INSTITUTE OF ELECTRICAL AND ELECTRONIC ENGINEERS

WAVES AND DEVICES

PHOENIX CHAPTER

January 11, 2007 MTTS Meeting

www.eas.asu.edu/~wadweb

Global Stability Analysis and Stabilization of Power Amplifiers

Professor Almudena Suarez

Electronics Department, University of Cantabria, Santander, Spain

Abstract

Power amplifiers often exhibit instabilities giving rise to frequency division by two or oscillations at incommensurate frequencies. These phenomena, observed from a certain level of input power, cannot be detected through a small-signal stability analysis of the circuit. Instead, a large-signal stability analysis must be performed. The talk introduces the local and global stability concepts and the analysis techniques, based on harmonic balance. Different approaches for the local-stability analysis of nonlinear regimes will be presented, with emphasis on the pole-zero identification. Techniques will be shown for the detection of the most common types of bifurcations in power amplifiers. The final goal will be the stabilization of the circuit and the design corrections in order to suppress the undesired phenomena will also be presented.

For illustration, the simulation tools will be applied to two different switching amplifiers: the first amplifier is a Class-E/F amplifier, which showed oscillations, hysteresis and chaos; the second amplifier is a Class-E amplifier, which showed jumps in the power-transfer curve and sideband noise amplification. After the application of the different techniques, the two amplifiers were globally stabilized for all the expected operating values of the amplifier bias voltage and input power. This was achieved with negligible degradation of the amplifier performance, in terms of output power and drain efficiency. The stable behaviour obtained in simulation was experimentally confirmed.

Biography

Almudena Suárez received the Electronic Physics degree and Ph.D. degree from the University of Cantabria, Spain, in 1987 and 1992, respectively, and the Ph.D. degree in electronics from the University of Limoges, France, in 1993. In 1987, she joined the Electronics Department, University of Cantabria. From May 1990 to December 1992, she was on leave with the Institute de Recherche en Communications Optiques et Microondes (IRCOM), University of Limoges. Since 1993, she has been an Associate Professor with the University of Cantabria, where she is a member of the Communications Engineering Department. She coauthored Stability Analysis of Microwave Circuits (Artech House, 2003). Her research interests include the nonlinear design of microwave circuits, especially the nonlinear stability and phase-noise analysis and investigation of chaotic regimes. Dr. Suárez is a Distinguished Microwave Lecturer of the IEEE Microwave Theory and Techniques Society (2006–2008).

Date: Thursday January 11, 2007

Location: Group Conference Rm, Bldg 94, Freescale Semiconductor, 2100 E. Elliot Rd., Tempe, AZ

Use Freescale Main Entrance (South) facing Elliot Road

Time: 5:00 - 6:00pm Presentation

For more information, please call Chuck Weitzel (Chapter Chair) at (480) 413-5906.