HKU Scholars Hubhttp://hub.hku.hkThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Tue, 18 May 2021 00:00:13 GMT2021-05-18T00:00:13Z502001- Signal processing: linearized noise analysis of delta-operator based filters and nonlinear stability study ofsigma-delta modulatorshttp://hdl.handle.net/10722/35806Title: Signal processing: linearized noise analysis of delta-operator based filters and nonlinear stability study ofsigma-delta modulators
Authors: Wong, Ngai; 黃毅
Tue, 01 Jan 2002 00:00:00 GMThttp://hdl.handle.net/10722/358062002-01-01T00:00:00Z
- VLSI Implementation of Multiplierless Filtershttp://hdl.handle.net/10722/99311Title: VLSI Implementation of Multiplierless Filters
Authors: Lei, CU; Wong, N
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/10722/993112006-01-01T00:00:00Z
- Efficient complex continuous-time IIR filter design via generalized vector fittinghttp://hdl.handle.net/10722/99495Title: Efficient complex continuous-time IIR filter design via generalized vector fitting
Authors: Lei, CU; Cheung, CM; Kwan, HK; Wong, N
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/10722/994952008-01-01T00:00:00Z
- Efficient linear macromodeling via discrete-time time-domain vector fittinghttp://hdl.handle.net/10722/98795Title: Efficient linear macromodeling via discrete-time time-domain vector fitting
Authors: Lei, CU; Wong, N
Abstract: We present a discrete-time time-domain vector fitting algorithm, called TD-VFz, for rational function macromodeling of port-to-port responses with discrete time-sampled data. The core routine involves a two-step pole refinement process based on a linear least-squares solve and an eigen-value problem. Applications in the macromodeling of practical circuits demonstrate that TD-VFz exhibits fast computation, excellent accuracy, and robustness against noisy data. We also utilize an quasi-error bound unique to the discrete-time setting to facilitate the determination of approximant model order. © 2008 IEEE.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/10722/987952008-01-01T00:00:00Z
- Direct Finite-Element-Based Solver for 3D-IC Thermal Analysis via H-Matrix Representationhttp://hdl.handle.net/10722/204034Title: Direct Finite-Element-Based Solver for 3D-IC Thermal Analysis via H-Matrix Representation
Authors: Li, YC; Tan, S; Yu, T; Huang, X; Wong, N
Abstract: We propose, for the first time, the use of hierarchical matrix ($mathcal{H}$-matrix) in the efficient finite-element-based (FE-based) direct solver implementation for both steady and transient thermal analyses of three-dimensional integrated circuits (3D ICs). $mathcal{H}$-matrix was shown to provide a data-sparse way to approximate the matrices and their inverses with almost linear space and time complexities. We show this is also true for FE-based transient analysis of thermal parabolic partial differential equations (PDEs). Specifically, we show that the stiffness matrix from a FE-based steady and transient thermal analysis can be represented by $mathcal{H}$-matrix without approximation, and its inverse and Cholesky factors can be evaluated by $mathcal{H}$-matrix with controlled accuracy. We then show that the memory and time complexities of the solver are bounded by $mathcal{O}(mathit{k_1N}log{N})$ and $mathcal{O}(mathit{k_1^2N}log^2N)$, respectively, for very large scale thermal systems, where $k_1$ is a small quantity determined by accuracy requirements and $mathit{N}$ is the number of unknowns in the system. Numerical results demonstrate that the proposed method shows significant advantages over the LU based analysis techniques in terms of both memory and time complexity.
Description: Conference Theme: Security in a Connected World; Poster Session & Mixer
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10722/2040342014-01-01T00:00:00Z
- A common subexpression sharing approach for multiplierless synthesis of multiple constant multiplicationshttp://hdl.handle.net/10722/198890Title: A common subexpression sharing approach for multiplierless synthesis of multiple constant multiplications
Authors: Ho, Yuen Hong Alvin; Lei, Chi-Un; Wong, Ngai
Abstract: In the context of multiple constant multiplication (MCM) filter design, we propose a search space that combines the shifted sum/difference of coefficients as well as minimal signed digit (MSD) representation. The search space further reduces the number of adders/subtractors in the synthesis of MCM from MSD representation. A novel common subexpression elimination (CSE) algorithm is adapted to the proposed search space. Our synthesized multiplierless filters are benchmarked against representative examples and found to achieve hardware reduction in most cases.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10722/1988902007-01-01T00:00:00Z
- Novel 2D linear-phase IIR filter design and application in noise removalhttp://hdl.handle.net/10722/198891Title: Novel 2D linear-phase IIR filter design and application in noise removal
Authors: Cheung, Chungman; Lei, Chi-Un; Wong, Ngai
Abstract: We present an efficient and novel procedure to design two-dimensional (2D) linear-phase IIR filters with less hardware resource. A 2D linear-phase FIR filter prototype is first designed using semidefinite programming (SDP). The prototype filter is then decomposed into modular structures via Schur decomposition method (SDM). Each section is reduced into IIR structures using a novel digital system identification technique called the Discrete-Time Vector Fitting (VFz). Examples with image processing application shows the algorithm exhibits fast convergence and produces low hardware cost and accurate filters.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10722/1988912007-01-01T00:00:00Z
- Novel 2D linear-phase IIR filter design and application in noise removalhttp://hdl.handle.net/10722/99758Title: Novel 2D linear-phase IIR filter design and application in noise removal
Authors: Cheung, CM; Lei, CU; Wong, N
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10722/997582007-01-01T00:00:00Z
- DC stability analysis of high-order, lowpass ΣΔ modulators with distinct unit circle NTF zeroshttp://hdl.handle.net/10722/42955Title: DC stability analysis of high-order, lowpass ΣΔ modulators with distinct unit circle NTF zeros
Authors: Wong, N; Ng, TS
Abstract: This paper presents an analytical approach to the investigation of the dc stability of high-order (order > 2), low-pass (LP) ΣΔ modulators with distinct noise transfer function (NTF) zeros on the unit circle. The techniques of state-space diagonalization and decomposition, continuous-time embedding and Poincaré map analysis are combined and extended. It is revealed that high-order ΣΔ modulators can be transformed and decomposed into second- and first-order subsystems. The investigation, coupled with efficient numerical methods, generalizes itself to different types of transition flow and provides theoretical insight into the state trajectory and limit cycle behavior. It is shown that estimation of dc input bounds based solely on the boundary transition flow is inadequate. A procedure utilizing the information from different transition flow assumptions and the discrete nature of a modulator is introduced for locating the stable dc input bounds of practical, discrete-time ΣΔ modulators.
