title: Regenerative feedback resonant circuit to detect transient changes in electromagnetic properties of semi-insulating materials.
abstract: A prototype regenerative feedback resonant circuit has been developed for measuring the transient spectral response due to perturbations in properties of various electromagnetic materials. The circuit can accommodate a variety of cavity resonators, shown here in the 8 GHz range, with passive quality factors (Qstat) as high as 7000 depending upon material loading. The positive feedback enhanced dynamic quality factors (Qdyn) of resonator∕material combinations in the regenerative circuit are on the order of 10(7)-10(8). The theory, design, and implementation of the circuit is discussed along with real-time monitored example measurements of effects due to photon-induced charge carriers in high-resistivity silicon wafers and magnetic-field induced perturbations of yttrium-iron garnet.
authors.affiliation: Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
authors.forename: A Mark
authors.initials: AM
authors.lastname: Jones
authors.forename: James F
authors.initials: JF
authors.lastname: Kelly
authors.forename: Ronald H
authors.initials: RH
authors.lastname: Severtsen
authors.forename: John S
authors.initials: JS
authors.lastname: McCloy