Adaptive HPA Linearization Technique for Practical ATSC DTV System

Abstract

In the digital television (DTV) broadcasting system, high power amplifier (HPA) is the most essential device to expand the service availability and coverage. However, as the input power level of HPA increases, the HPA is driven into the saturation mode and HPA output signal suffers nonlinear distortion. HPA nonlinearity is potentially responsible for adjacent channel interference and inter-symbol interference (ISI). To prevent these negative effects, digital pre-distortion (DPD) is one of the most widely used techniques for the HPA linearization. In order to estimate the HPA nonlinearity, DPD technique requires a feedback signal, which needs to be appropriately down converted and digitized from HPA output. However, since the feedback signal might be generally influenced by offset error, it is important to reduce the offset error in order to improve HPA linearization. In this paper, an adaptive DPD technique based on iterative look-up table (LUT) update and adaptive acquisition is proposed. The proposed DPD technique is validated on the advanced television systems committee (ATSC) terrestrial DTV broadcasting system by computer simulation and laboratory test.