Wed, 01 Jan 2003 00:00:00 GMThttp://hdl.handle.net/10722/429552003-01-01T00:00:00Z
- Time domain equalization for OFDM systemshttp://hdl.handle.net/10722/45904Title: Time domain equalization for OFDM systems
Authors: Shaodan, M; Wong, N; Ng, TS
Abstract: In this paper, a time domain equalization algorithm is proposed for single-TX multiple-RX OFDM systems over frequency selective fading channels. The algorithm, which cancels most of the intersymbol interference (ISI), utilizes the orthogonality of the IFFT matrix and the second order statistics of the received signals. The signals are then detected, with the aid of only four pilots, from the equalizer output. The number of pilots required in the proposed algorithm is less than that in existing algorithms and channel length estimation is not needed. In addition, the proposed algorithm is applicable to both the case where the channel length is shorter than or equal to the length of cyclic prefix (CP), and the case where the channel length is longer than the length of cyclic prefix which results in inter-block interference (IBI). Simulation results confirm the effectiveness of the proposed algorithm in both cases and indicate that it is more practical as there is no restriction on the channel and CP lengths. © 2006 IEEE.
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/10722/459042006-01-01T00:00:00Z
- Efficient linear macromodeling via least-squares response approximationhttp://hdl.handle.net/10722/57274Title: Efficient linear macromodeling via least-squares response approximation
Authors: Lei, CU; Kwan, HK; Liu, Y; Wong, N
Abstract: We present a least-squares (LS) algorithm for rational function macromodeling of port-to-port responses with discrete-time sampled data. The core routine involves over-determined equations and filtering operation, and avoids numerical-sensitive calculation and initial pole assignment. We demonstrate the fast computation and excellent accuracy and robustness, even with noisy data, in stable response approximation. ©2008 IEEE.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/10722/572742008-01-01T00:00:00Z
- Model order reduction for neutral systems by moment matchinghttp://hdl.handle.net/10722/185913Title: Model order reduction for neutral systems by moment matching
Authors: Wang, Q; WANG, Y; Lam, EYM; Wong, N
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10722/1859132013-01-01T00:00:00Z
- A comparison of SAR image speckle filtershttp://hdl.handle.net/10722/158609Title: A comparison of SAR image speckle filters
Authors: Lang, S; Lin, CY; Liu, J; Wong, N; So, HKH
Abstract: High quality images of Earth produced by synthetic aperture radar (SAR) systems have become increasingly available, however, SAR images are difficult to interpret. Speckle reduction remains one of the major issues in SAR imaging process, although speckle has been extensively studied for decades. Many reconstruction filters have been proposed and they can be classified into two categories: multilook and/or minimum mean-square error (MMSE) despeckling using the speckle model; and maximum a posteriori (MAP) or maximum likihood (ML) despeckling using the product model. The most well known Lee, Kuan, and Frost filters belong to first category. These filters are based on conventional techniques that were originally derived for stationary signals, such as MMSE. In the second category, filters are based on the product model, such as the MAP Gaussian filter and the Gamma filter, and require knowledge of the a priori probability density function. These filters force speckle to have nonstationary Gaussian or gamma distributed intensity mean. The speckle filtering is mainly Bayesian model fitting that optimizes the MAP criteria. Scene reconstruction is performed using an inversion of the ascending chain. An objective measure is required to compare the technical merits of these filters, and Shi et al. presented a comparison 15 years ago. In this paper, a brief introduction of speckle, product, and filter models is summarized. A review of some most widely used SAR image speckle filters is given. And stationary speckle filters, like Lee, Kuan, and Frost filters, and nonstationary speckle filters like Gamma MAP filter are studied. Despeckling results on stationary and nonstationary SAR image of these speckle filters are presented. © 2009 Copyright SPIE - The International Society for Optical Engineering.
