Joint Seminar of the IEEE Ottawa MTT/AP, CPMT, CAS/EDS/SSCS Chapters and

Department of Electronics, Carleton University

Speaker: Dr. David Root

IEEE MTT Distinguished Microwave Lecturer

Agilent Technologies, Santa Rosa, California

Title: Nonlinear Analog Behavioral Modeling of Microwave Devices and Circuits

Time: 12:00-12:50pm (overview)

1:00-2:00pm (technical advances)

Monday March 31, 2008

Location: 4124 Mackenzie Engineering Building, Carleton University

Abstract: Modern microwave systems are designed in a top-down hierarchical process, with specifications starting at the system level, propagating down towards the subsystem, module, integrated circuit, and finally to the level of the transistor, resistor, and other fundamental electronic building blocks. A complimentary bottom-up process combines accurate representations of the building blocks at one level of abstraction to create or verify a functional block at the next higher level of design complexity. At a low level in the design hierarchy is the nonlinear device, or transistor. A detailed model, involving the simulation of the many coupled partial differential equations of physics is often needed to design such a device. However, one cannot simulate an entire IC at this physically detailed level. The complexity of the problem is overwhelming in terms of computer resources and time. Instead, for the purpose of integrated circuit design, transistor terminal (behavioral) characteristics can be abstracted into �compact� nonlinear models (SPICE models) and their interaction simulated at the circuit level. Analogously, modern communication systems are sufficiently complex to preclude their complete simulation at the compact transistor model level of description. There are simply too many nonlinear equations to solve to make this practical. Instead, the input-output behavior of the ICs can be abstracted into functional block behavioral models, and the simulations done at the next higher abstraction level. 

This lecture introduces general concepts and specific techniques for effective (efficient, general, and accurate) nonlinear behavioral modeling of microwave semiconductor devices and functional circuit blocks. A behavioral model is a simplified but accurate model of a lower-level component in the design hierarchy that simulates efficiently at the next higher level of abstraction. A unified treatment at both the device and functional block level is a distinguishing feature of this presentation. So too is the application to behavioral models constructed from real measurements and also from simulations starting from a detailed (complex) model. The emphasis is placed on the combination of nonlinearity and dynamics. Nonlinearity includes harmonic and inter-modulation distortion, clipping, etc. Dynamics includes frequency-dependence and long-term memory effects from a variety of physical origins. In the realm of dynamic nonlinearities, insight from linear analysis cannot always be applied. Superposition is not generally valid, the Fourier domain is less useful, and Green functions don�t exist. No fully general or overarching theories of nonlinear dynamical systems exist that are comparable to what exists for linear systems. Nevertheless, great progress has been made recently in nonlinear behavioral modeling. In fact, this lecture suggests we are at the threshold for full interoperability of large-signal measurement systems, modeling approaches, and simulation algorithms for nonlinear hierarchical behavioral modeling. This means we can begin to do for driven nonlinear microwave systems what small-signal S-parameters enable for linear systems.

Dr. David E. Root received B.S. degrees in physics and mathematics, and, in 1986, the Ph.D. degree in physics, all from MIT.

He joined the Hewlett-Packard Company (now Agilent Technologies, Inc.), in 1985, where he has held both technical and management positions since. He is presently Principal Research Scientist at Agilent’s High Frequency Technology Center in Santa Rosa. His current responsibilities include nonlinear behavioral and device modeling, large-signal simulation, and nonlinear measurements for new technical capabilities and business opportunities for Agilent.

David was a Visiting Scholar and Lecturer at the University of California at San Diego (UCSD) for the fall, 2005 quarter. He is Vice-Chair of the IEEE MTT-S Committee on CAD (MTT-1) and a member of the Technical Program Committee of the International Microwave Symposium. He is a reviewer for the IEEE Transactions on Microwave Theory and Techniques. He is co-editor of the recent book Fundamentals of Nonlinear Behavioral Modeling for RF and Microwave Design, Artech House, 2005. He was named 2006-2008 IEEE MTT-S “Distinguished Microwave Lecturer.” David was recently named the recipient of the 2007 IEEE ARFTG Technology Award. He is a Fellow of the IEEE.