Analog CMOS Realizations of IIR Adaptive Filters

连续时间模拟CMOS电路正在开发，以实现最近开发的无限脉冲响应（IIR）自适应滤波器。这些结构都是基于凹口biquads，具有良好的灵敏度特性，易于适应，同时保证了过滤器的稳定性。以前的研究主要集中在对这些结构的理论分析上，证明了全局收敛性，并表明结构具有非常小的偏差。未来的研究重点将是开发实际应用的自适应滤波器。其中包括调频解调器，频率辅助锁相环和costas环，载波和时钟提取电路，用于频谱分析的有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在多正弦情况下的推广。因此，它们将是有史以来第一个能够实时从多正弦输入信号中分离出频率未知的单个正弦波的模拟电路。

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.