Thu, 01 Jan 2009 00:00:00 GMThttp://hdl.handle.net/10722/1586092009-01-01T00:00:00Z
- Bit-stream adders and multipliers for tri-level sigma-delta modulatorshttp://hdl.handle.net/10722/57475Title: Bit-stream adders and multipliers for tri-level sigma-delta modulators
Authors: Ng, CW; Wong, N; Ng, TS
Abstract: We propose both adder and multiplier circuits for bit-stream signal processing customized for tri-level sigma-delta modulated signals. These architectures are the 2-bit extensions from the existing 1-bit bit-stream adders and multipliers, and are shown to offer better signal-to-noise performance. Field-programmable gate array implementations then confirm their efficacy. © 2007 IEEE.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10722/574752007-01-01T00:00:00Z
- IIR approximation of FIR filters via discrete-time vector fittinghttp://hdl.handle.net/10722/57444Title: IIR approximation of FIR filters via discrete-time vector fitting
Authors: Wong, N; Lei, CU
Abstract: We present a novel technique for approximating finite-impulse-response (FIR) filters with infinite-impulse-response (IIR) structures through extending the vector fitting (VF) algorithm, used extensively for continuous-time frequency-domain rational approximation, to its discrete-time counterpart called VFz. VFz directly computes the candidate filter poles and iteratively relocates them for progressively better approximation. Each VFz iteration consists of the solutions of an overdetermined linear equation and an eigenvalue problem, with real-domain arithmetic to accommodate complex poles. Pole flipping and maximum pole radius constraint guarantee stability and robustness against finite-precision implementation. Comparison against existing algorithms confirms that VFz generally exhibits fast convergence and produces highly accurate IIR approximants. © 2008 IEEE.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/10722/574442008-01-01T00:00:00Z
- Quad-level bit-stream signal processing on FPGAshttp://hdl.handle.net/10722/61960Title: Quad-level bit-stream signal processing on FPGAs
Authors: Ng, CW; Wong, N; So, HKH; Ng, TS
Abstract: Quad-level bit-stream signal processing (BSSP) circuits are implemented and their performances are compared with previously published tri-level and bi-level BSSP implementations on FPGAs. BSSP refers to the process of performing computation directly on over-sampled delta-sigma modulated signals to eliminate the need of resource consuming decimators and interpolators. Quad-level BSSP offers better performance than their bi-and tri-level counterparts at the expense of higher resource utilization. Using a digital phase locked loop (DPLL) and a quadrature phase-shift keying (QPSK) demodulator as application examples, the effectiveness of quad-level BSSP on FPGAs is studied. The BSSP approach will be contrasted with conventional multi-bit implementations using built-in digital signal processing blocks in modern FPGAs. © 2008 IEEE.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/10722/619602008-01-01T00:00:00Z
- The impact of dispersion fluctuation on the optimization of parametric wavelength exchangehttp://hdl.handle.net/10722/99294Title: The impact of dispersion fluctuation on the optimization of parametric wavelength exchange
Authors: Shen, M; Xu, X; Wong, N; Yuk, TI; Wong, KKY
Abstract: The optimized parameters of wavelength exchange vary from fiber to fiber due to zero-dispersion wavelength fluctuation. This problem can be solved by reducing wavelength separation between signal and idler at the expense of reduced tunability. © 2009 IEEE.
Thu, 01 Jan 2009 00:00:00 GMThttp://hdl.handle.net/10722/992942009-01-01T00:00:00Z
- Limit cycle identification in nonlinear polynomial systemshttp://hdl.handle.net/10722/202842Title: Limit cycle identification in nonlinear polynomial systems
Authors: ZHANG, S; LIU, H; Batselier, K; Wong, N
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10722/2028422013-01-01T00:00:00Z
- Fiber-coupled Emissive Micro-LED Arrayshttp://hdl.handle.net/10722/61923Title: Fiber-coupled Emissive Micro-LED Arrays
Authors: Zhu, L; Ng, CW; Wong, N; Wong, KKY; Lai, PT; Choi, HW
Thu, 01 Jan 2009 00:00:00 GMThttp://hdl.handle.net/10722/619232009-01-01T00:00:00Z
- Robust binary image deconvolution with positive semidefinite programminghttp://hdl.handle.net/10722/118365Title: Robust binary image deconvolution with positive semidefinite programming
Authors: Shen, Y; Lam, EYM; Wong, N
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/10722/1183652006-01-01T00:00:00Z
- An efficient stochastic integral equation method for modeling the influence of conductor surface roughness on interconnect ohmic losshttp://hdl.handle.net/10722/99308Title: An efficient stochastic integral equation method for modeling the influence of conductor surface roughness on interconnect ohmic loss
Authors: Chen, Q; Wong, N
Abstract: Due to the shrinking skin depth in high-frequency analog and digital circuits, surface roughness now has a significant impact on interconnect ohmic loss, which tends to be ignored in conventional EDA tools. An effective conductivity (EC) has been proposed as the metric of this impact, but the large amount of computation resulted from the Monte-Carlo (MC) simulation prohibits practical use. In this paper, we propose a computationally efficient stochastic integral equation (SIE) method to statistically compute the EC as an alternative to the timeconsuming MC simulation. An effective second-order correction utilizing model order reduction (MOR) techniques is developed to substantially improve the accuracy at an acceptable cost. Numerical experiments then verify the efficacy of the proposed method. ©2007 IEEE.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10722/993082007-01-01T00:00:00Z
