Theory and design of active LC filters on silicon.

摘要

The demand for higher levels of integration in wireless transceivers calls for integrated RF filters. These filters usually have high- Q bandpass frequency response, and thus cannot be realized only with the lossy reactive components available in today's silicon technologies. Q-enhancement techniques are used in this thesis to boost the Q of reactive components. The implementation of Q enhancement involves negative resistors, which are built with transistors, and can be noisy and nonlinear. Hence, the filters' dynamic range is limited. Nevertheless, it can be shown that with the same power dissipation, the dynamic range of an active LC filter can be larger than that of a Gm-C filter. While at present the dynamic range of active LC filters may still not be large enough to meet receivers' requirement, it may be sufficient for certain applications in transmitters (for example, to clean up the signal following a mixing operation). The range of application will expand as reactive elements with higher quality factor are realized.;One problem faced by active LC filters on silicon is to achieve exact frequency response. Both on-chip inductors and capacitors have losses and parasitics to the substrate, which cannot be easily absorbed into the filter's transfer function. Pre-distortion techniques can be used to reduce this problem, but a systematic solution is still lacking.;In order to make an active LC filter insensitive to parasitics, process variations and temperature changes, an automatic tuning system is designed to be an integral part of the filter. This tuning system can tune the capacitances, and thus the center frequency of the filter, and the negative resistances, and thus the Q of the filter. In order for the tuning system to operate at high frequencies, a new tuning technique is proposed for loss control.;Two prototype filters and their tuning systems are implemented on silicon to demonstrate the feasibility for active LC filters to achieve usable dynamic range with reasonable power consumption, and to validate the proposed tuning techniques.