Nonlinear amplifier effects in communications systems

Abstract

This paper introduces a figure-of-merit to inves- tigate tradeoffs between amplifiers and modulation waveforms in complex digital communications systems. Class-AB amplifiers are investigated with a variety of modulation schemes to better understand the relations between amplifier efficiency, amplifier distortion, signal in-band and adjacent channel interference, and power consumption. The goal is to better understand the tradeoffs needed to design low-energy communications systems. systems. Mobility and reasonable operating or talk times between battery charges are critical. These, in turn, require low weight and long battery life. Both can be improved with a more power-efficient system. This paper investigates the tradeoffs between modulation and amplifier nonlinearity and efficiency. The goal is to investigate the amplifier-modulation combination to minimize the energy required to communicate information. The paper is organized as follows. Section II introduces a useful figure-of- merit to quantify the energy requirements of different amplifier modulation combinations under different drive conditions. Section III describes the system models, including different modulations schemes, and the amplifier model being used. Section IV discusses the simulation procedures and results of the simulations. Finally, the paper is summarized in Section V.