- Investigation of random rough surface effects in interconnect resistance extraction utilizing effective conductivityhttp://hdl.handle.net/10722/99802Title: Investigation of random rough surface effects in interconnect resistance extraction utilizing effective conductivity
Authors: Chen, Q; Wong, N
Abstract: Due to the decreasing skin depth in high-frequency analog and digital circuits, surface roughness is playing an increasingly important role in interconnect parasitic extraction. However, the inaccessibility of explicit surface expression and the complicated electromagnetic (EM) nature baffle the satisfactory solution to this kind of problems. In this paper, the impact of random surface roughness on the frequency-dependent resistance extraction for interconnects is quantitively evaluated by the concept of effective conductivity. The surface information is given in terms of statistical description instead of explicit functions. We combine the equivalent source method with the Monte Carlo simulation, called generalized equivalent source method (GESM), to analyze the behavior of EM wave on random rough surfaces. These techniques simplify the investigation of rough surface effects in interconnect parasitic extractions and full-wave analyses for signal integrity. © 2006 IEEE.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10722/998022007-01-01T00:00:00Z
- Systematic power minimization in multibit delta-sigma analog-to-digital convertershttp://hdl.handle.net/10722/99742Title: Systematic power minimization in multibit delta-sigma analog-to-digital converters
Authors: Lui, SH; Wong, N
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/10722/997422006-01-01T00:00:00Z
- Binary image deconvolution with positive semidefinite programminghttp://hdl.handle.net/10722/99743Title: Binary image deconvolution with positive semidefinite programming
Authors: Shen, Y; Lam, EYM; Wong, N
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/10722/997432006-01-01T00:00:00Z
- A stochastic integral equation method for resistance extraction of conductors with random rough surfaceshttp://hdl.handle.net/10722/99675Title: A stochastic integral equation method for resistance extraction of conductors with random rough surfaces
Authors: Chen, Q; Wong, N
Abstract: Due to the decreasing skin depth in high-frequency analog and digital circuits, surface roughness is playing an increasingly important role in interconnect parasitic extraction. However, the inaccessibility of detailed surface description and the complicated electromagnetic (EM) nature baffle satisfactory solutions to this kind of problems. In this paper, a new stochastic integral equation method is proposed to quantitively evaluate the impact of surface roughness on the frequency-dependent resistance extraction for interconnects. The surface information is given by statistical description instead of explicit functions. The direct derivation of the expected value of the surface integral equation of the EM wave eliminates the need of time-consuming Monte Carlo simulations. Numerical results verify the accuracy of the proposed method. © 2006 IEEE.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10722/996752007-01-01T00:00:00Z
- Magnetic coupling calculations using partial inductance theoryhttp://hdl.handle.net/10722/158689Title: Magnetic coupling calculations using partial inductance theory
Authors: Zhan, Y; Fong, NHW; Choi, AHW; Wong, N
Abstract: Quantitative analysis of magnetic coupling problems involves the calculations of self inductance of conductors, mutual inductance between conductors, and inductive coupling coefficient etc. It is an issue of great interest along the whole electromagnetics evolvement history. Formerly, the calculations have to be carried out with the aid of three-dimentional EDA solvers by discretization of the entire volume. This is rather tedious and computationally expensive. Engineers may need a simple approach to estimate the inductance values without any complex computational tools. In this paper, we propose a new method to fulfill this task based on partial inductance theory. An example with the procedure to calculate coupling coefficient of two magnetic resonant coils is presented. © 2010 IEEE.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10722/1586892010-01-01T00:00:00Z
- On Vector Fitting methods in signal/power integrity applicationshttp://hdl.handle.net/10722/129644Title: On Vector Fitting methods in signal/power integrity applications
Authors: Lei, CU; Wang, Y; Chen, Q; Wong, N
Abstract: Vector Fitting (VF) has been applied to reformulate traditional system identification techniques by introducing a partial-fraction basis to avoid ill-conditioned calculation in broadband system identifications. Because of the reliable and versatility of VF, many extensions and applications have been proposed, for example, the macromodeling of linear structures in signal/power integrity analyses. In this paper, we discuss the macromodeling framework and some main features in VF in terms of data, algorithms and models. Finally, an alternative P-norm approximation criterion is proposed to enhance the macromodeling process.
