Module 1: Digital Predistortion of Power Amplifiers

but is no longer kept current and may contain obsolete or inaccurate references. We regret any inconvenience this may cause. For the latest information on Agilent's line of EEsof electronic design automation (EDA) products and services, please go to: Active linearization has become an important technology in modern communications systems. The emphasizes on higher data rates and spectral efficiency has driven the industry towards linear modulation techniques such as QPSK, 64 QAM, or multicarrier configurations. The result is a signal with a fluctuating envelope which generates intermodulation (IM) distortion from the power amplifiers. Since most of the IM power appears as interference in adjacent channels, it is important to use a highly linear power amplifier. Linearization of a power-efficient amplifier is a desirable alternative to backing-off a Class A amplifier which would result in low power efficiency as well as considerable heat dissipation. A digital baseband predistorter has the distinct advantage of being capable of handling rapid fluctuations in amplifier characteristics, however it typically operates on low bandwidth signals. This predistortion technique can function independently from the modulation scheme. worked on a wide variety of projects including: multi-rate digital signal processing, RF/Microwave communications systems, and Adaptive Array Antennas. While at Simon Fraser University he developed a number of Adaptive Linearization techniques ranging from Feedforward, Active Biasing, Work Function Predistortion to Digital Baseband Predistorters. He has published numerous technical papers on Linearization and has given many presentations at various companies on the subject. He continues to research the field of utilizing DSP techniques to produce Power Efficient Amplifiers for Mobile Communications applications.. You will receive an introduction and basic overview of the key features, technologies, and performance requirements of Predistortion in this paper. Solutions for solving some of the design challenges will also be presented. An adaptive digital baseband predistorter is demonstrated using the ADS. More in depth analysis can be obtained in the references at the end of this technical information session. – – due to fluctuating envelope: QPSK, 64 QAM, etc. due to fluctuating envelope: QPSK, 64 QAM, etc. • • Two methods of achieving linear amplification: Two methods of achieving linear amplification: – – Back-off the Class A amplifier-this reduces the power Back-off the Class A amplifier-this reduces the power efficiency and increases the heat dissipation. efficiency and increases the heat dissipation. – – Linearize a power-efficient amplifier using external circuitry. Linearize a power-efficient amplifier using external circuitry. …