Available energy of improper lossless LLTIP one‐ports

A method for evaluating the available energy of a class of black‐box circuit components is proposed. The class consists of those linear lumped time‐invariant passive one‐ports of any order that are improper and lossless. The approach requires the utilization of tools and techniques from the calculus of variations (Euler–Lagrange equations and natural transversality conditions) and involves rather demanding algebraic and integro‐differential manipulations. However, the final formula for the available energy has the simple structure of a quadratic form in the one‐port external state vector, relatively easy to use or to implement. The various steps of the approach developed are illustrated through examples. Furthermore, to evidence the difference between available energy and stored energy, two degenerate and one non‐degenerate open‐box one‐ports are discussed in some detail. Copyright © 2015 John Wiley & Sons, Ltd.     

A study on the tie‐set graph theory and network flow optimization problems

Aiming at establishing a firm basic theory to ring‐based information network management systems, our paper proposes a tie‐set graph theory. We define a binary vector representing a tie‐set in a biconnected undirected graph G=(V,E) as a tie‐set vector. The set of tie‐set vectors forms a vector space over the proposed law of composition, then a basis of the vector space, μ linear independent tie‐set vectors, is defined as a tie‐set basis. The essential key concept in our theory is a tie‐set graph, which has a one‐to‐one correspondence to a tie‐set basis and represents a relation between two tie‐set vectors of the basis. Some important properties of tie‐set graphs and their application to survivable mesh networks in modern high‐speed backbone networks are also presented. Furthermore, as a general approach to network flow optimization problems, tie‐set flow vector space is proposed based on the tie‐set graph theory. A distributed algorithm for the network flow optimization problems and its application are also presented in this paper. Copyright © 2004 John Wiley & Sons, Ltd.     

Time‐domain properties of reactive dual circuits

The present work explores some effects of the replacement of capacitors by inductors and vice versa in state and semistate models of lumped circuits. Such a replacement, when performed together with an inversion of the capacitance and inductance matrices, yields a transformation of the form λ→λ^?1 in the system spectra. In the semistate context, this covers in particular extremal cases in which null eigenvalues or infinite ones with higher index appear in the matrix pencil associated with the model; these cases describe certain pathological circuit configurations. This approach leads to a discussion of new properties of strictly passive circuits; specifically, from the known fact that the index of strictly passive circuits does not exceed two, we derive that the index of null eigenvalues in this setting cannot exceed one. This precludes in particular Takens‐Bogdanov degeneracies, defined by an index‐two double‐zero eigenvalue, in strictly passive circuits. Although the results are addressed in a linear context, they can be extended via linearization to non‐linear problems, as it is the case in the transformation of singularity‐induced bifurcation phenomena into steady bifurcations discussed at the end of the paper. Copyright © 2006 John Wiley & Sons, Ltd.     

M‐matrices and global convergence of discontinuous neural networks

The paper considers a general class of neural networks possessing discontinuous neuron activations and neuron interconnection matrices belonging to the class of M‐matrices or H‐matrices. A number of results are established on global exponential convergence of the state and output solutions towards a unique equilibrium point. Moreover, by exploiting the presence of sliding modes, conditions are given under which convergence in finite time is guaranteed. In all cases, the exponential convergence rate, or the finite convergence time, can be quantitatively estimated on the basis of the parameters defining the neural network. As a by‐product, it is proved that the considered neural networks, although they are described by a system of differential equations with discontinuous right‐hand side, enjoy the property of uniqueness of the solution starting at a given initial condition. The results are proved by a generalized Lyapunov‐like approach and by using tools from the theory of differential equations with discontinuous right‐hand side. At the core of the approach is a basic lemma, which holds under the assumption of M‐matrices or H‐matrices, and enables to study the limiting behaviour of a suitably defined distance between any pair of solutions to the neural network. Copyright © 2006 John Wiley & Sons, Ltd.     

