State-of-the-art harmonic-balance simulation of forced nonlinearmicrowave circuits by the piecewise technique

The theoretical foundations and the numerical performance of an advanced nonlinear circuit simulator based on the piecewise harmonic-balance (HB) technique are discussed. The exact computation of the Jacobian matrix for Newton-iteration based HB simulation and the related conversion-matrix technique for fast mixer analysis are formulated in a general form. Convergence problems at high drive levels are solved by a parametric formulation of the device models coupled with an advanced norm-reducing iteration. A physics-based approximation is shown to allow the HB equations to be effectively decoupled in many practical cases, bringing large-sized jobs, such as pulsed-RF analysis, within the reach of ordinary workstations. The exact Jacobian is used in conjunction with an exact formula for the gradient of the objective function, to implement an efficient broadband nonlinear circuit optimization capability. Examples are presented     

Physics-based electron device modelling and computer-aided MMICdesign

On overview on the state of the art and future trends in physics-based electron device modelling for the computer-aided design of monolithic microwave ICs is provided. After a review of the main physics-based approaches to microwave modeling, special emphasis is placed on innovative developments relevant to circuit-oriented device performance assessment, such as efficient physics-based noise and parametric sensitivity analysis. The use of state-of-the-art physics-based analytical or numerical models for circuit analysis is discussed, with particular attention to the role of intermediate behavioral models in linking multidimensional device simulators with circuit analysis tools. Finally, the model requirements for yield-driven MMIC design are discussed, with the aim of pointing out the advantages of physics-based statistical device modeling; the possible use of computationally efficient approaches based on device sensitivity analysis for yield optimization is also considered     

Physics-based MCT circuit model using the lumped-charge modelingapproach

This paper presents a physics-based model of metal-oxide-semiconductor (MOS) controlled thyristor (MCT) using the lumped-charge modeling technique. As a relatively new power semiconductor device, little effort has been made thus far in creating an accurate model for simulation use. The only MCT model available to date is that using two bipolar transistors-a behavioral subcircuit model. This model works well for static operation, but has limitations in predicting the dynamic behavior of the device due to the omission of the internal device physics. The use of the lumped-charge modeling technique facilitates the inclusion of internal physical processes and the structural geometry of the device into the model. As a result, this technique provides a more realistic and accurate one-dimensional (1-D) model than any other presently available. This paper presents the successful implementation of the lumped-charge approach on hybrid bipolar-MOS power devices such as the MCT. Most importantly, this model is capable of predicting some dynamic soft-switching behavior of the device, which was never realizable by any SPICE-based simulators. The developed model is thoroughly verified through Saber simulation and experimentation     

Modeling of power diodes with the lumped-charge modeling technique

The lumped-charge modeling technique is used to build a simple, physics-based power diode model for circuit simulators. The model consists of simplified, but fundamental semiconductor device equations. The important characteristics of power diodes under static and dynamic conditions are obtained in this compact and efficient model     

Small-signal characterization of microwave and millimeter-waveHEMT's based on a physical model

A highly efficient generalized physics-based approach for small-signal characterization of FET devices is presented. A novel method is developed for extracting the frequency dependent two-port parameters from a single time-domain physical simulation based on a multi-signal excitation scheme. The technique is applied to simulating the frequency- and bias-dependent scattering parameters of HEMT's using a quasi-two-dimensional physical model that incorporates the main physical phenomena which govern the device behavior. A new carrier energy distribution model is presented which improves the accuracy of the physical model. An equivalent circuit is also generated from the physical dynamic simulation which can be used for predicting S-parameters and for indirect linking of the physical model to existing CAD tools. The unique formulation and efficiency of the present technique make it suitable for computer aided design of FET subsystems. The accuracy and flexibility of this approach is demonstrated by comparison of simulated results with measured data for a pulse doped pHEMT and uniformly doped GaAs channel HEMT     

A neural network modeling approach to circuit optimization andstatistical design

The trend of using accurate models such as physics-based FET models, coupled with the demand for yield optimization results in a computationally challenging task. This paper presents a new approach to microwave circuit optimization and statistical design featuring neural network models at either device or circuit levels. At the device level, the neural network represents a physics-oriented FET model yet without the need to solve device physics equations repeatedly during optimization. At the circuit level, the neural network speeds up optimization by replacing repeated circuit simulations. This method is faster than direct optimization of original device and circuit models. Compared to existing polynomial or table look-up models used in analysis and optimization, the proposed approach has the capability to handle high-dimensional and highly nonlinear problems     

A TCAD approach to the physics-based modeling of frequencyconversion and noise in semiconductor devices under large-signal forcedoperation

