Fully integrated bandpass filters for wireless transceivers-problems and promises

Abstract

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 IO years ago, due to the demanding system-requirements of modem 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.

A Low-Cost and Low-Power CMOS Receiver Front-End for MB-OFDM Ultra-Wideband Systems

“…A varactor diode provides continuous tuning of the frequency range of the filter, although in practice digital control of a MIM capacitor array would function equally well. Various filter tuning techniques, such as those described in [16] and [17] can be used for frequency tuning of this filter.…”

A 2.5-GHz low-power, high dynamic range, self-tuned Q-enhanced LC filter in SOI

“…Since there may be strong out-of-band signals presented to the filter, bigger signal swing is a more important concern. M1 uses a special zero-threshold device offered by the target IC process, both to minimize the noise figure and to optimize the dynamic range performance in the filter [9], [10]. With the resulting 0.5-V overdrive at 0.5-V bias voltage, signals of up to 1-V peak differential can be tolerated at the filter input, translating to approximately 9-dBm input compression at the antenna terminals.…”