A high‐order discontinuous Galerkin method with time‐accurate local time stepping for the Maxwell equations

We present an explicit numerical method to solve the time‐dependent Maxwell equations with arbitrary high order of accuracy in space and time on three‐dimensional unstructured tetrahedral meshes. The method is based on the discontinuous Galerkin finite element approach, which allows for discontinuities at grid cell interfaces. The computation of the flux between the grid cells is based on the solution of generalized Riemann problems, which provides simultaneously a high‐order accurate approximation in space and time. Within our approach, we expand the solution in a Taylor series in time, where subsequently the Cauchy–Kovalevskaya procedure is used to replace the time derivatives in this series by space derivatives. The numerical solution can thus be advanced in time in one single step with high order and does not need any intermediate stages, as needed, e.g. in classical Runge–Kutta‐type schemes. This locality in space and time allows the introduction of time‐accurate local time stepping (LTS) for unsteady wave propagation. Each grid cell is updated with its individual and optimal time step, as given by the local Courant stability criterion. On the basis of a numerical convergence study we show that the proposed LTS scheme provides high order of accuracy in space and time on unstructured tetrahedral meshes. The application to a well‐acknowledged test case and comparisons with analytical reference solutions confirm the performance of the proposed method. Copyright © 2008 John Wiley & Sons, Ltd.     

Stackable ROADM with optical amplifier for use in IP‐Over‐CWDM ring networks

A stackable module with a bidirectional coarse wavelength division multiplexing (CWDM) amplifier is proposed to introduce the optical amplifier into an stackable‐reconfigurable optical add/drop multiplexers (S‐ROADM) for use in an IP‐over‐CWDM ring network, and the performance is evaluated experimentally. Packet transfer changes are monitored during the lightpath reconfiguration, which needs optical amplification. The result clarify that the lightpaths are reconfigured successfully, including the remote activation of the amplifiers. As a result, the stackable feature of the amplifier module enables us to provide a cost‐effective introduction into the network on an implement‐it‐when‐necessary base in a fully compatible way with the existing S‐ROADM modules when constructing the S‐ROADM with an amplifier. Therefore, the amplifier module can be used in the same way as the ROADM modules to construct the S‐ROADM, providing manually adding capability of the amplifier to in‐service networks. Thus, the amplifier module has a big advantage to use it flexibly and economically in the IP‐over‐CWDM ring networks. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Design and analysis of power‐CMOS‐gate‐based switched‐capacitor DC–DC converter with step‐down and step‐up modes

A unified multi‐stage power‐CMOS‐transmission‐gate‐based quasi‐switched‐capacitor (QSC) DC–DC converter is proposed to integrate both step‐down and step‐up modes all in one circuit configuration for low‐power applications. In this paper, by using power‐CMOS‐transmission‐gate as a bi‐directional switch, the various topologies for step‐down and step‐up modes can be integrated in the same circuit configuration, and the configuration does not require any inductive elements, so the IC fabrication is promising for realization. In addition, both large‐signal state‐space equation and small‐signal transfer function are derived by state‐space averaging technique, and expressed all in one unified formulation for both modes. Based on the unified model, it is all presented for control design and theoretical analysis, including steady‐state output and power, power efficiency, maximum voltage conversion ratio, maximum power efficiency, maximum output power, output voltage ripple percentage, capacitance selection, closed‐loop control and stability, etc. Finally, a multi‐stage QSC DC–DC converter with step‐down and step‐up modes is made in circuit layout by PSPICE tool, and some topics are discussed, including (1) voltage conversion, output ripple percentage, and power efficiency, (2) output robustness against source noises and (3) regulation capability of converter with loading variation. The simulated results are illustrated to show the efficacy of the unified configuration proposed. Copyright © 2003 John Wiley & Sons, Ltd.     

Figures‐of‐merit genetic extraction for InGaAs lasers,SiGe low‐noise amplifiers,and ZnSe/Ge/GaAs HBTs

In this paper, we have successfully developed an intellectual parameter‐extraction methodology on the basis of a genetic algorithm (GA), involving the efficient search‐space separation and local‐minima‐convergence prevention schemes. Via an evolutionary simulation tool complemented with appropriate analytic equations, the enhanced approach has been applied to determine the significant figures‐of‐merit (FoMs), including internal quantum efficiency (η_i) as well as transparency current density (J_tr) of semiconductor lasers, minimum noise figure (NF_min) as well as associated available gain (G_A,assoc) of low‐noise amplifiers (LNAs), and DC as well as AC characteristics of heterojunction bipolar transistors (HBTs). For the first time, demonstrated FoM‐extraction results, which coincide well with the actually measured data, for state‐of‐the‐art InGaAs quantum‐well lasers, advanced SiGe LNAs, and abrupt ZnSe/Ge/GaAs HBTs are simultaneously presented to validate this multi‐parameter analysis and robust optimization. Copyright © 2011 John Wiley & Sons, Ltd.     

