An Adaptive Equalizer to Reduce the Nonlinear Distortion Effects in Satellite Broadcasting Systems

Abstract

This article presents the BER performance improvements achieved when adopting Adaptive Equalization based on Decision Feedback Equalizer (DFE) to tackle the negative effects of nonlinear distortion in the receiver performance, caused by the Traveling Wave Tube Amplifier (TWTA), in a satellite receiver devoted to broadcasting. We have evaluated the performance for the DVB-S2 modulations, but the proposed DFE can be easily extended to be used in DVB-S2X systems. In our previous work we have presented the performance gains when using the same DFE to tackle the Inter-Symbol-Interference (ISI) caused by the Land Mobile Satellite Channel (LMSC). In that work, we have presented prototyping results in FPGA targeting a ASIC implementation. In this work we also investigate the performance improvements of the proposed DFE to tackle the effects of the nonlinearity combined with the ISI. The simulations results have shown that the proposed equalizer is capable of bringing significant performance improvements in both cases, i.e pure nonlinearity and nonlinearity combined with ISI, specially for the higher order modulation. It is worth mentioning that our proposal does not deal with the out-of-band spurious emissions caused by the nonlinear distortion, which needs to be handled by an appropriate technique such as predistortion.

On the performance improvements of digital satellite receivers in the presence of non-linear distortion and multipath channel using decision feedback

“…Proposed in [3], the author present promising results of a DFE working under DVB-S2 standard, showing that the DFE architecture can be used to meet DVB-S2 BER performance constraint under ISI, additionally in [12], the ability of the same architecture to mitigate in some degree NLD introduced by HPA is discussed, only by simulations means, also showing promising results. Therefore, those works encourage the further DFE study regarding the NLD mitigation capability, which will be discussed here more in depth, and a Volterra's filter equalizer will be exclusively implemented to be compared with the DFE.…”

“…For this work, is chosen the classical DFE structure with NLMS as adaptive algorithm, where the modeling and evaluation will be discussed in section 6.1, using several scenarios for its evaluation, each one with a distinguished evalutation goal. As in [8],…”

“…In [8], the authors propose the same structure in [3], now discussing it NLD mitigation capability, in simulations means, showing promising results using a more simple structure compared with [4], which is a more appropriate candidate to be implemented in ASIC.…”