University of California

Clark T-c Nguyen

Roger T Howe

Tristan Orion Rocheleau

Liwei Lin

Thura Lin Naing

Albert P Pisano

Alper Ozgurluk

Ruonan Liu

Yang Lin

Wei-Chang Li

Jalal Naghsh Nilchi

Robert A Schneider

Albert P Pigano

Lingqi Wu

Yafei Li

System and methods for a hollow-disk radial-contour mode resonator structure. The hollow disk reduces the dynamic mass and stiffness of the structure. Since electromechanical coupling C/Cgoes as the reciprocal of mass and stiffness, the hollow disk structure has a considerably stronger electromechanical coupling than a solid one at the same frequency, and thus raises C/Cwithout excessive gap-scaling. Several embodiments of hollow disk resonators are detailed, including asymmetric and symmetric disk configurations.

High electromechanical coupling strength hollow disk resonators

An on-chip strain measurement device that uses precision frequency measurements to precisely extract sub-nm displacements, allowing residual strain measurements in a given structural film. Strain-induced gap changes to resonance frequencies use differential strategies to remove bias uncertainty, allowing measurement of sub-nm displacements. Gap-dependent electrical stiffness is used to shift resonance frequencies as structural elements stretch or shrink to relieve strain. An output based on differential frequencies between two proximal structures with unequal stress arm lengths removes uncertainty on the initial gap spacing. The ability to precisely measure the frequency of the high-Q structures allows lifetime stress correction of micromechanical circuits, such as oscillators and filters.

Electrical stiffness-based sensor

A microelectromechanical resonant switch ('resoswitch') converts received radio frequency (RF) energy into a clock output. The resoswitch first accepts incoming amplitude- or frequency-shift keyed clock-modulated RF energy at a carrier frequency, filters it, provides power gain via resonant impact switching, and finally envelop detects impact impulses to demodulate and recover the carrier clock waveform. The resulting output derives from the clock signal that originally modulated the RF carrier, resulting in a local clock that shares its originator's accuracy. A bare push-pull 1-kHz RF-powered mechanical clock generator driving an on-chip inverter gate capacitance of 5 fF can potentially operate with only 5 pW of battery power, 200,000 times lower than a typical real-time clock. Using an off-chip inverter with 17.5 pF of effective capacitance, a 1-kHz push-pull resonator would consume 17.5 nW.

RF-powered micromechanical clock generator

Active feedback is used with two electrodes of a four-electrode capacitive-gap transduced wine-glass disk resonator to enable boosting of an intrinsic resonator Q and to allow independent control of insertion loss across the two other electrodes. Two such Q-boosted resonators configured as parallel micromechanical filters may achieve a tiny 0.001% bandwidth passband centered around 61 MHz with only 2.7 dB of insertion loss, boosting the intrinsic resonator Q from 57,000, to an active Q of 670,000. The split capacitive coupling electrode design removes amplifier feedback from the signal path, allowing independent control of input-output coupling, Q, and frequency. Controllable resonator Q allows creation of narrow channel-select filters with insertion losses lower than otherwise achievable, and allows maximizing the dynamic range of a communication front-end without the need for a variable gain low noise amplifier.

Active resonator system with tunable quality factor, frequency, and impedance

A microelectromechanical resonant switch ('resoswitch') converts received radio frequency (RF) energy into an output signal with zero quiescent power usage by using a resonant element with a passband input sensitivity of: &#x3c;&#x2212;60 dBm, &#x3c;&#x2212;68 dBm, and &#x3c;&#x2212;100 dBm. The resoswitch first accepts incoming amplitude- or frequency-shift keyed RF energy at a carrier frequency, filters it, provides power gain via resonant impact switching, and finally envelop detects impact impulses to demodulate and recover the modulating waveform. Mechanical gain may be used to amplify received signals, whose amplitudes may be binned, thereby preserving use of amplitude modulated (AM) signals. A second resoswitch may be used to control additional circuitry, whereby the first resoswitch detects a control signal output to the additional circuitry.

Zero-quiescent power receiver

A micro-electromechanical system (MEMS) frequency divider apparatus having one or more MEMS resonators on a substrate is presented. A first oscillator frequency, as an approximate multiple of the parametric oscillation frequency, is capacitively coupled from a very closely-spaced electrode (e.g., 40 nm) to a resonant structure of the first oscillator, thus inducing mechanical oscillation. This mechanical oscillation can be coupled through additional MEMS resonators on the substrate. The mechanical resonance is then converted, in at least one of the MEMS resonators, by capacitive coupling back to an electrical signal which is a division of the first oscillation frequency. Output may be generated as a single ended output, or in response to a differential signal between two output electrodes.