The paper presents a novel, unified technique to evaluate, through physics-based modeling, the frequency conversion and noise behavior of semiconductor devices operating in the large-signal periodic regime. Starting from the harmonic balance (HE) solution of the spatially discretized physics-based model under (quasi) periodic forced operation, frequency conversion at the device ports in the presence of additional input tones is simulated by application of the small-signal large-signal network approach to the model. Noise analysis under large-signal operation readily follows as a direct extension of classical approaches by application of the frequency conversion principle to the modulated microscopic noise sources and to the propagation of these to the external device terminals through a Green's function technique. An efficient numerical implementation is discussed within the framework of a drift-diffusion model and some examples are finally provided on the conversion and noise behavior of rf Si diodes     

DOE/Opt: a system for design of experiments, response surfacemodeling, and optimization using process and device simulation

Rapid modeling and optimization of manufacturing processes, devices, and circuits are required to support modern integrated circuit technology development and yield improvement. We have prototyped and applied an integrated system, called DOE/Opt, for performing Design of Experiments (DOE), Response Surface Modeling (RSM), and Optimization (Opt). The system to be modeled and optimized can be either physical or simulation based. Within the DOE/Opt system, coupling to external simulation or experimental tools is achieved via an embedded extension language based on Tcl. The external problem then appears to DOE/Opt as a model with user defined inputs and outputs. DOE/Opt is used to generate splits for experiments, to dynamically build and evaluate regression models from experimental runs, and to perform nonlinear constrained optimizations using either regression models or embedded executions. The intermediate regression modeling can appreciably accelerate the optimization task when simulation or physical experiments are expensive. The primary application of DOE/Opt has been to process optimization using coupled process and device simulation. DOE/Opt has also been applied to process and device simulator tuning, and to aid in device characterization. Such a DOE/Opt system is expected to augment the use of TCAD tools and to utilize data collected by CIM systems in support of process synthesis. We have demonstrated the application of the system to process parameter determination, simulator tuning, process control modeling, and statistical process optimization. We are extending the system to more fully support emerging device design and process synthesis methodologies     

Physics-based simulation techniques for small- and large-signal device noise analysis in RF applications

The paper presents a review on physics-based noise simulation techniques for RF semiconductor devices, starting with the small-signal case but with greater stress on noise in large-signal (quasi)-periodic operation. The nonautonomous (forced) operation case will be considered, which is relevant to all RF applications apart from oscillators. Besides their importance in device design, physics-based noise models can also suggest viable and correct strategies to implement circuit-oriented models, e.g., compact models. From this standpoint, the connection between physics-based and circuit-oriented modeling is discussed both in the small-signal and in the large-signal case, with particular stress on the treatment of colored noise in the large-signal periodic regime.     

The modeling, analysis, and design of filter-based parametricfrequency dividers

A technique for the design of filter-based parametric frequency dividers is discussed. The technique combines basic divider analysis with modern nonlinear simulation techniques. In essence, the procedure allows the completion of a successful design that is based on computer simulations, but requires little or no nonlinear optimization. Specifically, divider modeling, threshold, and efficiency are investigated, and a straightforward design strategy is given     

EMC and BEM engineering education: physics-based modeling, hands-on training, and challenges

Educational challenges in EMC-BEM engineering and related issues are discussed in this paper. The importance of physics-based modeling and hands-on training are emphasized. Characteristic cases in EMC tests, measurements, modeling, and simulation are presented. Finally, some suggestions and a short-course outline are given for modern EMC-BEM education.     

EMC and BEM engineering education: physics-based modeling, hands-on training, and challenges

Educational challenges in EMC-BEM engineering and related issues are discussed in this paper. The importance of physics-based modeling and hands-on training are emphasized. Characteristic cases in EMC tests, measurements, modeling, and simulation are presented. Finally, some suggestions and a short-course outline are given for modern EMC-BEM education.     

Modeling and Simulation of Electric and Hybrid Vehicles

This paper discusses the need for modeling and simulation of electric and hybrid vehicles. Different modeling methods such as physics-based Resistive Companion Form technique and Bond Graph method are presented with powertrain component and system modeling examples. The modeling and simulation capabilities of existing tools such as Powertrain System Analysis Toolkit (PSAT), ADvanced VehIcle SimulatOR (ADVISOR), PSIM, and Virtual Test Bed are demonstrated through application examples. Since power electronics is indispensable in hybrid vehicles, the issue of numerical oscillations in dynamic simulations involving power electronics is briefly addressed     

Efficient analytical formulation and sensitivity analysis of neuro-space mapping for nonlinear microwave device modeling

