Biography
Enrollment Date: 2004
Graduation Date：2006
Degree：M.S.
Defense Date：2006.12.26
Advisors：Yongming Li
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Design and Study of Intermediate Frequency Analog Integrated Circuit
Abstract:
Receiver is a key part of the realization of wireless communication system, since its performance directly affects communication quality. In the wireless receiver, because the magnitude of input signal is neither predictable nor stable, adjusting its dynamic range is very important for signal processing. Thus, a high performance automatic gain control system (AGC) circuit plays an important role in the receiver. In this dissertation, the pivotal technicals of immediate frequency (IF) analog integrated circuits design are researched and applied for digital audio broadcasting (DAB) receiver. The main content is focused on how to analysis and design AGC circuit. Studying and implementing this kind of circuits not only have a value to conclude analog circuit design essentials, but also have some realistic meanings such as to be used as a part of all kinds of SOC chips, in which signal magnitude needs to be controlled. As is widely known, the IF analog integrated circuits are always required for high linearity and wide band, sometimes high driven capability is also needed. This dissertation particularly analysises the crucial problems in such analog circuits design, and draws some interesting but useful conclusions. Except that, the negative feedback circuits are widely discussed in the dissertation, especially the AGC loop as an amplitude negative feedback. Many relevant publications are inspected as references. The main part of this dissertation is design and implementation of DAB IF analog circuits, including Peak-detector, IF mixer, LO driver, voltage and current reference and of course variable gain amplifier (VGA), which is the most important circuit block. This dissertation novelly applies a traditional linearization method to an exponential control VGA, which both improves its linearity and enlarges its control range. What’s more, a DC-offset cancellation circuit is intruduced to improve VGA’s mismatch tolerance. All of the two schemes are at a very little price of power consumption. The whole IF circuit system for DAB receiver is implemented in UMC 0.18um CMOS process. The measurement results of the chip are also discussed. Conclusion and outlook of the project are in the last chapter.