Dissertation Talk: Crystal-free wireless communication with relaxation oscillators and its applications

Seminar | March 8 | 2-3 p.m. | 490H Cory Hall

 David Burnett

 Electrical Engineering and Computer Sciences (EECS)

This talk pertains to extreme miniaturization of wireless systems by eliminating all off-chip components and all on-chip inductors leading to a chip-scale wireless system, the size of which is a strong function of transistor process. Current complete wireless systems, usually referred to as "modules," have been stuck at approximately 1cm x 1cm in both industry and academia because they require off-chip components in addition to the wireless IC, all assembled on a PCB. If these off-chip components were eliminated, system footprint would be dictated by the RF IC which can scale with process. The standout exception is inductors, which can occupy the majority of an RFIC's area and do not scale with process. Hence, RF communication with relaxation (ring and RC) oscillators, which do not require inductors, is the focus of this work.

We show FSK communication systems based on free-running RF ring oscillators are capable of good packet delivery rate (PDR 99% or better) with moderately higher tone spacing compared to commercial low-power wireless specifications (~2x when communicating with COTS base station, ~6x when communicating to another ring-based radio). In addition to examining performance and demonstrating communication, we demonstrate relaxation oscillator-based radios used in an example chemical sensor system application and explore other applications potentially benefitting from such reduced form factors.