Analog CMOS Realizations of IIR Adaptive Filters

为了实现最近开发的无限脉冲响应(IIR)自适应滤波器，人们正在开发连续时间模拟CMOS电路。这些结构都是基于陷波双二次结构，具有良好的灵敏度特性，在保证滤波器稳定的同时易于调整。以往的研究主要集中在对这些结构的理论分析上，证明了这些结构的全局收敛，并且证明了这些结构具有很小的偏差。未来的研究将集中在实际应用的自适应滤波器的开发上。这些包括调频解调器、频率辅助锁相环和科斯塔斯环路、载波和时钟提取电路、用于频谱分析的高效信道组和周期性噪声消除电路，仅举几例。在许多方面，这些新电路代表了锁相环到多正弦情况的推广。因此，它们将是有史以来第一个能够实时地将具有未知频率的单个正弦信号从多正弦输入信号中分离出来的模拟电路。

Continuous-time analog CMOS circuits are being developed to realize infinite-impulse-response (IIR) adaptive filters that were recently developed. These structures are all based on notch biquads that have good sensitivity properties and are easy to adapt while guaranteeing that the filter is stable. Previous research has concentrated on the theoretical analysis of these structure, where global convergence was proved and it was shown the structures have very small biases. he future research will focus on the development of the adaptive filters for practical applications. These include FM demodulators, frequency- assisted phase-locked-loops and Costas-loops, carrier and clock- extraction circuits, efficient channel-banks for spectral analysis and periodic noise cancellation circuits, to name only a few. In many ways, these new circuits represent a generalization of the phase-locked-loop to the multi-sinusoidal case. As such, they will be the first ever analog circuits capable of isolating individual sinusoids having unknown frequencies from a multisinusoidal input signal, in real- time.