Multicommodity flow models, failure propagation, and reliable lossnetwork design

Multicommodity flow (MF) models are well known and have been widely used in the design of packet-switched networks. They have also been used as approximations in the design of circuit-switched networks with reliability constraints. We investigate the usefulness of multicommodity models both as routing models and as an integral part of design models conceived under the failure propagation strategy. First, we compare the performance measures calculated by the models with results produced by a real-time technique. Next, we study the performance of networks dimensioned with flow models and with known adaptive models under failures of transmission facilities when a real-time routing technique is used. Results obtained using realistic data show that the MF models compare favorably with exact dimensioning algorithms when failures are considered     

Higher order models for computer-aided circuit design

A method is presented for converting a multiple- lump transistor physical model into a combination of first-order electrical models. This conversion technique allows any higher order physical model to be implemented with the present CACD programs.     

GaAs MESFET physical models for process-oriented design

A detailed physical model which is used to accurately predict the DC and microwave performance of GaAs MESFETs is described. This model, which accounts for hot electron effects in submicron FETs, includes trapping phenomena and heating due to power dissipation. It is used to determine the optimal design for small-signal and power devices, including single- and double-recessed FETs. The spread in device characteristics can be directly related to the variation in device geometry and process parameters experienced in fabrication. The accuracy and flexibility of this approach are demonstrated by comparison with measured data for a variety of devices     

Small-signal MOSFET models for analog circuit design

Presents first-order large-signal MOSFET models and derives corresponding small-signal models. The parameters of the small-signal models are related to operating-point bias and to the parameters of the IC process used to fabricate the device. The impact upon small-signal performance of many second-order effects present in small-geometry MOSFETs is explored. A representative analog circuit, fabricated with a 1 /spl mu/m feature-size NMOS technology, is analyzed using the small-signal models derived. Results of approximate analysis, without the use of computer aids, are compared with detailed computer simulation results.     

Discrete-time battery models for system-level low-power design

For portable applications, long battery lifetime is the ultimate design goal. Therefore, the availability of battery and voltage converter models providing accurate estimates of battery lifetime is key for system-level low-power design frameworks. In this paper, we introduce a discrete-time model for the complete power supply subsystem that closely approximates the behavior of its circuit-level continuous-time counterpart. The model is abstract and efficient enough to enable event-driven simulation of digital systems described at a very high level of abstraction and that includes, among their components, also the power supply. The model gives the designer the possibility of estimating battery lifetime during system-level design exploration, as shown by the results we have collected on meaningful case studies. In addition, it is flexible and it can thus be employed for different battery chemistries     

Land clutter models for radar design and analysis

Land clutter reflectivity has been described in the literature for many types of terrain, viewed by radars of different frequencies at different grazing angles. Significant gaps remain in the published data, especially for ground-based radars viewing the terrain at grazing incidence, and for bistatic situations where one path is at grazing incidence. An analytical model is proposed here which predicts many of the observed trends in data, as functions of range, antenna height, terrain roughness, and radar wavelength. By comparing measured data to the model, better correlations among data sets taken under different conditions can be obtained, and better understanding of the underlying propagation and scattering phenomena achieved.     

Multilevel metal capacitance models for CAD design synthesissystems

An empirical model for multilevel interconnect capacitance is presented. This is the first model that allows designers to compute capacitances of arbitrary complex metal geometries. Such flexibility is achieved by a novel strategy of constructing complex geometries from simple primitive cells. Agreement with accurate simulations and measurements is within 8% over an extensive range of dimensions     

Comparison of nonlinear MESFET models for wideband circuit design

The Curtice quadratic, Materka, Statz, and Rodriguez nonlinear models are compared from DC, CV, and RF points of view, to determine which is the most suitable for nonlinear wideband circuit design. For this comparison, GaAs MESFETs of various sizes are employed. These include devices of varying gate widths, gate lengths, number of fingers, and pinch-off voltages     

