Low-Power, Wide Dynamic Range Companding Analog Signal Processors

点击翻译按钮获取中文摘要

LOW-POWER, WIDE DYNAMIC RANGE COMPANDING ANALOG SIGNAL PROCESSORSY. Tsividis, Columbia UniversityABSTRACTThe context of this work is fully integrated systems involving a computer plus an analog signal processor. The latter is often a necessary part of the interface to the physical world in such fields as telecommunications, computers, multimedia, automotive systems, medical instrumentation, and robotics. When the overall requirements are stringent, attempts to implement the required analog signal processor using conventional circuits can result in very large power consumption and chip size, making the entire system impractical. This can be traced to fundamental limitations of linear circuits. To bypass such limitations, this research deals with input-output linear signal processors which are permitted to be internally nonlinear. This allows the internal signals to have, for a large input signal range, a magnitude well above that of noise and interference, while at the same time remaining safely below overload levels. The result is adequate signal integrity over the entire range, without requiring large power consumption and chip size. This approach extends the use of companding (compressing/expanding) techniques, commonly employed in signal transmission and recording, to signal processing.The first phase of this research was a study of the signal and noise properties of externally linear, internally nonlinear signal processors, as well as of signal-noise interactions. Based on the results of this phase, a study of appropriate architectures and appropriate choice of internal nonlinearities is being undertaken, with low power dissipation and practicality of implementation in mind. For these architectures and nonlinearities, appropriate circuit design techniques are being developed. Both syllabic and instantaneous companding are being considered, along with combinations thereof. The final phase of the project will be a demonstration of the results obtained using test chips, meant to satisfy a relevant set of stringent specifications. Since the processors are internally nonlinear, special attention will be given to extensive measurements for their characterization, particularly of input-output linearity, noise, signal-noise interaction, and dynamic range.