Gabriela Ciuprina

Use of intelligent-particle swarm optimization in electromagnetics

The paper describes a new stochastic heuristic algorithm for global optimization. The new optimization algorithm, called intelligent-particle swarm optimization (IPSO), offers more intelligence to particles by using concepts such as: group experiences, unpleasant memories (tabu to be avoided), local landscape models based on virtual neighbors, and memetic replication of successful behavior parameters. The new individual complexity is amplified at the group level and consequently generates a more efficient optimization procedure. A simplified version of the IPSO algorithm was implemented and compared with the classical PSO algorithm for a simple test function and for the Loneys solenoid.

Compact modeling and fast simulation of on-chip interconnect lines

An efficient methodology to extract compact models for microstrip lines on lossy silicon substrate is presented. The transversal magnetic field equations are solved by dual finite integration technique (dFIT), a numerical method which allows the accuracy control of the computed frequency dependent line parameters. Several techniques are used to accelerate the process of p.u.l. parameters extraction, such as minimal virtual boundary, minimal mesh and minimal frequency samples set. The solution of the transmission line equations with frequency dependent parameters is then approximated by a rational function of appropriate degree in order to extract the compact model and its SPICE equivalent circuit. The behavior of the obtained compact model of order 10 shows good agreement with respect to the measured data

Reduced Order Models of On-Chip Passive Components and Interconnects, Workbench and Test Structures

The models of passive components have to describe all relevant electromagnetic field effects at high frequency encountered inside these devices. These effects are quantified by the Maxwell equations of the electromagnetic field in full wave (FW) regime. Therefore, at the first level of approximation, the model of a passive device is defined by an electromagnetic (EM) field problem, formulated by Maxwell partial differential equations with appropriate boundary and initial conditions. This problem defines a consistent I/O system which has a unique response, described by the output signals, for any input signal applied as terminal excitations. This system with distributed parameters has an infinite dimension state space, but a finite number of inputs and outputs related to the device terminals. The next level of approximation in the modeling process (Fig. 1) results by applying a numerical method to discretize the continuous model defined above. This step associates a simpler ODE to the original PDE model, actually a system of DAE. It is an important step ahead, reducing the infinite dimensional state-space which is specific to distributed systems to a finite one. However, the size of the state-space is still too large for the designers needs. It has an order similar to the number of DOFs associated to the cells, finite elements used to discretize the computational domain.

Models for integrated components coupled with their EM environment

Purpose – The main aim of this study is the modelling of the interaction of on‐chip components with their electromagnetic environment.Design/methodology/approach – The integrated circuit is decomposed in passive and active components interconnected by means of terminals and connectors which represent intentional and parasitic couplings of a capacitive and inductive nature. Reduced order models are extracted independently for each component.Findings – The paper shows that one of the main theoretical problems encountered in the modelling of RF components is the difficulty to define a unique terminal voltage, independent of the integration path (this independence being a condition to allow the connection of the component in an electric circuit, where the voltage does not depend of the path shape). The concept of an electromagnetic circuit element that allows the interconnection between IC models is proposed as a solution for this drawback. The system is described either with EM field models, or by electric/m...

Absorbing boundary conditions for compact modeling of on‐chip passive structures

Purpose – The paper has the purpose of proposing a new open boundary condition to be used in conjunction with the finite integration technique (FIT) for the modelling of passive on‐chip components.Design/methodology/approach – This boundary condition is ensured by using a virtual layer that surrounds the computational domain.Findings – The paper proves which are the optimal material properties of the equivalent layer of open boundary.Practical implications – When modelling passive on‐chip components with FIT, the method proposed is more efficient than the strategic dual image technique.Originality/value – The paper shows the advantage of this approach – that the analysis algorithm remains unchanged, while saving the field‐circuit compatibility properties, such as current conservation.

Parametric Models Based on Sensitivity Analysis for Passive Components

Passive components with significant high frequency field effects have to be modeled taking into consideration full wave electromagnetic field equations. Such a field formulation with appropriate electromagnetic circuit element boundary conditions is numerically analyzed in the time domain with the finite integral technique, a sparse state-space representation of the component being obtained. The novelty of the presented approach is the use of model parameterization and the extraction of the model sensitivities needed by parametric model order reduction procedures. The paper investigates the validity of first order Taylor Series expansion with respect to the parameters as approximation for the extracted semi-state space models.

Parametric Models Based on the Adjoint Field Technique for RF Passive Integrated Components

Taking into consideration the variability specific to the nowadays nanotechnologies, the fast extraction of parametric models is a must for the present VLSI and radio-frequency (RF)-integrated-circuit (IC) design environments. The major contribution of the paper is a new, effective methodology for the extraction of parametric compact models for passive RF integrated components with field effects, valid for high-frequency broad range. The proposed numeric method is systematically based on a dual approach, which provides two complementary approximations of the exact solution. Duality is applied both to the spaces where the discrete solution is found as well as to the open boundary conditions. The adjoint field technique is applied in an original manner to the finite-integral techniques to handle the parameter variability of the extracted model. The new method needs much less computing resources for modeling than other numerical methods.

Fast Extraction of Static Electric Parameters with Accuracy Control

The paper presents an efficient numerical method to extract accurate R, L, C parameters of passive on-chip structures. This method is based on two main original ideas. First, the accuracy is controlled by using two complementary approaches based on scalar and vector potential, which provide lower and upper bounds for the extracted parameter. The convergence is accelerated by using the Richardson extrapolation of the average value of the two complementary bounds. Second, the field equations are solved by multigrid finite element method with local adaptive mesh subgriding. The refining process is stopped as soon as the desired accuracy is reached.

Domain Partitioning Based Parametric Models for Passive On-Chip Components

This paper shows how to obtain models for passive integrated components that take into consideration the variability inherent to their design. To achieve this, the computational domain is split into sub-domains in which the electromagnetic circuit element (EMCE) formulation is used. The variability is described by using first order Taylor Series representation for the semi-state space matrices. The novelty of the paper is that it describes how the EMCE based parametric models can be obtained. The parametric sub-models can be interconnected afterwards to obtain a global parametric model that can be simulated or reduced. The advantage of this approach is that it bears an inherent parallelism. The sub-models can be treated independently both from the point of view of the variability, and from the point of view of electromagnetic field formulation. Both aspects are illustrated with a simple test case as well as a real benchmark designed and characterized at austriamicrosystems.

Effective Domain Partitioning With Electric and Magnetic Hooks

This paper discusses interface conditions used in a domain partitioning method and their approximation with a reduced number of degrees of freedom called hooks. In the electrostatic and magnetostatic cases, electric or magnetic hook-connectors are, respectively, used to describe interactions. Better numerical results are obtained in the full wave regime by using both electric and magnetic hooks. This paper proposes an efficient approximation of the interface conditions by using a coarser grid on this surface. We have shown that the interface tends to become transparent for the electromagnetic (EM) field, when the number of hooks is increased and consider this convergence property as the main result of the paper. The proposed domain partitioning (DP) method was successfully applied as a particular domain decomposition (DD) technique for the EM modeling with parallel algorithms of RF-IC components. Unlike DD which is an iterative approach, the new DP approach is a direct one. The sub-domain models being independently extracted, DP is more effective and suitable for parallelization. The open problem of hooks identification is reformulated as a discrete optimization problem.