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A new fast-lock, low-jitter, and all-digital frequency synthesizer for DVB-T receivers

INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS 2015年第5期43卷 566-578页

作者： Gholami, Mohammad Rahimpour, Hamid Ardeshir, Gholamreza Miar-Naimi, Hossein Babol Noshirvani Univ Technol Babol Sar Iran

Lock time and convergence time are the most important challenges in delay-locked loops (DLLs). In this paper we cover French very high frequency band with a novel all-digital fast-lock DLL-based frequency synthesizer. Because this new architecture uses a digital signal processing unit instead of using phase frequency detector, charge pump, and loop filter in conventional DLL, therefore, it shows better jitter performance, lock time, and convergence speed than previous related works. Optimization methods are used to make input and output signals of the proposed DLL in phase. The proposed architecture is designed to cover all channels of French very high frequency band by choosing number of delay cells in signal path. Simulation has been done for 22-27 delay cells, and f(REF)=16MHz, which can produce output frequency in range of 176-216MHz. Locking time is approximately 0.3 mu s, which is equal to five clock cycles of reference clock. All of the simulation results show superiority of the proposed structure. Copyright (c) 2013 John Wiley & Sons, Ltd.

关键词： delay locked loop (DLL) conjugate gradient algorithm optimization synthesizer

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Averaging complex subspaces via a Karcher mean approach

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SIGNAL PROCESSING 2013年第2期93卷 459-467页

作者： Hueper, K. Kleinsteuber, M. Shen, H. Tech Univ Munich Dept Elect Engn & Informat Technol D-80333 Munich Germany Univ Wurzburg Dept Math D-97074 Wurzburg Germany

We propose a conjugate gradient type optimization technique for the computation of the Karcher mean on the set of complex linear subspaces of fixed dimension, modeled by the so-called Grassmannian. The identification of the Grassmannian with Hermitian projection matrices allows an accessible introduction of the geometric concepts required for an intrinsic conjugate gradient method. In particular, proper definitions of geodesics, parallel transport, and the Riemannian gradient of the Karcher mean function are presented. We provide an efficient step-size selection for the special case of one dimensional complex subspaces and illustrate how the method can be employed for blind identification via numerical experiments. (C) 2012 Elsevier B.V. All rights reserved.

关键词： conjugate gradient algorithm Grassmannian Complex projective space Complex linear subspaces Karcher mean

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Scattered data approximation by regular grid weighted smoothing

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SADHANA-ACADEMY PROCEEDINGS IN ENGINEERING SCIENCES 2018年第1期43卷 1-16页

作者： Francis, Bibin Viswanath, Sanjay Arigovindan, Muthuvel Indian Inst Sci Dept Elect Engn ISL Bangalore 560012 Karnataka India

Scattered data approximation refers to the computation of a multi-dimensional function from measurements obtained from scattered spatial locations. For this problem, the class of methods that adopt a roughness minimization are the best performing ones. These methods are called variational methods and they are capable of handling contrasting levels of sample density. These methods express the required solution as a continuous model containing a weighted sum of thin-plate spline or radial basis functions with centres aligned to the measurement locations, and the weights are specified by a linear system of equations. The main hurdle in this type of method is that the linear system is ill-conditioned. Further, getting the weights that are parameters of the continuous model representing the solution is only a part of the effort. Getting a regular grid image requires re-sampling of the continuous model, which is typically expensive. We develop a computationally efficient and numerically stable method based on roughness minimization. The method leads to an algorithm that uses standard regular grid array operations only, which makes it attractive for parallelization. We demonstrate experimentally that we get these computational advantages only with a little compromise in performance when compared with thin-plate spline methods.

关键词： Scattered data approximation variational reconstruction conjugate gradient algorithm multi-resolution approach thin-plate splines radial basis functions

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A new experimental device and inverse method to characterize thermal properties of composite phase change materials

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COMPOSITE STRUCTURES 2015年第Dec.期133卷 1149-1159页

作者： Didier, Gossard Mustapha, Karkri Mariam, AlMaadeed A. Igor, Krupa Univ Paris Est CERTES F-94010 Creteil France Qatar Univ Ctr Adv Mat Doha 2713 Qatar

