The use of an adaptive notch filter (ANF) is one of the most popular methods to block harmonics in a phase-locked loop (PLL). Existing ANFs suffer from drawbacks such as a low harmonic rejection capability, complex structure or instability. To improve the performance of ANF-based PLLs, an enhanced ANF (EANF) is proposed in this paper. Its structure, filtering characteristics and frequency-adaptive method are analyzed. Multiple EANFs can be easily cascaded and achieve adaptation through a common frequency feedback loop (FFL). A small signal model is provided, and its control parameters are tuned through the symmetrical optimum method. The harmonic rejection capability and stability of the proposed method are confirmed through simulation and experimental results.

中文翻译：

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一种准确而稳健的自适应陷波滤波器锁相环

使用自适应陷波滤波器 (ANF) 是阻止锁相环 (PLL) 中谐波的最流行方法之一。现有的 ANF 存在谐波抑制能力低、结构复杂或不稳定等缺点。为了提高基于 ANF 的 PLL 的性能，本文提出了一种增强型 ANF (EANF)。分析了其结构、滤波特性和频率自适应方法。多个 EANF 可以轻松级联并通过公共频率反馈回路 (FFL) 实现自适应。提供了一个小信号模型，其控制参数通过对称优化方法进行调整。通过仿真和实验结果证实了所提出方法的谐波抑制能力和稳定性。