Q. Cai

Integrated physics-oriented statistical modeling, simulation, and optimization (MESFETs)

Physics-based modeling of MESFETs is addressed from the point of view of efficient simulation, accurate behavior prediction and robust parameter extraction. A novel integration of a large-signal physics-based model into the harmonic balance equations for simulation of nonlinear circuits, involving an efficient Newton update, is presented and exploited in a gradient-based FAST (feasible adjoint sensitivity technique) circuit optimization technique. For yield-driven MMIC design a relevant physics-based statistical modeling methodology is presented. Quadratic approximation of responses and gradients suitable for yield optimization is discussed. The authors verify their theoretical contributions and exemplify their computational results using built-in and user-programmable modeling capabilities of the CAE systems OSA90/hope and HarPE. Results of device modeling using a field-theoretic nonlinear device simulator are reported. >

Integrated harmonic balance and electromagnetic optimization with geometry capture

This paper presents an integrated approach to nonlinear circuit optimization. Electromagnetic simulations are seamlessly integrated into harmonic balance simulation and optimization. For the first time, complicated planar structures can be made fully optimizable through the parameterization process of this geometry capture technique. They are then treated as individual elements in electromagnetic simulations and are embedded into the overall nonlinear circuit to be optimized. A comprehensive class B frequency doubler design demonstrates our approach.<<ETX>>

Nonlinear circuit optimization with dynamically integrated physical and device models

The approach used, which is directed at the next-generation tools for yield optimization, dynamically integrates physics-based device models. The FET model of M.A. Khatibzadeh and R.J. Trew (IEEE Trans. Microwave Theory Tech., vol.36, p.231-8, 1988) is treated in a novel formulation of harmonic balance simulation. Adjoint sensitivity analysis allows efficient optimization of parameters such as device dimensions, material-related parameters, doping profile, channel thickness, etc. Parameter extraction extraction and power amplifier design are demonstrated.<<ETX>>

A novel approach to statistical modeling using cumulative probability distribution fitting

A novel approach to statistical modeling is presented. The statistical model is directly extracted by fitting the cumulative probability distributions (CPDs) of the model responses to those of the measured data. This new technique is based on a solid mathematical foundation and, therefore, should prove more reliable and robust than the existing methods. The approach is illustrated by statistical MESFET modeling based on a physics-oriented model which combines the modified Khatibzadeh and Trew model and the Ladbrooke model (KTL). The approach is compared with the established parameter extraction/postprocessing approach (PEP) in the context of yield verification.<<ETX>>

Physics-Based Design and Yield Optimization of MMICs

This paper addresses physics-based design and yield optimization of MMICs. Multidimensional statistical models are considered for the physical, geometrical and process-related parameters of active and passive devices. An efficient gradient-based yield optimization technique is employed. The yield of an X-band amplifier is improved from 47.5% to 78.5%.

Predictable yield-driven circuit optimization

The authors present a comprehensive approach to predictable yield optimization. They utilize a new physics-based statistical GaAs MESFET model which combines the advantages of the DC Khatibzadeh and Trew model and the small-signal Ladbrooke formulas. The yield of a broadband amplifier was significantly improved after optimization. Predicted yield over a range of specifications was verified by device data. The benefits of simultaneous circuit-device yield optimization assisted by yield sensitivity analysis are demonstrated.<<ETX>>

Compression analysis of a high power BJT amplifier

In this paper we present the compression analysis of a BJT high power amplifier circuit. This circuit was chosen by Microwave Engineering Europe (MEE) as a challenge to CAD programs. The bipolar transistor is modeled by a SPICE model. Extraction of the model parameters was performed by fitting the model responses to vendor-published S-parameter data. In addition to compression analysis of the amplifier, we carried out Monte Carlo statistical simulation and sensitivity analysis. All simulations and optimizations were performed by our CAD software system OSA90/hope, in particular by our nonlinear harmonic balance simulator.

Heterogeneous parallel yield-driven electromagnetic CAD

Within an integrated parallel optimization framework, we are able, for the first time, to apply electromagnetic (EM) optimization to the yield-driven design of microstrip circuits of arbitrary geometries. Parallel optimization handles the massive demand on computer resources, due to the large number of designable parameters describing an arbitrary geometry and the large number of simulations involved in yield optimization. Our parallel strategy can be implemented over local and wide area networks supporting heterogeneous workstations.<<ETX>>

Cost-driven physics-based large-signal simultaneous device and circuit design

We present a cost-driven approach to the emerging demand for simultaneous device and circuit design. Here, an analytic physics-based Raytheon model facilitates fast large-signal simulation and optimization. A novel one-sided Huber approach is applied to design centering. The problem of cost-driven design is formulated as the minimization of the cost function while maintaining the required yield. Devices and matching circuits are optimized simultaneously, the advantages of which are demonstrated by a single-stage power amplifier design.<<ETX>>