Frequency domain subspace identification with the aid of the w‐operator

Frequency domain subspace identification algorithms have been studied recently by several researchers in the literature, motivated by the significant development of the more popular time domain counterparts. Usually, this class of methods are focused on discrete‐time models, since in the case of continuous‐time models, the data matrices often become ill‐conditioned if we simply rewrite the Laplace operator s as s = jω, where ω denotes the frequency. This paper proposes an efficient and convenient approach to frequency domain subspace identification for continuous‐time systems. The operator w = (s−α)/(s+α) is introduced to avoid the ill‐conditioned problem. Hence, the system can be identified based on a state‐space model in the w‐operator. Then the estimated w‐operator state‐space model can be transformed back to the common continuous‐time state‐space model. An instrumental variable matrix in the frequency domain is also proposed to obtain consistent estimates of the equivalent system matrices in the presence of measurement noise. Simulation results are included to verify the efficiency of the proposed algorithms. © 2000 Scripta Technica, Electr Eng Jpn, 132(1): 46–56, 2000     

Implementation of the stretched co‐ordinate‐based PML for waveguide structures in TLM

A novel implementation of the stretched co‐ordinate‐based perfectly matched layer (SCB PML) is presented to terminate waveguide structures in transmission‐line modelling (TLM). A generalized SCB PML, the complex frequency shifted PML (CFS PML) is also implemented to investigate its performance for evanescent waves. State variables in the Z‐domain are employed to obtain update equations for incident voltage pulses. Numerical results for a rectangular waveguide filled with a lossy medium as well as free space, and for a parallel plate waveguide are presented. Copyright © 2004 John Wiley & Sons, Ltd.     

Frequency‐weighted model reduction via interpolation

We propose a numerical method of frequency‐weighted model reduction. The model to be reduced (an original model) is a stable SISO discrete‐time model described by high‐order state‐space equations. We design the reduced‐order model so that it can interpolate 1st‐ and 2nd‐order information of the original model at complex frequency points (interpolation points) in the unit circle. The characteristics of the reduced‐order model greatly depend on the choice of the interpolation points. The proposed model reduction method is a numerical one that chooses the interpolation points by searching in the unit circle to find the reduced‐order model such that L_∞‐norm of the reduction error is less than a prescribed value. This method has the following features that show that it is an effective numerical method of the frequency‐weighted model reduction. i) The reduced‐order model is guaranteed to be stable. ii) The procedure for finding the reduced‐order model is simple and requires a relatively small amount of computation. iii) The order of the reduced‐order model can be controlled by choosing the number of interpolation points. © 1998 Scripta Technica, Electr Eng Jpn, 126(2): 31–39, 1999     

Constructing numerically stable Kalman filter‐based algorithms for gradient‐based adaptive filtering

This paper addresses the numerical aspects of adaptive filtering (AF) techniques for simultaneous state and parameters estimation arising in the design of dynamic positioning systems in many areas of research. The AF schemes consist of a recursive optimization procedure to identify the uncertain system parameters by minimizing an appropriate defined performance index and the application of the Kalman filter (KF) for dynamic positioning purpose. The use of gradient‐based optimization methods in the AF computational schemes yields to a set of the filter sensitivity equations and a set of matrix Riccati‐type sensitivity equations. The filter sensitivities evaluation is usually carried out by the conventional KF, which is known to be numerically unstable, and its derivatives with respect to unknown system parameters. Recently, a novel square‐root approach for the gradient‐based AF by the method of the maximum likelihood has been proposed. In this paper, we show that various square‐root AF schemes can be derived from only two main theoretical results. This elegant and simple computational technique replaces the standard methodology based on direct differentiation of the conventional KF equations (with their inherent numerical instability) by advanced square‐root filters (and its derivatives as well). As a result, it improves the robustness of the computations against round off errors and leads to accurate variants of the gradient‐based AFs. Additionally, such methods are ideal for simultaneous state estimation and parameter identification because all values are computed in parallel. The numerical experiments are given. Copyright © 2015 John Wiley & Sons, Ltd.     

