Fully integrated bandpass filters for wireless transceivers-problems and promises

Despite decades of research into developing true, single-chip radio transceivers, most commercial designs continue to rely on off-chip components for bandpass filtering. Implementing these filters on-chip remains nearly as challenging today as it was 10 years ago, due to the demanding system requirements of modern radio standards, and few technologies have made it into commercial production. Exceptions include the sporadic adoption of low-Q active filters in IF subsystems and the occasional use of low-Q LC filtering in front-end designs. This paper overviews filter performance requirements and implementation alternatives, and identifies fundamental as well as technological constraints limiting their use. An example design of a Q-enhanced LC filter for Bluetooth applications at 2.4 GHz is also discussed.