Micromechanical frequency divider

A tunable Q resonator using a capacitive-piezoelectric transducer provides a flexible top electrode above an AlN resonator. The top electrode can be pulled electrostatically towards the resonator and substrate, forming a frictional contact with either the resonator or the combined resonator-electrode structure to the substrate, allowing for electrical tuning the Q of the resonator. With a sufficient electrostatic bias voltage V, the resonator may be completely turned OFF, allowing for an integrated switchable AlN resonator. Such switchable resonator may be integrated into a radio frequency (RF) front end as a digitally selectable band pass filter element, obviating the need for ancillary micromechanical switches in the signal path. The device has been demonstrated with a Q approaching 9,000, together with ON/OFF switchability and electromechanical coupling up to 0.63%. Flexible positioning of the top electrode allows for actively controlling the series resonant frequency of the resonator through changes in capacitive coupling.

Tunable Q resonator

A micromechanical resonator having one or more anchoring stems which are hollow to increase resonator Q factor. By way of example a micromechanical disk resonator embodiment is shown utilizing a resonant micromechanical disk anchored by a stem between at least one electrode used for input and output. To increase resonator Q, a hollow stem is utilized in which an outer thickness of stem material surrounds a hollow area interior of the stem, or that is fabricated with a plurality of vias and/or fabricated substructures containing hollow spaces in the stem material. Measurements have confirmed that Q values can be increased using the hollow core stems by a factor of 2.9 times in certain implementations and operating modes.

Hollow supports and anchors for mechanical resonators

A radio frequency (RF) MEMS resonator is embedded in an active positive feedback loop to form a tunable RF channel-selecting radio transceiver employing a super-regenerative reception scheme. This transceiver harnesses the exceptionally high Q (around 100,000) and voltage-controlled frequency tuning of a resonator structure to enable selection of any one of among twenty 1 kHz wide RF channels over an 80 kHz range, while rejecting adjacent channels and consuming &#x3c;490 &#x3bc;W. Such transceivers are well suited to wireless sensor node applications, where low-power and simplicity trump transmission rate. Electrical stiffness-based frequency tuning also allows this same device to operate as a frequency shift keyed (FSK) transmitter, making a complete transceiver in one simple device. Finally, the geometric flexibility of resonator structure design should permit a large range of usable RF frequencies, from the presently demonstrated 60.6-MHz VHF, all the way up to UHF.

MEMS-based regenerative transceiver

A circuit of N micromechanical resonant switches (resoswitches) is presented, which mimics a Dickson charge pump to amplify an input voltage to an output voltage of N plus 1 times the input voltage, while avoiding the diode voltage drop and breakdown voltage limitations of CMOS-based conventional charge pumps. Important aspects of successful charge pumping are: 1) the long cycle lifetime of resonant micromechanical switches, which has been shown to operate 173.9&#xd7;10cycles, is orders of magnitude higher than non-resonant switches; 2) the use of gated-sinusoid drive excitation to allow a charging period independent of resoswitch resonance frequency; and 3) the use of resonance operation to lower required drive and DC-bias voltages to below the supply voltage. This mechanical charge pump obviates the need for custom high voltage CMOS for applications where large voltages are needed such as MEMS-based timing references, thereby allowing the use of virtually any CMOS process.

Micromechanical resonant switches and charge pumps

A micromechanical filter having planar components, and manufacturable using very large scale integrated circuit microfabrication techniques. The input and output transducers are interdigitated comb electrodes. The mechanical coupling between the input and output transducers includes planar flexures, displacement of the electrodes producing bending of the elements of the flexures. By sealing micromechanical filters in a vacuum and providing on-board circuitry, high signal-to-noise ratios and quality factors are achievable. Construction of a real-time spectrum analyzer using many micromechanical resonators, provides a device with high accuracy and a short sample time.

Microelectromechanical signal processor fabrication

Microelectromechanical signal processors

Resonator systems with controlled quality factors including a resonator having a plurality of ports and a first quality factor greater than the system quality factor, and an amplifier providing negative feedback among the ports to render the system quality factor independent of the resonator quality factor.

Growing community of inventors

Oakland, CA, United States of America

Clark T-c Nguyen