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

即使在当今日益数字化的世界中，许多应用仍然需要模拟连续时间电路。目前的模拟处理方法遇到了基本的限制。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晶体管或弱反转mosfet的非线性电流电压特性来实现整体线性。基本的信号处理元件可以在形式上非常简单，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抵消了。本研究有三个主要方向：第一个方向是对对数域电路进行基本的、面向设计的分析。设计方法和对对数域滤波器局限性的基本理解还处于早期阶段。基础分析允许发展的价值数字，以评估和比较对数域电路。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，人们正在设计新的电路来提高性能。第三个方向是对数域电路的应用。集成电路正在建造和测试，以证明对数域电路在实际应用中的有用性。最初的重点是两个应用领域：低压无线通信，以开发对数域电路和自适应和生物启发电路的性能潜力，建立在他们的基本简单性。

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.