesian filtering has been one of the most powerful methods for sequential estimation of time-varying parameters where the signal model and observation data are complicated in terms of nonliear/non-Gaussian assumptions. The method integrates mathematical and statistical properties of the signal in order to construct a posterior probability density functions of the interesting parameters. Therefore, when window function is applied in STFT, the statistical property of the transformed domain may be destroy, resulting in the movement of the frequency estimates according to the window type used in spectrogram calculation. Therefore, we investigate in this work the effect of windows on the accuracy of the sequential Bayesian filtering based frequency estimation. Simulation results show that window has some effect only when the noise level is high.

关键词： window functions spectrogram frequency estimation particle filter sequential B ayesian filtering signal processing

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Reducing Data Transfer in Parallel Processing of SQL window functions 6

Reducing Data Transfer in Parallel Processing of SQL Window ...

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6th International Conference on Cloud Computing and Services Science (CLOSER)

作者： Coelho, Fabio Pereira, Jose Vilaca, Ricardo Oliveira, Rui INESC TEC Braga Portugal Univ Minho Braga Portugal

ISBN: (纸本)9789897581823

window functions are a sub-class of analytical operators that allow data to be handled in a derived view of a given relation, while taking into account their neighboring tuples. We propose a technique that can be used in the parallel execution of this operator when data is naturally partitioned. The proposed method benefits the cases where the required partitioning is not the natural partitioning employed. Preliminary evaluation shows that we are able to limit data transfer among parallel workers to 14% of the registered transfer when using a naive approach.

关键词： window functions Reactive Programming Parallel Systems OLAP SQL

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