Johns Hopkins University

Thomas J Kistenmacher

Robert Osiander

Dennis K Wickenden

Robert B Givens

John C Murphy

Scott A Ecelberger

Daniel G Jablonski

James H Higbie

Scott T Radcliffe

Margaret Ann Darrin

Douglas A Oursler

John L Champion

A Lorentz force-driven mechanical resonator apparatus that utilizes a high-Q resonant structure as both a mixing device and a high-Q bandpass filter. Specifically, an external time varying, but quasistatic, magnetic field is applied to the resonating device while simultaneously running a time varying electrical current through the device. The resulting Lorentz force (I&times;B) is proportional to the vector product of the electrical current in the bar (I) and the external magnetic field (B). Integrating such a resonant device with a magnetic field coil produces the functionality of an ideal radio frequency (RF) mixer coupled with a high-Q intermediate frequency (IF) filter. Wide tunability provides the capability to scan, or even step, an array of filters having very narrow bandwidths via a common local oscillator to a desired frequency range.

Lorentz force driven mechanical filter/mixer designs for RF applications

A microelectromechanical-based magnetostrictive magnetometer that uses, as an active element, a commercial (001) silicon microcantilever coated with an amorphous thin film of the giant magnetostrictive alloy Terfenol-D and a compact optical beam deflection transduction scheme. A set of Helmholtz coils is used to create an ac magnetic excitation field for driving the mechanical resonance of the coated microcantilever. When the coated microcantilever is placed in a dc magnetic field, the dc field will change the amplitude at the mechanical resonance of the coated microcantilever thereby causing a deflection that can be measured. The magnetometer has been demonstrated with a sensitivity near 1 .mu.T.

Microelectromechanical (MEMS)-based magnetostrictive magnetometer

The invention consists, in one embodiment, of a resonator such as a conductive bar supported by two wires placed at the nodal points of the fundamental resonance frequency. The wires also supply current of this frequency to the resonator. In the presence of a magnetic field, the Lorentz force causes the resonator to vibrate. The amplitude of this vibration is proportional to a vector component of the magnetic field. The motion of the resonator is detected using one of a number of possible methods including optical beam deflection. The invention has a sensitivity of at least 1 nT, comparable to that of a commercial fluxgate magnetometer, and a dynamic range exceeding 80 dB.

Lorentz force magnetometer having a resonator

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Baltimore, MD, United States of America

Thomas J Kistenmacher