Workshop: WSUN2

"RF Power Transistor and Amplifier Characterization Techniques"

Sunday 7 Jan., 2007
1:30- 5:30 PM

Abstract:
The accurate measurement of the electrical performance of high power RF transistors and power amplifiers presents a number of challenges.  The characterization of power transistors for applications in classic reduced conduction angle amplifier modes has for many years been performed by load-pull techniques. And yet as the power density of the transistors increases in response to the absolute power demands of wireless infrastructure amplifier applications, we are faced with significant challenges in maintaining the accuracy of load-pull measurements that are being made close to the edge of the Smith Chart using passive tuners.  This challenge has been met with better measurement techniques, as well as the development of a variety of active load-pull techniques.  Further, the new capability for making vector-corrected measurements at high powers, using large-signal network analysis methods, has enabled the study and understanding of the nonlinear behavior of the transistor at high powers.  The coupling of the large-signal network analyzer with harmonic load-pull techniques has enabled us to control the impedance environment seen by the transistor, and has led to the practical identification and realization of high-efficiency amplifier modes such as Classes E & F, for example.  These high efficiency amplifier modes are generally very nonlinear, and linearization or pre-distortion techniques need to be applied.  This has resulted in the parallel development of measurement systems of high linearity, bandwidth and dynamic range, for the characterization of linearization techniques in these high power applications.

In this workshop we will highlight the measurement challenges and their solutions in the world of high power RF device and amplifier design, as found in wireless communications base stations, for example. The workshop will cover topics including passive and active load-pull techniques, harmonic terminations, large-signal network analysis, and linearity measurements.  The level of the discussion will be appropriate for the newcomer to high power RF transistor and amplifier characterization, as well as seasoned professionals who wish to survey the broad perspective of the available measurement techniques, new and old.  Speakers have been drawn from a number of universities who are in the forefront of technological leadership in high power RF device and amplifier characterization.  The presentations will cover a range of techniques for characterization, evaluation and verification of high power RF transistors and power amplifiers. We shall also have a short panel session at the end of the workshop, with all presenters in attendance.

Organizers:

Dr John Wood and Mr Basim Noori
Freescale Semiconductor, Inc., RF Division, Tempe, AZ

Speakers:

• Basim Noori, Freescale Semiconductor
  "Load-Pull measurement accuracy under realistic high power conditions"

• Andrea Ferrero, Politecnico di Torino
  "Active, closed-loop, harmonic load- and source-pull systems"
  

• Johannes Benedikt, University of Cardiff
  "High power active load pull measurements of RF power transistors"

• Jan Verspecht, Jan Verspecht bvba
  "Affordable LSNA Technology"

• Paul Tasker, University of Cardiff
  "Envelope load-pull system"
  

• Michael LeFevre, Freescale Semiconductor
  "Digital Pre-Distortion characterization system for RF PA evaluation"

• Peter Asbeck and Don Kimball, UC San Diego
  "Evaluation of RF power transistors in Drain Modulation"