Material failure mechanisms and damage models

This work introduces a tutorial series on material failure mechanisms and damage models to familiarize nonspecialists with the fundamentals of failure mechanisms in engineering assemblies. Since failure is a complicated concept, four simple conceptual models for failure are discussed: stress-strength, damage-endurance, challenge-response, and tolerance-requirement. The specific failure mechanisms depend on material or structural defects, damage induced during manufacture and assembly, and on conditions during storage and field use. Conditions that affect the state of an item are broadly termed stresses (loads), e.g., mechanical stress and strain, electrical current and voltage, temperature, humidity, chemical environment, and radiation. The effects of stresses are influenced by geometry, constitutive and damage properties of the materials, manufacturing parameters, and the application environment     

一种可配置的老化预测传感器设计

随着工艺尺寸的缩减,老化导致的电路不稳定现象越来越严重。由于NBTI效应造成的老化是渐进的,因此老化是可预测的。由此提出了一种具有可配置延迟单元的老化预测电路,并将其中的稳定性校验器和锁存器的功能进行了整合。在老化的不同时期,针对老化程度,动态调节延迟单元的延迟大小,得到不同的保护带宽度,从而提高老化预测的准确率。并通过反馈电路达到对稳定性校验器的输出进行锁存的目的。与经典结构相比,电路在面积上平均节省20.6%左右,在功耗方面减少36%左右。Spice模拟器的仿真结果证实了电路的优越性。     

Validation of compact models of microcantilever actuators for RF-MEMS design

Electromechanical behavior of microcantilever specimens for in-plane and out-of-plane bending tests, currently designed by industry for Radio-Frequency application, are here analyzed. Main features of these two layouts are discussed. In particular, a comprehensive experimental validation of 2D and 3D numerical models implemented to predict the coupled electromechanical behavior of these microsystems is performed. Effectiveness of plane models to predict pull-in, in presence of geometric non-linearity, due to large tip displacement and initial curvature of microbeam, is investigated. Three dimensional models are then used to investigate the local effects of the electric field and the limits of the two dimensional approach. In addition, this paper investigates the effectiveness of 2D models to be used as compact numerical tools in substitution of some known Model Order Reduction techniques, which unfortunately are unsuitable to predict simultaneously the effects of both the electromechanical and geometric non-linearities.     

Consistent noise models for analysis and design of CMOS circuits

Simple, physics-based MOSFET noise models, valid over the linear, saturation, and subthreshold operation regions are presented. The consistency of the models representing series-parallel associations of transistors is verified. Simple formulas for hand analysis using the inversion level concept are developed. The proportionality between the flicker noise corner frequency and the transistor transition frequency is proved and experimentally verified under wide bias conditions. Application of the noise models to a low-noise design is shown.     

A comparison of IGBT models for use in circuit design

In choosing an accurate insulated gate bipolar transistor (IGBT) model for power electronic circuit design, physics-based models are frequently preferred due to their high accuracy and fast simulation speed in comparison to other types of models. In this paper, an experimental comparison of two such models is made, using parameters extracted from experimental measurements. The comparison focuses on two particular IGBTs-the BUP202 and the BUK854-representing the two common types of IGBT, respectively, the nonpunchthrough and the punchthrough IGBT. The models are investigated for the IGBT's operation in three situations typical of low-power (600 V, 10 A) applications     

Equivalent circuit models for computer aided design of microstriprectangular structures

Microstrip rectangular structures are modeled in terms of equivalent circuits in order to overcome many of the drawbacks and limitations of previously proposed approaches and the poor accuracy still introduced by most of the presently available models. Through a successful electromagnetic approach, lumped element models for interacting and noninteracting step discontinuities have been created and tested. An alternative model is also proposed to account for shunt connected double and single stubs in cross and tee junction with the main line, respectively. The different models have been tested on the same structure to demonstrate their congruency     

The design error contribution to failure

This paper describes a practical approach to improving the reliability of electronic equipment. Recognizing that unreliable, untestable and unmaintainable equipment can be built with high grade reliable components, several approaches are suggested to improve designer performance. Methods include education programs, communication improvements, checklists, design handbooks and design review methods.