Description: This conference proceedings appears in: Lecture Notes in Engineering and Computer Science. Open-access online version: http://www.iaeng.org/publication/IMECS2010/
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10722/1296442010-01-01T00:00:00Z
- VISA: Versatile impulse structure approximation for time-domain linear macromodelinghttp://hdl.handle.net/10722/129647Title: VISA: Versatile impulse structure approximation for time-domain linear macromodeling
Authors: Lei, CU; Wong, N
Abstract: We develop a rational function macromodeling algorithm named VISA (Versatile Impulse Structure Approximation) for macromodeling of system responses with (discrete) time-sampled data. The ideas of Walsh theorem and complementary signal are introduced to convert the macromodeling problem into a non-pole-based Steiglitz-McBride (SM) iteration (a class of first- and second-order interpolations) without initial guess and eigenvalue computation. We demonstrate the fast convergence and the versatile macromodeling requirement adoption through a P-norm approximation expansion, using examples from practical data.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10722/1296472010-01-01T00:00:00Z
- An extension of the generalized Hamiltonian method to S-parameter descriptor systemshttp://hdl.handle.net/10722/129657Title: An extension of the generalized Hamiltonian method to S-parameter descriptor systems
Authors: Zhang, Z; Wong, N
Abstract: A generalized Hamiltonian method (GHM) was recently proposed for the passivity test of hybrid descriptor systems [1]. This paper extends the GHM theory to its S-parameter counterpart. Based on the S-parameter GHM, a passivity test flow is proposed, which is capable of detecting nonpassive regions of descriptor-form physical models. The proposed method is applicable to S-parameter and hybrid systems either in the standard state-space or descriptor forms. Experimental results confirm the effectiveness and accuracy of the proposed method.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10722/1296572010-01-01T00:00:00Z
- Passivity check of S-Parameter descriptor systems via S-Parameter generalized hamiltonian methodshttp://hdl.handle.net/10722/139230Title: Passivity check of S-Parameter descriptor systems via S-Parameter generalized hamiltonian methods
Authors: Zhang, Z; Wong, N
Abstract: This paper extends the generalized Hamiltonian method (GHM) (Zhang , 2009; Zhang and Wong, 2010) and its half-size variant (HGHM) (Zhang and Wong, 2010) to their S-parameter counterparts (called S-GHM and S-HGHM, respectively), for testing the passivity of S-parameter descriptor-form models widely used in high-speed circuit and electromagnetic simulations. The proposed methods are capable of accurately detecting the possible nonpassive regions of descriptor-form models with either scattering or hybrid (impedance or admittance) transfer matrices. Their effectiveness and accuracy are verified with several practical examples. The S-GHM and S-HGHM methods presented here provide a foundation for the passivity enforcement of $S$- parameter descriptor systems. © 2006 IEEE.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10722/1392302010-01-01T00:00:00Z
- Automatic system architecture synthesis for FPGA-based reconfigurable computershttp://hdl.handle.net/10722/129739Title: Automatic system architecture synthesis for FPGA-based reconfigurable computers
Authors: Lin, CY; Wong, N; So, HKH
Abstract: The goal of this PhD project is to develop an automatic method of system architecture synthesis for general high-performance applications on FPGA-based reconfigurable computers. Through our previous research, we have built a theoretical model targeting the scheduling problem with first-order hardware constraints. And a list scheduling algorithm is developed to achieve near-optimal performances. Currently, we are working on the low-level implementation. A systolic architecture is used, and the list scheduling algorithm will be extended to take into account constraints deriving from exact hardware architecture. (Abstract by, IEEE)
Description: In Proceedings of the IEEE International Conference on FieId-Programmable Technology, 2009, p. 475-476
Thu, 01 Jan 2009 00:00:00 GMThttp://hdl.handle.net/10722/1297392009-01-01T00:00:00Z
- A sub-1 V, 26 μw, low-output-impedance CMOS bandgap reference with a low dropout or source follower modehttp://hdl.handle.net/10722/139229Title: A sub-1 V, 26 μw, low-output-impedance CMOS bandgap reference with a low dropout or source follower mode
Authors: Ng, DCW; Kwong, DKK; Wong, N
Abstract: We present a low-power bandgap reference (BGR), functional from sub-1 V to 5 V supply voltage with either a low dropout (LDO) regulator or source follower (SF) output stage, denoted as the LDO or SF mode, in a 0.5-μm standard digital CMOS process with V tn≈ 0.6 V and |V tp| ≈ 0.7 V at 27 °C. Both modes operate at sub-1 V under zero load with a power consumption of around 26 μW. At 1 V (1.1 V) supply, the LDO (SF) mode provides an output current up to 1.1 mA (0.35 mA), a load regulation of ±8.5 mV/mA (±33 mV/mA) with approximately 10 μ s transient, a line regulation of ±4.2 mV/V (±50μV/V), and a temperature compensated reference voltage of 0.228 V (0.235 V) with a temperature coefficient around 34 ppm/° C from -20°C to 120 °C. At 1.5 V supply, the LDO (SF) mode can further drive up to 9.6 mA (3.2 mA) before the reference voltage falls to 90% of its nominal value. Such low-supply-voltage and high-current-driving BGR in standard digital CMOS processes is highly useful in portable and switching applications. © 2010 IEEE.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/10722/1392292011-01-01T00:00:00Z
- An efficient projector-based passivity test for descriptor systemshttp://hdl.handle.net/10722/129215Title: An efficient projector-based passivity test for descriptor systems
Authors: Zhang, Z; Wong, N
Abstract: An efficient passivity test based on canonical projector techniques is proposed for descriptor systems (DSs) widely encountered in circuit and system modeling. The test features a natural flow that first evaluates the index of a DS, followed by possible decoupling into its proper and improper subsystems. Explicit state-space formulations for respective subsystems are derived to facilitate further processing such as model order reduction and/or passivity enforcement. Efficient projector construction and a fast generalized Hamiltonian test for the proper-part passivity are also elaborated. Numerical examples then confirm the superiority of the proposed method over existing passivity tests for DSs based on linear matrix inequalities or skew-Hamiltonian/Hamiltonian matrix pencils. © 2010 IEEE.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10722/1292152010-01-01T00:00:00Z
