高阶QAM实时多域测试多模式自适应盲均衡技术研究

提出了一种全新的宽带通信信号实时多域分析通用架构,详细介绍了该架构下信号分析的基本原理。在这种架构的基础上,通过加载不同的算法,不仅能够实现各种宽带通信信号高精度实时宽带频谱分析,而且还能同时实现宽带通信信号时域、调制域等多域联合分析。针对宽带高阶正交幅度调制（QAM）通信信号实时多域分析,详细讨论了面向测试的基于GMMA和DDLMS双模自适应盲均衡算法。系统仿真结果证明：相比GMMA自适应盲均衡算法,双模自适应盲均衡算法收敛速度明显提高,256QAM信号均衡后输出残余码间串扰（ISI）改善提高了10dB;同时通过实验验证,采用20MHz实时分析带宽对码率为6.4MSps的宽带256QAM信号进行实时多域分析,误差矢量幅度（error vectorm agnitude,EVM）测试误差小于2%。

Adaptive blind equalization algorithm with multi-module for high-order QAM real-time multi-domain measurement

Based on real-time multi-domain signal analysis frame for high-order quadrature amplitude modulation （QAM） communication, a novel adaptive blind equalization algorithm for high-order QAM real-time multi-domain analysis and specifications measurement is presented. The proposed algorithm consists of the generalized multi-modulus algorithm （GMMA） for initial convergence during blind startup, and the decision-directed least mean square algorithm （DDLMS） which is used to enhance the performance. The two operation modules are automatically switched according to the equalizer output error level. Combined with step-size parameter variation online in each module, the blind equalization solution can converge rapidly with low residual tap fluctuation noise. The simulation results show that the proposed technique converges quickly and reduce the inter-symbol interference （ISI） caused by the propagation channel to -43 dB, with about 10 dB improvement contrast to the GMMA for 256QAM. On the other hand, the proposed algorithm is practically implemented in the communication testing system. The measurement error of EVM is less than 2% for 6.4 MSps 256QAM in the 20 MHz real-time analysis bandwidth. For these considerable merits, the scheme is quite suitable for high-resolution communication measurement instruments design.