Design-Oriented Analysis and Practical Applications of Log-Domain Filtering

即使在日益数字化的今天，模拟连续时间电路在许多应用中也是必需的。目前的模拟处理方法遇到了根本的限制。对数域滤波是一种相对较新的方法，它使用简单的低压电路提供宽动态范围和出色的高频响应。对数域滤波器利用双极型晶体管或弱反转MOSFET的跨线性电流-电压特性来实现整体线性。基本信号处理元件的形式可以相当简单，并且它们的高频性能可以很好，而失真可以很低，因为大多数晶体管非线性在电路中被消除。这项研究有三个主要推动力：第一个推力是对数域电路的基本的、面向设计的分析。对数域过滤器的局限性的设计方法和基本理解还处于早期阶段。基本分析允许开发用于评估和比较对数域电路的品质因数。第二个重点是开发新的对数域电路拓扑。基于对基本限制的理解，正在设计新的电路以提高性能。第三个推力是对数域电路的应用。集成电路正在建造和测试中，以证明对数域电路在实际应用中的有效性。最初的重点是两个应用领域：低压无线通信，以开发对数域电路的性能潜力，以及自适应和生物启发电路，以建立其基本的简单性。

Even in today's increasingly digital world, analog continuous time circuits are needed in many applications. Current approaches to analog processing are running up against fundamental limitations. Log-domain filtering is a relatively new approach that offers wide dynamic range and excellent high-frequency response using simple, low-voltage circuits. Log-domain filters exploit the translinear current-voltage characteristics of bipolar transistors or weak-inversion MOSFETS to achieve overall linearity. The basic signal processing elements can be quite simple in form and their high-frequency performance can be excellent while distortion can be low because most of the transistor non-linearities are cancelled within the circuit. This research has three major thrusts: The first thrust is toward fundamental, design-oriented analysis of log-domain circuits. Design methodologies and fundamental understanding of the limitations of log-domain filters are in an early stage. Fundamental analyses allow development of figures of merit for evaluating and comparing log-domain circuits. The second thrust focuses on developing new log-domain circuit topologies. Based on an understanding of fundamental limitations, new circuits are being designed to improve performance. The third thrust is toward applications of log-domain circuits. Integrated circuits are being built and tested to demonstrate the usefulness of log-domain circuits in practical applications. Initial focus is on two application areas: low-voltage wireless communications, to exploit the performance potential of log- domain circuits and adaptive and biologically inspired circuits, to build on their fundamental simplicity.