Combiner synthesis for active load-modulationbased power amplifiers

Abstract

This chapter discusses the fundamental operation of Doherty and outphasing Pas. Rather than using the original combiner topologies as a starting point, our focus will be on the desired transistor operation. Based on the active loadmodulation conditions that the Doherty and outphasing Pas dictate, we will therefore instead derive the combiners that present the desired behavior. The original solutions will thus appear as special cases when ideal operation is assumed. For any other case, new solutions will appear. We will show how this approach can give both new insights, extended design spaces and improved performance. In the first part of this chapter, we will establish a theoretical framework for Doherty and outphasing combiner synthesis from the conditions that guarantee efficient operation. This will thereafter be applied and practically demonstrated, first in a Doherty design context and then in an outphasing design context. The chapter will be concluded with a brief summary and suggestions for future work.