School of Mechanical Engineering Seminar
Monday, April 11, 2016 at 15:00
Wolfson Building of Mechanical Engineering, Room 206

Using Nonlinearity to Reduce Phase Noise in MEMS-based Oscillators

Dr. Ori Shoshani

Due to their inherent compatibility with semiconductor technology and their ability to fulfill device miniaturization requirements, micro-electro-mechanical-system (MEMS) resonating elements are an attractive replacement for quartz crystals in time-keeping applications. They offer fast-responding, low power consumption elements that are readily integrable with electronic circuits in fabrication.  However, as the dimensions of MEMS devices are reduced, resonator frequency becomes highly dependent upon fabrication variances and environmental disturbances that result in degradation of frequency stability.  Moreover, in order to satisfy signal-to-noise ratio specifications, these MEMS devices often need to operate at amplitudes where nonlinear effects come into play, which leads to further degradation in the frequency precision. This talk will provide an overview of frequency stability in MEMS-based oscillators and describe some recently developed approaches to enhancing frequency stability by addressing, and even exploiting, system nonlinearities. Specifically, the use of synchronization and zero-dispersion points in the resonator frequency response will be discussed, and theoretical conditions for optimal operating points will be introduced.  Experimental validation of the results, obtained from experimental collaborators in the Kenny group at Stanford University and in the López group at Argonne National Laboratory, will also be presented.

Bio: Oriel Shoshani received the B.S. degree in mechanical engineering from Ben-Gurion University of the Negev, Beer-Sheva, Israel, in 2008 and the Ph.D. degree (direct program) in mechanical engineering from Technion-Israel Institute of Technology, Haifa, Israel, in 2014, for which he worked on problems related to fluid-structure interactions. Currently, he is a postdoctoral fellow in the Department of Mechanical and Aerospace Engineering at Florida institute of Technology and a visiting scholar in the Department of Physics and Astronomy at Michigan State University. His current research interests include dynamics of fluctuating nonlinear vibrational systems and applications to micro/nano-electro-mechanical systems.

You are invited to attend a lecture

By

Oren Pe'eri

M.Sc student of Prof. Menachem Nathan and Prof. Michael Golub

Electrical Engineering, Physical Electronics Department

Tel Aviv University

Direct Reconstruction of Spectral Signatures in Optical-Digital Snapshot Spectral Imaging Systems

Abstract

This thesis is dedicated to a new approach in spectral imaging. We use an imaging system that includes a spectral disperser, a micro-lens array (MLA), imaging lenses and a monochromatic sensor that records a mix of spectral and spatial data ("spectral cube") in a multiplexed form. We develop a special demultiplexing algorithm for direct extraction of spatial maps corresponding to spectral signatures of interest from the sensor data. This "signature mapping" is based on prior knowledge of spectral signatures of specific materials and on the assumption that the original spectral cube consists of their linear superimposition. Direct extraction of the spatial map of signatures marks the areas where the original image is abundant in specific chemical materials. As such, it substantially reduces the data volume by a ratio of the number of wavelength bands to the number of spectral signatures. The developed method and algorithms are validated by computer simulation of the spectral imaging system with the aid of spectral cubes of real multi-spectral images of gas plumes.

Thursday, March 10, 2016, at 15:30

Room 011, Kitot building