A microfabricated tuning fork rate sensitive structure and drive electronics in which vibrational forces are communicated through a set of meshing drive and driven finger electrodes associated with each of two vibrating elements The vibrating elements are supported in a rotatable assembly between first and second support electrodes which are in turn suspended by flexures for rotation about an axis passing through the flexures and through a point midway between the vibrating elements Additional masses are formed onto the vibrating elements to improve overall sensor sensitivity Sense electrodes for detecting capacitive changes between the support electrodes and the sense electrodes are positioned at each end of the support electrodes Drive electronics are connected between the driven fingers of the vibrating elements and the drive electrode fingers which mesh with them to cause vibration Excitation is provided between the support electrodes and the sense electrodes Any change in signal resulting from rotation of the assembly and the resulting variation in capacitance between the support electrodes and the sense electrodes is sensed as a measure of inertial rate A torque loop may be additionally formed using the sense electrodes in order to re-torque the assembly to a neutral position in a torque-to-balance loop

Comb drive micromechanical tuning fork gyro

A symmetrical micromechanical gyroscope includes an inertial mass symmetrically supported about both drive and sense axes, for detecting rotational movement about an input axis Two pairs of flexures attached to diametrically opposed sides of the inertial mass support the mass within a gyroscope support frame Each of the flexures are oriented at generally a 45° angle from both the drive and the sense axes In response to an applied drive signal, the inertial mass is induced to vibrate about a drive axis which is co-planar with and orthogonal to the sense axis Both pair of flexures participate equally during rotation of the mass

Symmetrical micromechanical gyroscope

A bridge electrode structure and method of fabrication thereof is provided that is adapted to provide electrically isolated metal bridges over the active portions of a monolithic micromechanical transducer. The bridge electrode of the invention is also adapted to operate in facing relationship with one or more buried electrodes, providing top-to-bottom symmetry for balanced application of forces, or motion detection when used in conjunction with transducer elements. The transducer, typically a gyroscope or an accelerometer, includes a semiconductor substrate and active elements etched out of the substrate, the active elements including flexure-supported transducer plates. The bridge electrodes are anchored at opposing points on the substrate's surface to metal layers used to facilitate their electro-forming. The central portions of the bridge are electroplated over an insulating spacer, such as a photoresist layer.

Bridge electrodes for microelectromechanical devices

A semiconductor chip gyroscopic transducer (10) is disclosed in which a semiconductor element (47) is supported in an outer element by a flexible linkage system which is in turn supported in a frame of semiconductor material (16) by another flexible linkage system which permits the element to vibrate about two axes relative to the frame. Balanced torque forces are provided by a system of buried (50, 52, 54, 56) and bridge (58, 60, 62, 64) electrodes. The stress and tension resulting from doping of these elements are released by a flexure beam (20, 22, 36, 38). The inertial mass of the inner element is balanced by formation in a central pit and on-chip electronics avoids the capacitive loading effects of long runs from high impedance sources. Flexure footings are integrated with the structure adding stability to flexures connecting the supported gyroscopic resonator element to the supporting structure, offsetting a rippling effect inherent in the oxide structure. Flexure grooves provide selective stiffness in the flexure. The bridge electrodes (58, 60, 62, 64) are additionally electrically isolated for electrical compatibility with gyroscope electronics.

Semiconductor chip gyroscopic transducer

A micromechanical accelerometer is disclosed comprising a mass of monocrystalline silicon in which a substantially symmetrical plate attached to a silicon frame by flexible linkages is produced by selective etching. The plate has a plurality of apertures patterned and etched therethrough to speed further etching and freeing of the plate and flexible linkages, suspending them above a void etched beneath. The plate has a weight disposed thereon near an end remote from the flexible linkages. The plate is capable of limited motion about an axis created by the flexible linkages. Stop means limit motion of the plate about the axis. Strain relief tension beams are provided to relieve stress induced by boron diffusion necessary to provide etch stopping and the tension beams are trimmable in a manner which permits tuning of the resonant frequency of the plate. Grooves or depressions are provided in the flexible linkages to resist bending or buckling without increasing torsional stiffness. The plate and flexible linkages are electrically isolated from the silicon mass and frame by dielectric or P-N junction isolation. Integral P-N junction electrodes and surface bridging electrodes may be used to provide top to bottom symmetry in torquing and sensing of the plate while maintaining isolation and monlithic construction. Bias and readout circuitry used to sense and torque the plate may be provided integrally with the plate and formed during plate processing.

Monolithic micromechanical accelerometer

Microwave dielectric resonator apparatus which, for example, may be a microwave oscillator frequency stabilized by a dielectric resonator or may be a microwave filter whose critical frequency is determined by a dielectric resonator, has the dielectric resonator environmentally protected in a hermetic chamber. As the hermetic integrity of the chamber would be destroyed by having a tuning slug therein at the end of a screw threaded into a tapped hole through a chamber wall for rotation by a screwdriver outside the chamber, the tuning slug is instead located within a non-hermetic chamber at the end of a screw threaded into a tapped hole through a wall of the non-hermetic chamber serving also as an outer wall of a housing enclosing both chambers. The chambers have an interface which is transparent to microwave fields and proximate the dielectric resonator and tuning slug. The interface preserves the hermetic integrity of the hermetic chamber and transmits part of the microwave field developed by the dielectric resonator, when it resonates, to the non-hermetic chamber to be variously interfered with by the tuning slug as the slug is moved by rotation of the screw into different positional relationships of interference with the transmitted field part. As known per se, such interference alters the distribution and amount of microwave energy stored in the resonating dielectric resonator, and thereby alters the microwave frequency at which the dielectric resonator resonates. By using a puck of barium titanate as the dielectric resonator, a resonant frequency of 12 gigahertz is typically obtainable with a range of stable adjustment thereabout in the vicinity of 20 megahertz.

Allan Reynolds

Papers

Hermetically sealed oscillator with dielectric resonator tuned through dielectric window by adjusting screw