- Efficient positive-real balanced truncation of symmetric systems via cross-riccati equationshttp://hdl.handle.net/10722/57468Title: Efficient positive-real balanced truncation of symmetric systems via cross-riccati equations
Authors: Wong, N
Abstract: We present a highly efficient approach for realizing a positive-real balanced truncation (PRBT) of symmetric systems. The solution of a pair of dual algebraic Riccati equations in conventional PRBT, whose cost constrains practical large-scale deployment, is reduced to the solution of one cross-Riccati equation (XRE). The cross-Riccatian nature of the solution then allows a simple construction of PRBT projection matrices, using a Schur decomposition, without actual balancing. An invariant subspace method and a modified quadratic alternating-direction-implicit iteration scheme are proposed to efficiently solve the XRE. A low-rank variant of the latter is shown to offer a remarkably fast PRBT speed over the conventional implementations. The XRE-based framework can be applied to a large class of linear passive networks, and its effectiveness is demonstrated through numerical examples. © 2008 IEEE.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/10722/574682008-01-01T00:00:00Z
- Passivity test of immittance descriptor systems based on generalized hamiltonian methodshttp://hdl.handle.net/10722/129226Title: Passivity test of immittance descriptor systems based on generalized hamiltonian methods
Authors: Zhang, Z; Wong, N
Abstract: A generalized Hamiltonian method (GHM) and its half-size variant (HGHM) are proposed to characterize the spectral behaviors of descriptor systems (DSs). With the preprocess improper part test, GHM and HGHM can be applied to test the passivity of immittance (impedance or admittance) DSs without system decomposition, system index assumption, or minimal realization requirement, which are the major bottlenecks of existing algebraic DS passivity tests. The proposed method allows exact detection of nonpassive frequency intervals, which is not possible with frequency-sweeping techniques. Numerical results confirm the effectiveness of the proposed methods. © 2006 IEEE.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10722/1292262010-01-01T00:00:00Z
- A novel linear algebra method for the determination of periodic steady states of nonlinear oscillatorshttp://hdl.handle.net/10722/216391Title: A novel linear algebra method for the determination of periodic steady states of nonlinear oscillators
Authors: Liu, H; Batselier, K; Wong, N
Abstract: Periodic steady-state (PSS) analysis of nonlinear oscillators has always been a challenging task in circuit simulation. We present a new way that uses numerical linear algebra to identify the PSS(s) of nonlinear circuits. The method works for both autonomous and excited systems. Using the harmonic balancing method, the solution of a nonlinear circuit can be represented by a system of multivariate polynomials. Then, a Macaulay matrix based root-finder is used to compute the Fourier series coefficients. The method avoids the difficult initial guess problem of existing numerical approaches. Numerical examples show the accuracy and feasibility over existing methods. © 2014 IEEE.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10722/2163912014-01-01T00:00:00Z
- A fast Newton/Smith algorithm for solving algebraic Riccati equations and its application in model order reductionhttp://hdl.handle.net/10722/45855Title: A fast Newton/Smith algorithm for solving algebraic Riccati equations and its application in model order reduction
Authors: Wong, N; Balakrishnan, V; Koh, CK; Ng, TS
Abstract: A very fast Smith-method-based Newton algorithm is introduced for the solution of large-scale continuous-time algebraic Riccati equations (CAREs). When the CARE contains low-rank matrices, as is common in the modeling of physical systems, the proposed algorithm, called the Newton/Smith CARE or NSCARE algorithm, offers significant computational savings over conventional CARE solvers. Effectiveness of the algorithm is demonstrated in the context of VLSI model order reduction wherein stochastic balanced truncation (SBT) is used to reduce large-scale passive circuits. It is shown that the NSCARE algorithm exhibits guaranteed quadratic convergence under mild assumptions. Moreover, two large-sized matrix factorizations and one large-scale singular value decomposition (SVD) necessary for SBT can be omitted by utilizing the Smith method output in each Newton iteration, thereby significantly speeding up the model reduction process.
Thu, 01 Jan 2004 00:00:00 GMThttp://hdl.handle.net/10722/458552004-01-01T00:00:00Z
- New simulation methodology of 3D surface roughness loss for interconnects modelinghttp://hdl.handle.net/10722/61993Title: New simulation methodology of 3D surface roughness loss for interconnects modeling
Authors: Chen, Q; Wong, N
Abstract: As clock frequencies exceed giga-Hertz, the extra power loss due to conductor surface roughness in interconnects and packagings is more evident and thus demands a proper accounting for accurate prediction of signal integrity and energy consumption. Existing techniques based on analytical approximation often suffer from a narrow valid range, i.e., small or large limit of roughness. In this paper, we propose a new simulation methodology for surface roughness loss that is applicable to general surface roughness and a wide frequency range. The method is based on 3D statistical modeling of surface roughness and the numerical solution of scalar wave modeling (SWM) with the method of moments (MOM). The spectral stochastic collocation method (SSCM) is applied in association of random surface modeling to avoid the time-consuming Monte-Carlo (MC) simulation. Comparisons with existing methods in their respective valid region then verify the effectiveness of our approach. © 2009 EDAA.
Thu, 01 Jan 2009 00:00:00 GMThttp://hdl.handle.net/10722/619932009-01-01T00:00:00Z
- An efficient Homotopy-based Poincare-Lindstedt method for the periodic steady-state analysis of nonlinear autonomous oscillatorshttp://hdl.handle.net/10722/232362Title: An efficient Homotopy-based Poincare-Lindstedt method for the periodic steady-state analysis of nonlinear autonomous oscillators
Authors: Chen, Z; Batselier, K; Liu, H; Wong, N
Abstract: The periodic steady-state analysis of nonlinear systems has always been an important topic in electronic design automation (EDA). For autonomous systems, the mainstream approaches, like shooting Newton and harmonic balance, are difficult to employ since the period itself becomes an unknown. This paper presents an innovative state-space homotopy-based Poincar'e-Lindstedt method, with a novel Pad'e approximation of the stretched time axis, that effectively overcomes this hurdle. Examples demonstrate the excellent efficiency and scalability of the proposed approach.
