卫星高速宽带自适应调制解调器算法与实现

本文研究了高速宽带自适应调制解调器系统中的载波同步、信噪比估计、帧同步检测、自适应门限等关键算法.提出了宽带自适应调制解调器的总体结构和硬件实现方案，改进了载波频偏恢复和高阶调制软判决解映射的传统硬件实现结构.对实现的原理样机进行了性能测试和分析.测试结果表明，该解调器可以在2～45 MS/s符号速率下自适应工作.基带环路误码率性能和中频环路性能与理论值之差分别小于0.2 dB和1 dB.对模拟的0.65 dB/s的卫星信道雨衰变化，系统链路自适应算法做到了实时有效跟踪和匹配. 

Design and Implementation of Wideband High-Speed Adaptive Coding and Modulation Modem

Adaptive broadband modem is achieved by that, the receiver signals the estimated channel quality via an available return channel to gateway to select the best modulation and coding scheme to adapt the channel change timely. In this paper, some key algorithms were studied for the adaptive broadband modem system, including the algorithm for carrier recovery, SNRs estimation, frame synchronization, and adaptive threshold switching. The architecture and hardware implementation schemes of the wideband adaptive coding and modulation demodulator were presented. The traditional hardware realization structure was improved for carrier frequency recovery and high-order modulations de-mapping based on soft decision. Performance of the implemented modem was tested and analyzed. The test results show that the prototype can work normally at symbol rates from 2 MS/s to 45 MS/s. The difference between the BER performance of base band loop and the theoretical limit is less than 0.2 dB, the difference between the BER performance of the intermediate frequency loop and the theoretical limit is less than 1 dB. The system link adaptive algorithm can track and match the imitative rain-field 0.65 dB/s channel attenuation well.