RF power amplifier's nonlinear modelling with memory effect

Abstract

Theoretically, memoryless nonlinear effect is the main concern for RF power amplifier (PA) modelling and analysis. However, the latest generation wireless communication systems, such as Wi-Fi, WiMAX and LTE, using wider bandwidth, add new problems for the analysis of RF PAs, which is the memory effect associated with the bandwidth. The memory effect causes additional distortion to the PA and affects the performance of digital predistortion (DPD) design. Previously, we predicted the memoryless spectrum regrowth of a PA related to its intercept points up to arbitrary high order for a few of wireless communication signals, such as TDMA, CMDA and OFDM. In this letter, we propose a simplified Hammerstein structure-based method to consider the memory effect as well in order to analyse the nonlinear characteristic of PAs more precisely and completely. The simplification greatly reduced the complexity of classic Hammerstein system identification for PAs. The result will be useful in the analysis of RF PAs with memory effect and the proposed PA model is intended to be used in predistorter design for modern wideband wireless communication systems.