Circuits Optimization and System Linearization for High Efficiency and Wideband Envelope Tracking Architecture
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摘要:
为改善包络跟踪(ET)发射机带宽、效率、线性度等指标,需优化其关键电路性能并校正系统非线性行为。针对该问题,该文构建电源调制器等效模型,推导其效率极值并阐述效率优化方法;引入频率补偿网络来提升电路带宽及线性性能;基于系统非线性行为特征,提出包络增强型数字预失真模型及线性化方案;设计实际电路并搭建包络跟踪系统。对于S频段5/10/20 MHz带宽6.7 dB峰均比测试信号,该系统功放平均效率分别为61%, 54%, 44%,且矢量幅度误差(EVM)均优于1%,具有较好的带宽、效率、线性度等性能,验证了电路优化方法及非线性行为校正方案的可行性。
Abstract:To improve bandwidth, efficiency and linearity of Envelope Tracking (ET) architecture, it is necessary to optimize the performance of envelope supply modulator and linearize nonlinear behavior of the ET system. The optimization procedure of the supply modulator is proposed based on the equivalent circuit model. The frequency compensation network is used to improve the bandwidth and linearity of the modulator circuit. An envelope enhanced memory polynomial digital pre-distortion model is introduced to address the nonlinear distortion of the ET system. The practical circuit mentioned above is fabricated and the overall experimental system is set up. Measurement results show that the ET PA at S-band obtains measured efficiency 61%, 54%, 44% and Error Vector Magnitude (EVM) 1% for 6.7 dB PAPR signals with 5 MHz/10 MHz/20 MHz modulation bandwidths, respectively. The ET system exhibits competitive bandwidth, efficiency and linearity, which verifies the proposed optimization and linearization methodology.
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表 1 本文EA电路测试结果与近年文献结果对比
表 2 ET系统测试结果
信号带宽(MHz) DPD 功率(dBm) 增益(dB) 效率(%) ACPR1(dBc) EVM(%) 5 无 34.4 11.0 61.3 -26.7 7.50 5 有 34.4 11.0 60.8 -49.7 0.32 10 无 34.6 11.1 56.7 -26.8 8.10 10 有 34.2 10.7 53.7 -46.3 0.60 20 无 34.3 11.3 46.4 -26.4 8.90 20 有 34.1 11.1 44.1 -46.0 0.67 -
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