Description: Session 3C - Pursuing System to Circuit Level Optimality in Timing and Power Integrity: no. 3C-4
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10722/2323622017-01-01T00:00:00Z
- STORM: a nonlinear model order reduction method via symmetric tensor decompositionhttp://hdl.handle.net/10722/216394Title: STORM: a nonlinear model order reduction method via symmetric tensor decomposition
Authors: Deng, J; Liu, H; Batselier, K; Kwok, YK; Wong, N
Abstract: Nonlinear model order reduction has always been a challenging but important task in various science and engineering fields. In this paper, a novel symmetric tensor-based orderreduction method (STORM) is presented for simulating largescale nonlinear systems. The multidimensional data structure of symmetric tensors, as the higher order generalization of symmetric matrices, is utilized for the effective capture of highorder nonlinearities and efficient generation of compact models. Compared to the recent tensor-based nonlinear model order reduction (TNMOR) algorithm [1], STORM shows advantages in two aspects. First, STORM avoids the assumption of the existence of a low-rank tensor approximation. Second, with the use of the symmetric tensor decomposition, STORM allows significantly faster computation and less storage complexity than TNMOR. Numerical experiments demonstrate the superior computational efficiency and accuracy of STORM against existing nonlinear model order reduction methods.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10722/2163942015-01-01T00:00:00Z
- Improved roundoff noise performance in a direct-form IIR filter using a modified delta operatorhttp://hdl.handle.net/10722/46232Title: Improved roundoff noise performance in a direct-form IIR filter using a modified delta operator
Authors: Wong, N; Ng, TS
Abstract: Among various direct-form delta operator filters, the delta direct-form II transposed (δDFIIt) has been shown to produce the lowest roundoff noise in finite-word-length implementations. Recent analyses focus on the optimization of the free parameter Δ of the delta operator, with scaling of the structure to prevent arithmetic overflow. This paper proposes a modified δDFIIt second-order section in which the Δs at different branches are separately optimized to further suppress roundoff noise gain. Noise variance plots against pole locations are presented. Closed-form expressions for the optimal filter coefficients are derived and reduction of noise gain is confirmed by numerical examples.
Mon, 01 Jan 2001 00:00:00 GMThttp://hdl.handle.net/10722/462322001-01-01T00:00:00Z
- Robust simulation methodology for surface-roughness loss in interconnect and package modelingshttp://hdl.handle.net/10722/129192Title: Robust simulation methodology for surface-roughness loss in interconnect and package modelings
Authors: Chen, Q; Choi, HW; Wong, N
Abstract: In multigigahertz integrated-circuit design, the extra energy loss caused by conductor surface roughness in metallic interconnects and packagings is more evident than ever before and demands explicit consideration for accurate prediction of signal integrity and energy consumption. Existing techniques based on analytical approximation, despite simple formulations, suffer from restrictive valid ranges, namely, either small or large roughness/frequencies. In this paper, we propose a robust and efficient numerical-simulation methodology applicable to evaluating general surface roughness, described by parameterized stochastic processes, across a wide frequency band. Traditional computation-intensive electromagnetic simulation is avoided via a tailored scalar-wave modeling to capture the power loss due to surface roughness. The spectral stochastic collocation method is applied to construct the complete statistical model. Comparisons with full wave simulation as well as existing methods in their respective valid ranges then verify the effectiveness of the proposed approach. © 2009 IEEE.
Thu, 01 Jan 2009 00:00:00 GMThttp://hdl.handle.net/10722/1291922009-01-01T00:00:00Z
- A generalized direct-form delta operator-based IIR filter with minimum noise gain and sensitivityhttp://hdl.handle.net/10722/42898Title: A generalized direct-form delta operator-based IIR filter with minimum noise gain and sensitivity
Authors: Wong, N; Ng, TS
Abstract: This brief presents the derivation of an arbitrary order delta operator-based direct-form IIR filter with minimum roundoff noise gain and sensitivity. It utilizes the concept of different coupling coefficients at different branch nodes for better noise gain suppression. Two possible structures for realizing the inverse delta operator are considered and procedures for calculating the optimal filter coefficients are given. By means of state-space representation and matrix manipulation, it is also shown that expressions for sensitivity measures of different filter coefficients and their corresponding roundoff noise gain expressions are the same. This enables the simultaneous minimization of sensitivity and noise power for the proposed generalized filter structure.
Mon, 01 Jan 2001 00:00:00 GMThttp://hdl.handle.net/10722/428982001-01-01T00:00:00Z
- Discussion of "a half-size singularity test matrix for fast and reliable passivity assessment of rational models"http://hdl.handle.net/10722/129196Title: Discussion of "a half-size singularity test matrix for fast and reliable passivity assessment of rational models"
Authors: Wong, N; Zhang, Z
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10722/1291962010-01-01T00:00:00Z
- Two algorithms for fast and accurate passivity-preserving model order reductionhttp://hdl.handle.net/10722/44741Title: Two algorithms for fast and accurate passivity-preserving model order reduction
Authors: Wong, N; Balakrishnan, V; Koh, CK; Ng, TS
Abstract: This paper presents two recently developed algorithms for efficient model order reduction. Both algorithms enable the fast solution of continuous-time algebraic Riccati equations (CAREs) that constitute the bottleneck in the passivity-preserving balanced stochastic truncation (BST). The first algorithm is a Smith-method-based Newton algorithm, called Newton/Smith CARE, that exploits low-rank matrices commonly found in physical system modeling. The second algorithm is a project-and-balance scheme that utilizes dominant eigenspace projection, followed by a simultaneous solution of a pair of dual CAREs through completely separating the stable and unstable invariant subspaces of a Hamiltonian matrix. The algorithms can be applied individually or together. Numerical examples show the proposed algorithms offer significant computational savings and better accuracy in reduced-order models over those from conventional schemes. © 2006 IEEE.
