title: Passive ultrasonics using sub-Nyquist sampling of high-frequency thermal-mechanical noise.
abstract: Monolithic integration of capacitive micromachined ultrasonic transducer arrays with low noise complementary metal oxide semiconductor electronics minimizes interconnect parasitics thus allowing the measurement of thermal-mechanical (TM) noise. This enables passive ultrasonics based on cross-correlations of diffuse TM noise to extract coherent ultrasonic waves propagating between receivers. However, synchronous recording of high-frequency TM noise puts stringent requirements on the analog to digital converter's sampling rate. To alleviate this restriction, high-frequency TM noise cross-correlations (12-25 MHz) were estimated instead using compressed measurements of TM noise which could be digitized at a sampling frequency lower than the Nyquist frequency.
authors.affiliation: School of Mechanical Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, Georgia 30332-0405 karim.sabra@me.gatech.edu.
authors.forename: Karim G
authors.initials: KG
authors.lastname: Sabra
authors.affiliation: School of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Drive NW, Atlanta, Georgia 30332-0250 jrom@ece.gatech.edu.
authors.forename: Justin
authors.initials: J
authors.lastname: Romberg
authors.affiliation: School of Mechanical Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, Georgia 30332-0405 lani.shane@gatech.edu, levent.degerteking@me.gatech.edu.
authors.forename: Shane
authors.initials: S
authors.lastname: Lani
authors.affiliation: School of Mechanical Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, Georgia 30332-0405 lani.shane@gatech.edu, levent.degerteking@me.gatech.edu.
authors.forename: F Levent
authors.initials: FL
authors.lastname: Degertekin