A new experimental device has been developed in order to characterize the phase change material (PCM) thermal properties (thermal conductivity k, sensible and latent heat thermal energy storage, c(p) and L-f) in the solid phase, during the solid-liquid transition and in the liquid phase. It allows to measure cylindrical samples of maximum 60 mm radius and 10 mm thick. A typical measurement consists in imposing a vertical temperature gradient through the PCM sample driven by a heat source, monitoring during the experiment time all the boundary conditions (temperatures and heat fluxes) and measuring temperature evolution in three locations within the PCM sample. In this work, we will focus only on the solid thermal conductivity characterization. These experiment data are used to solve the inverse heat conduction problem by applying the conjugate gradient method and finally, to determine the PCM thermal properties. Two types of composite PCM have been thermally characterized: paraffin mixed with synthetic graphite (Timrex SFG75) and paraffin mixed with graphite waste. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Composite PCMs (phase change materials) Thermal conductivity Sensible heat Latent heat Inverse problem conjugate gradient algorithm

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Enhancing k-Space Quantitative Susceptibility Mapping by Enforcing Consistency on the Cone Data (CCD) with Structural Priors

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MAGNETIC RESONANCE IN MEDICINE 2016年第2期75卷 823-830页

作者： Wen, Yan Wang, Yi Liu, Tian MedImageMetric LLC New York NY USA Cornell Univ Dept Biomed Engn Ithaca NY USA Cornell Univ Dept Radiol Weill Med Coll New York NY USA

Purpose: The inversion from the magnetic field to the magnetic susceptibility distribution is ill-posed because the dipole kernel, which relates the magnetic susceptibility to the magnetic field, has zeroes at a pair of cone surfaces in the k-space, leading to streaking artifacts on the reconstructed quantitative susceptibility maps (QSM). A method to impose consistency on the cone data (CCD) with structural priors is proposed to improve the solutions of k-space methods. Methods: The information in the cone region is recovered by enforcing structural consistency with structural prior, while information in the noncone trust region is enforced to be consistent with the magnetic field measurements in k-space. This CCD method was evaluated by comparing the initial results of existing QSM algorithms to the QSM results after CCD enhancement with respect to the COSMOS results in simulation, phantom, and in vivo human brain. Results: The proposed method demonstrated suppression of streaking artifacts and the resulting QSM showed better agreement with reference standard QSM compared with other k-space based methods. Conclusion: By enforcing consistency with structural priors in the cone region, the missing data in the cone can be recovered and the streaking artifacts in QSM can be suppressed. (C) 2015 Wiley Periodicals, Inc. Key words: quantitative susceptibility mapping;conjugate

关键词： quantitative susceptibility mapping conjugate gradient algorithm data fitting

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SHAPING OF SYSTEM RESPONSES WITH MINIMAX OPTIMIZATION IN THE TIME DOMAIN

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1993年第1期16卷 40-46页

作者： OHTSUKA, T FUJII, H Tokyo Metropolitan Institute of Technology Tokyo 191 Japan

A minimax problem is introduced for the terminal control of a generic dynamical system without disturbances. The maximum magnitude of the weighted output of the system is minimized over a finite interval by the control input of a prescribed class. Such important characteristics of the controlled system appear explicitly in the proposed problem as the maximum magnitude and settling property of the output. Two numerical examples are shown to illustrate the problem. A slewing experiment is also presented to demonstrate the application of the minimax optimal control.

关键词： Transversality Condition Control System Design Terminal Control Distributed Parameter System Bernoulli Euler Beams Vibration Suppression Feedback Control System Large Angle Maneuver Mathematical Models conjugate gradient algorithm

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Identifying a diffusion coefficient in a time-fractional diffusion equation

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MATHEMATICS AND COMPUTERS IN SIMULATION 2018年 151卷 77-95页

作者： Wei, T. Li, Y. S. Lanzhou Univ Sch Math & Stat Lanzhou 730000 Gansu Peoples R China GanSu Polit Sci & Law Inst Sch Cyber Secur Lanzhou 730000 Gansu Peoples R China

In this paper, we propose a conjugate gradient algorithm for identifying a space-dependent diffusion coefficient in a time-fractional diffusion equation from the boundary Cauchy data in one-dimensional case. The existence and uniqueness of the solution for a weak form of the direct problem are obtained. The identification of diffusion coefficient is formulated into a variational problem by the Tikhonov-type regularization. The existence, stability and convergence of a minimizer for the variational problem approach to the exact diffusion coefficient are provided. We use a conjugate gradient method to solve the variational problem based on the deductions of a sensitive problem and an adjoint problem. We test three numerical examples and show the effectiveness of the proposed method. (C) 2018 International Association for Mathematics and Computers in Simulation (IMACS). Published by Elsevier B.V. All rights reserved.