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/10722/447412006-01-01T00:00:00Z
- A signomial programming approach for binary image restoration by penalized least squareshttp://hdl.handle.net/10722/57451Title: A signomial programming approach for binary image restoration by penalized least squares
Authors: Shen, Y; Lam, EY; Wong, N
Abstract: The authors present a novel optimization approach, using signomial programming (SP), to restore noise-corrupted binary and grayscale images. The approach requires the minimization of a penalized least squares functional over binary variables, which has led to the design of various approximation methods in the past. In this brief, we minimize the functional as a SP problem which is then converted into a reversed geometric programming (GP) problem and solved using standard GP solvers. Numerical experiments show that the proposed approach restores both degraded binary and grayscale images with good accuracy, and is over 20 times faster than the positive semidefinite programming approach. © 2007 IEEE.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/10722/574512008-01-01T00:00:00Z
- An adaptive dynamical low-rank tensor approximation scheme for fast circuit simulationhttp://hdl.handle.net/10722/216392Title: An adaptive dynamical low-rank tensor approximation scheme for fast circuit simulation
Authors: Batselier, K; Chen, Q; Wong, N
Abstract: Tensors, as higher order generalization of matrices, have received growing attention due to their readiness in representing multidimensional data intrinsic to numerous engineering problems. This paper develops an efficient and accurate dynamical update algorithm for the low-rank mode factors. By means of tangent space projection onto the low-rank tensor manifold, the repeated computation of a full tensor Tucker decomposition is replaced with a much simpler solution of nonlinear differential equations governing the tensor mode factors. A worked-out numerical example demonstrates the excellent efficiency and scalability of the proposed dynamical approximation scheme.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10722/2163922015-01-01T00:00:00Z
- STAVES: speedy tensor-aided Volterra-based electronic simulatorhttp://hdl.handle.net/10722/216393Title: STAVES: speedy tensor-aided Volterra-based electronic simulator
Authors: Liu, H; Xiong, X; Batselier, K; Jiang, L; Daniel, L; Wong, N
Abstract: Volterra series is a powerful tool for blackbox macromodeling of nonlinear devices. However, the exponential complexity growth in storing and evaluating higher order Volterra kernels has limited so far its employment on complex practical applications. On the other hand, tensors are a higher order generalization of matrices that can naturally and efficiently capture multidimensional data. Significant computational savings can often be achieved when the appropriate low-rank tensor decomposition is available. In this paper we exploit a strong link between tensors and frequency-domain Volterra kernels in modeling nonlinear systems. Based on such link we have developed a technique called speedy tensor-aided Volterra-based electronic simulator (STAVES) utilizing high-order Volterra transfer functions for highly accurate time-domain simulation of nonlinear systems. The main computational tools in our approach are the canonical tensor decomposition and the inverse discrete Fourier transform. Examples demonstrate the efficiency of the proposed method in simulating some practical nonlinear circuit structures.
Description: Accepted Paper no. 228
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10722/2163932015-01-01T00:00:00Z
- Multiplierless synthesis of multiple constant multiplications using common subexpression sharing with genetic algorithmhttp://hdl.handle.net/10722/118351Title: Multiplierless synthesis of multiple constant multiplications using common subexpression sharing with genetic algorithm
Authors: Ho, AYH; Lei, CU; Wong, N
Abstract: In the context of multiple constant multiplications (MCM) design, we propose a novel common subexpression elimination (CSE) algorithm that models synthesis of coefficients into an estimated cost function. Although the proposed algorithm generally does not guarantee an optimum solution, it is capable of finding the minimum/ minima of the function in practically sized problems. In our design examples that have known optimal solutions, syntheses of coefficients using the proposed method match the optimal results in a defined search space. We also discover the relationship and propose an improvement search space for optimization that combines all minimal signed digit (MSD) representations, as well as the shifted sum (difference) of coefficients to explore the hidden relationship. In some cases, the proposed feasible solution space further reduces the number of adders/subtractors in the synthesis of MCM from all MSD representations.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/10722/1183512008-01-01T00:00:00Z
- Efficient numerical modeling of random rough surface effects for interconnect internal impedance extractionhttp://hdl.handle.net/10722/98855Title: Efficient numerical modeling of random rough surface effects for interconnect internal impedance extraction
Authors: Chen, Q; Wong, N
Abstract: This paper proposes an efficient model for numerically evaluating the impact of random surface roughness on the internal impedance for large-scale interconnect structures. The effective resistivity (ER) and effective permeability (EP) are numerically formulated to avoid the computationally prohibitive global discretization, while maintaining the model accuracy and flexibility. A modified stochastic integral equation (SIE) method is proposed to significantly speed up the computation for the mean values of ER and EP under the assumption of random surface roughness. Numerical experiments then verify the efficacy of our approach. ©2008 IEEE.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/10722/988552008-01-01T00:00:00Z