New Trends for the Nonlinear Measurement and Modeling of High-Power RF Transistors and Amplifiers With Memory Effects

Abstract—Power amplifier (PA) behavior is inextricably linked to the characteristics of the transistors underlying the PA design. All transistors exhibit some degree of memory effects, which must therefore be taken into account in the modeling and design of these PAs. In this paper, we will present new trends for the characteri-zation, device modeling, and behavioral modeling of power tran-sistors and amplifiers with strong memory effects. First the impact of thermal and electrical memory effects upon the performance of a transistor will be revealed by comparing continuous wave and pulsed RF large-signal measurements. Pulsed-RF load–pull from the proper hot bias condition yields a more realistic representa-tion of the peak power response of transistors excited with modu-lated signals with high peak-to-average power ratio. Next, an ad-vanced device modeling method based on large-signal data from a modern nonlinear vector network analyzer instrument, coupled with modeling approaches based on advanced artificial neural net-work technology, will be presented. This approach enables the gen-eration of accurate and robust time-domain nonlinear simulation models of modern transistors that exhibit significant memory ef-fects. Finally an extension of the X-parameter (X-parameter is a trademark of Agilent Technologies Inc.) behavioral model to ac-count for model memory effects of RF and microwave components will be presented. The approach can be used to model hard non-linear behavior and long-term memory effects and is valid for all possible modulation formats for all possible peak-to-average ratios and for a wide range of modulation bandwidths. Both the device and behavioral models have been validated by measurements and are implemented in a commercial nonlinear circuit simulator. Index Terms—Behavioral model, device modeling, large-signal RF measurements, memory effects. I