关键词： Inverse diffusion coefficient problem Fractional diffusion equation conjugate gradient algorithm

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COMPARISON OF STANDARD AND MATRIX-FREE IMPLEMENTATIONS OF SEVERAL NEWTON-KRYLOV SOLVERS

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AIAA JOURNAL 1994年第12期32卷 2394-2400页

作者： MCHUGH, PR KNOLL, DA LOCKHEED IDAHO TECHNOL CO IDAHO NATL ENGN UBDEPT ENGN ANALIDAHO FALLSID 83415

Fully coupled Newton's method is combined with conjugate gradient-like iterative algorithms to form inexact Newton-Krylov algorithms for solving the steady, incompressible, Navier-Stokes and energy equations in primitive variables. Finite volume differencing is employed using the power law convection-diffusion scheme on a uniform but staggered mesh. The well-known model problem of natural convection in an enclosed cavity is solved. Three conjugate gradient-like algorithms are selected from a class of algorithms based upon the Lanczos biorthogonalization procedure;namely, the conjugate gradients squared algorithm, the transpose-free quasi-minimal-residual algorithm, and a more smoothly convergent version of the biconjugate gradients algorithm. A fourth algorithm is based upon the Arnoldi process, namely the popular generalized minimal residual algorithm (GMRES). The performance of a standard inexact Newton's method implementation is compared with a matrix-free implementation. Results indicate that the performance of the matrix-free implementation is strongly dependent upon grid size (number of unknowns) and the selection of the conjugate gradient-like method. GMRES appeared to be superior to the Lanczos based algorithms within the context of a matrix-free implementation.

关键词： Newton's Method conjugate gradient algorithm Natural Convection conjugate gradient Method Continuity Equation Buoyancy Force Boussinesq Approximation Finite Difference Approximation Navier Stokes Equations Characteristic Velocity

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Uniformizing field distribution along optical axis for volume holographic data storage

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OPTICS COMMUNICATIONS 2001年第1-2期192卷 19-26页

作者： Yang, JW Wang, MR Univ Miami Dept Elect & Comp Engn Coral Gables FL 33124 USA

The conjugate gradient method is adopted to design one phase mask for each stored pattern to improve the uniformity of transverse and axial field distributions in recording medium volume for holographic data storage system. Simulation results demonstrate that almost constant field amplitude of the object beam can be obtained in the medium volume. The reconstruction error is found to be the lowest compared to that of using other types of masks or no masks. Using the phase mask allows effective use of the medium volume and its dynamic range and improves reconstruction performances of stored holograms. (C) 2001 Elsevier Science B.V. All rights reserved.

关键词： optical holographic data storage phase mask conjugate gradient algorithm

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Fast robust quasi-Newton algorithm for adaptive arrays

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IEE PROCEEDINGS-COMMUNICATIONS 1999年第4期146卷 231-239页

作者： Klemes, M Nortel Networks Dept R412 Microwave Radio Syst Dev Ottawa ON K1Y 4H7 Canada

A stable, fast (order-of-N) quasi-Newton (QN) algorithm (FRQN) applicable to arbitrary at-ray signals is presented. Its complexity is only twice that of the normalised least mean squares (NLMS) algorithm, yet its convergence is faster and smoother, proceeding along the optimal QN path as that of the order N-2 recursive least squares (RLS) algorithm, albeit more slowly. The development of its recursive update equation is outlined and compared to those of the NLMS and RLS algorithms, as well as variations of the conjugate gradient (CG) algorithm. Analytic expressions for its excess mean squared error in stationary and non-stationary scenarios are presented and compared with those of the LMS algorithm. Simulations of an adaptive array in a mobile wireless base-station show that the FRQN performance falls between that of the NLMS and RLS algorithms for a wide range of signal scenarios.

关键词： mean square error methods stable quasi-Newton algorithm normalised least mean squares adaptive signal processing computational complexity Antenna arrays radiofrequency interference mean squared error mobile wireless base-station array signals Signal processing and detection convergence recursive least squares algorithm recursive update equation Mobile radio systems nonstationary signals Electromagnetic compatibility and interference Newton method numerical stability complexity conjugate gradient algorithm NLMS algorithm interference cancellation land mobile radio Interpolation and function approximation (numerical analysis) adaptive antenna arrays digital adaptive array algorithm stationary signals fast robust quasi-Newton algorithm RLS algorithm interference suppression

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