Design equations for fractional‐order sinusoidal oscillators: Four practical circuit examples

Four practical sinusoidal oscillators are studied in the general form where fractional‐order energy storage elements are considered. A fractional‐order element is one whose complex impedance is given by Z = a(jω)^±α, where a is a constant and α is not necessarily an integer. As a result, these oscillators are described by sets of fractional‐order differential equations. The integer‐order oscillation condition and oscillation frequency formulae are verified as special cases. Numerical and PSpice simulation results are given. Experimental results are also reported for a selected Wien‐bridge oscillator. Copyright © 2007 John Wiley & Sons, Ltd.     

A matrix pencil approach to the local stability analysis of non‐linear circuits

This paper addresses local stability issues in non‐linear circuits via matrix pencil theory. The limitations of the state–space approach in circuit modelling have led to semistate formulations, currently framed within the context of differential‐algebraic equations (DAEs). Stability results for these DAE models can be stated in terms of matrix pencils, avoiding the need for state–space reductions which are not advisable in actual circuit simulation problems. The stability results here presented are applied to electrical circuits containing non‐linear devices such as Josephson junctions or MOS transistors. Copyright © 2004 John Wiley & Sons, Ltd.     

Steady‐state solutions of a voltage source converter with dq‐frame controllers by means of the time‐domain method

A voltage source converter (VSC) is one of the most widely used power converters in a power system. In this paper, a time‐domain‐based accelerated steady‐state method is proposed to solve for a closed‐loop pulse‐width modulated (PWM) VSC with dq‐frame controllers, which is able to account for the harmonic interactions between the converter and the rest of the power network, between the AC and DC sides of a VSC, and between the converter and its controllers. The proposed time‐domain method is based on the modified time‐domain shooting method, where the Jacobian matrix is updated by the quasi‐Newtons method. This will drastically increase the computation efficiency as it avoids re‐evaluating and inverting the Jacobian matrix, whose size is usually very large for a PWM‐VSC due to high number of times of switching. All the results are shown to be consistent with those obtained by a PSCAD/EMTDC model, which has been validated with the experiment in a previous publication. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Digital filter design with state space method for 1‐bit signal processing based on delta‐sigma modulation

One‐bit signal processing based on delta‐sigma modulation has been studied for hardware implementation of signal processing systems. In the 1‐bit signal processing, finite word‐length problems such as overflow and coefficient quantization error occur. To solve the problems, a new design method with state space is proposed in this paper. Digital filters are designed to show the feasibility of the method. First, the L₁/L₂‐sensitivity is shown to evaluate coefficient quantization error and L₂ scaling constraints to prevent overflow. Second, a state space equation is presented and the L₁/L₂‐sensitivity and L₂‐scaling constraints are extended to take the filter structure and oversampling effects into account. Finally, the proposed method is shown to attain a higher SNR than conventional ones. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(4): 48–56, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21075     

Optimal filtering,fault detection and isolation for linear discrete‐time systems in a noisy environment

In this paper the state observer design and the fault detection and isolation problems are investigated in the context of linear discrete‐time state‐space models whose state equations are affected by (actuator) faults and disturbances. Model as well as measurement errors, described as zero‐mean white Gaussian noise, are also assumed to act additively on the state and on the output equations, respectively. Upon introducing several deterministic and stochastic goals, that constitute the mathematical formalization of very natural and practical requirements, necessary and sufficient conditions for the existence of an asymptotic state observer and an observer‐based fault detector and isolator, that achieve the above goals, are finally derived and a constructive procedure is described. Copyright © 2003 John Wiley & Sons, Ltd.     

Mode dynamics in fourth‐order LC oscillators

We present a complete analysis of single and concurrent modes in fourth‐order LC‐voltage‐controlled oscillators ( VCOs), which are increasingly applied in dual‐band communication systems. We give a procedure based on the averaging method that simplifies the derivation of the abridged equations, which are derived without resorting to a change of co‐ordinates. The amplitudes of the oscillatory modes in steady state and in transient are found in explicit form. Conditions for the stability of the single and concurrent modes are derived, which apply to any active one‐port dual‐band LC‐VCO and allow one to predict the nonlinearities ensuring the occurrence of a stable concurrent mode. Numerical and experimental results show a good accuracy of the presented formulas. Copyright © 2016 John Wiley & Sons, Ltd.