Patent ID: 8581579

Claim:
A sensor apparatus for sensing magnetic signals with a sensed signal frequency range, comprising: a sensor stack comprising alternating layers of at least two layers of magneto-strictive material and at least one layer of piezo-electric material, configured with the at least one piezo-electric layer between, and physically attached to, the at least two magneto-strictive layers; and a biasing arrangement configured to apply to the magneto-strictive layers a time-varying biasing magnetic field, the biasing magnetic field including a substantially constant (DC) bias component and a time-varying bias component with a carrier signal frequency; such that magneto-strictive layers exhibit a magneto-strictive response to a heterodyned magnetic signal corresponding to heterodyning the time-varying biasing magnetic field and the sensed magnetic signal; and wherein the piezo-electric layer is responsive to the magneto-strictive response to the heterodyned magnetic signal to generate electrical signals corresponding to the heterodyned magnetic signal at the heterodyned frequency.