Digital predistortion of power amplifiers using look-up table method with memory effects for LTE wireless systems

Ruchi Singla,Sanjay Sharma

doi:10.1186/1687-1499-2012-330

Abstract

Abstract Digital predistortion (DPD) techniques are widely used to linearize of RF power amplifiers. In this article, a memory polynomial-based power has been modeled with memory order of 5 and nonlinearity order of 9. These specifications had been found suitable for advanced long-term evolution (LTE) wireless systems. A suitable DPD model was created based on the least square error minimization. Results for the complementary cumulative distribution function and normalized mean squared error were also computed. The adjacent channel leakage power ratio and error vector magnitude calculations showed that the proposed DPD for LTE system performed within the required limits as desired.

Highlights

Wideband signals such as those used in long-term evolution (LTE) systems are spectrally more efficient
Complementary cumulative distribution function (CCDF) measurements provide important information for engineers involved in the design and manufacturing of system components used in fourth generation (4G) networks. 4G networks use OFDM that results in higher quality voice as well as greater data rates for cellular services
As engineers migrate to the advanced wireless communication systems such as LTE-advanced or 802.11ac, choosing and designing the right power amplifiers (PAs) to meet design goals at the lowest possible cost becomes more difficult, both for base stations and mobile devices

Summary

Introduction

Wideband signals such as those used in long-term evolution (LTE) systems are spectrally more efficient. The most important algorithm for models with memory for DPD implementation is Volterra series and its derivatives. Proposed model for DPD in LTE systems In the DPD architecture, x(n) is the input signal to the predistortion unit, whose output z(n) feeds the PA to produce output y(n). The DPD is described by a memory polynomial akq xðn–qÞjxðn–qÞj k1⁄41 q1⁄40 where the x(n) and z(n) are complex input signal and output signal of DPD model, respectively.

Results

Conclusion