A new computer-aided design (CAD) method for automated enhancement of nonlinear device models is presented, advancing the concept of Neuro-space mapping (Neuro-SM). It is a systematic computational method to address the situation where an existing device model cannot fit new device data well. By modifying the current and voltage relationships in the model, Neuro-SM produces a new model exceeding the accuracy limit of the existing model. In this paper, a novel analytical formulation of Neuro-SM is proposed to achieve the same accuracy as the basic formulation of Neuro-SM (known as circuit-based Neuro-SM) with much higher computational efficiency. Through our derivations, the mapping between the existing (coarse) model and the overall Neuro-SM model is analytically achieved for dc, small-signal, and large-signal simulation and sensitivity analysis. The proposed analytical formulation is a significant advance over the circuit-based Neuro-SM, due to the elimination of extra circuit equations needed in the circuit-based formulation. A two-phase training algorithm utilizing gradient optimization is also developed for fast training of the analytical Neuro-SM models. Application examples on modeling heterojunction bipolar transistor (HBT), metal-semiconductor-field-effect transistor (MESFET), and high-electron mobility transmistor (HEMT) devices and the use of Neuro-SM models in harmonic balance simulations demonstrate that the analytical Neuro-SM is an efficient approach for modeling various types of microwave devices. It is useful for systematic and automated update of nonlinear device model library for existing circuit simulators.     

Full-wave electromagnetic simulation of millimeter-wave active devices and circuits

This paper discusses the most recent progress in developing effective physics-based models for devices operating at millimeter-wave frequencies. The model is based on coupling dynamic electromagnetic wave solutions with carrier transport models. The potentials of this modeling approach for both device simulation and the global simulation of millimeter-wave circuits are demonstrated. Results comparing the full-wave model developed with conventional electrostatic models are provided through the simulation of different microwave transistors. The ability of the model to detect traveling wave effects, such as phase mismatch between the input and output electrodes of a conventional transistor, and their effects on the device gain are also provided. Results from the simulation of an air-bridged gateMesfet, designed to reduce traveling wave effects in high frequency transistors and solve the problem associated with high gate resistance, are illustrated and discussed. Finally, results showing the ability of this technique to model the nonlinearity and the harmonic distortion are provided through the simulation of an amplifier circuit.     

A large-signal, analytic model for the GaAs MESFET

An analytic, large-signal model for the GaAs MESFET is presented. The device model is physics-based and describes the conduction and displacement currents of the FET as a function of instantaneous terminal voltages and their time derivatives. The model allows arbitrary doping profiles in the channel and is thus suitable for the optimization of ion-implanted and buried-channel FETs. It also accounts for charge accumulation in the conducting channel at high electric fields and the associated capacitance in a self-consistent manner. Theoretical predictions of the model are correlated with experimental data on X -band power FETs and excellent agreement is obtained     

A new analytical method of solving 2D Poisson''s equation in MOS devices applied to threshold voltage and subthreshold modeling

In this paper we present a new theoretical approach in MOS modeling to derive analytical, physics-based model equations for the geometry and voltage dependence of threshold voltage and for the subthreshold behavior of short-channel MOSFETs. Our approach uses conformal mapping techniques to analytically solve the two-dimensional Poisson equation, whereby inhomogeneous substrate doping is taken into account. The presented model consists of analytical equations in closed form and uses only physically meaningful parameters. Therefore, the results are not only useful in circuit simulators but also in calculations of scaling behavior, where planned processes can be investigated. Comparison with numerical device simulation results and measurements confirm the high accuracy of the presented model.     

A compact LDD MOSFET I-V model based on nonpinned surface potential

Based on nonpinned surface potential concept, in this paper we present a compact single-piece and complete I-V model for submicron lightly-doped drain (LDD) MOSFETs. The physics-based and analytical model was developed using the drift-diffusion equation and based on the quasi two-dimensional (2-D) Poisson equation. The important short-channel device features: drain-induced-barrier-lowering (DIBL), channel-length modulation (CLM), velocity saturation, and the parasitic series source and drain resistances have been included in the model in a physically consistent manner. In this model, the LDD region is treated as a bias-dependent series resistance, and the drain-voltage drop across the LDD region has been considered in modeling the DIBL effect. This model is smoothly-continuous, valid in all regions of operation and suitable for efficient circuit simulation. The accuracy of the model has been checked by comparing the calculated drain current, conductance and transconductance with the experimental data     

Electro-thermal analysis and optimization of edge termination of power diode supported by 2D numerical modeling and simulation

High reliability and performance of power semiconductor devices depend on an optimized design based on a good understanding of their electro-thermal behavior and of the influence of parasitic components on their operation. This leads to the need for electro-thermal 2/3-D numerical modeling and simulation in power electronics as an efficient tool for analysis and optimization of device structure design and identification of critical regions. In this paper we present an analysis and geometry optimization of a high power pin diode structure supported by advanced 2-D mixed mode electro-thermal device and circuit simulation. Lowering of the operation temperature by better power management and heat dissipation due to an optimized structure design will allow withstanding higher current pulses and suppressing the damage of the analyzed structure by thermal breakdown.