Prof. Bernhard Boser of UC Berkeley

Abstract:

GPS has transformed navigation but unfortunately does notwork in indoor or dense urban environments. The alternative,inertial navigation, is either too inaccurate or too large, power hungry, and costly in all but niche applications.

Gyroscopes are responsible for direction in inertial sensors.Since even small angular offsets can rapidly add up to largelocation errors, significantly improved gyroscope accuracy is the key to precise indoor navigation.

I will describe a prototype gyroscope with tactical gradeperformance. Unlike state-of-the-art solutions, the device does not rely on exotic fabrication technology or trimming, and both its size and power dissipation are comparable to existing mobile solutions.

How is this possible? Sensors, in general, compare their input toa reference. A thermometer compares its input to a referencetemperature and reports the ratio. Gyroscope sensors have ahuge advantage: their input is rate, degrees per second, also known as frequency. Frequency is the physical quantity that wecan synthesize and measure with highest accuracy. While ppm-level precision is out-of-the-question for most properties, it is easily achieved for frequency.

Why then are gyroscopes not just as accurate as frequencysources? Oddly, present MEMS gyroscopes first convertfrequency into force, then displacement, capacitance, voltage.Not only are these quantities difficult to measure with highaccuracy, the scaling factors of all these transformations are subject to a myriad of fabrication and environmental variations. Not surprising that present gyroscopes suffer from a few errors.

The path to good gyroscopes is to measure frequency directly,without performance compromising detours. In this presentation, I will show you how.

Biography:

Dr. Boser received a diploma in Electrical Engineering from theSwiss Federal Institute of Technology (ETH), Zurich,Switzerland, and his M.S. and Ph.D. in EE from Stanford University, 1985 and 1988, respectively. Prior to joining thefaculty of EECS at UCBerkeley in 1991, he was a member of thetechnical staff of AT&T Bell Laboratories in Holmdel, NJ. Dr. Boser has been the Editor of the IEEE Journal of Solid-State Circuits and President of the IEEE Solid-State Circuits Society.He is a co-founder of SiTime, a company commercializing MEMSresonators to replace quartz crystals as precision timing references. His research focuses on sensors and sensor interface electronics.