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.

MEMS based sensors, particularly capacitive sensors, potentially can address critical considerations for users including accuracy, repeatability, long-term stability, ease of calibration, resistance to chemical and physical contaminants, size, packaging, and cost effectiveness. Accordingly, it would be beneficial to exploit MEMS processes that allow for manufacturability and integration of resonator elements into cavities within the MEMS sensor that are at low pressure allowing high quality factor resonators and absolute pressure sensors to be implemented. Embodiments of the invention provide capacitive sensors and MEMS elements that can be implemented directly above silicon CMOS electronics.

A piezoelectrically transduced resonator device includes a wafer having a substrate, a buried oxide layer formed on the substrate, and a device layer formed on the buried oxide layer, and a resonator suspended within an air gap of the wafer above the substrate, the resonator including a portion of the device layer, a piezoelectric layer, and top and bottom electrodes contacting top and bottom sides of the piezoelectric layer, wherein the portion of the device layer is not directly connected to the wafer and wherein the resonator is configured to move relative to the substrate under electrostatic force to tune the frequency of the resonator device when a direct current voltage is applied between the substrate and the portion of the device layer of the resonator.

A MEMS device may include: (i) a lower cavity, including a first island, formed within a first layer of the MEMS device; (ii) an upper cavity, including a second island, formed within a second layer of the MEMS device; (iii) a MEMS resonating element arranged in a device layer of the MEMS device and anchored via the first and second islands; (iv) a first set of electrodes for electrostatic actuation and sensing of the MEMS resonating element in an in-plane mode that is arranged in the device layer of the MEMS device; and (v) a second set of electrodes for electrostatic actuation and sensing of the MEMS resonating element in an out-of-plane mode that is electrically isolated from the first set of electrodes and located in the first or second layer of the MEMS device, and wherein the out-of-plane mode is a torsional mode or a saddle mode.

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.sub.b, 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.

Micromachined microelectromechanical systems (MEMS) based resonators offer integration with other MEMS devices and electronics. Whilst piezoelectric film bulk acoustic resonators (FBAR) generally exhibit high electromechanical transduction efficiencies and low signal transmission losses they also suffer from low quality factors and limited resonance frequencies. In contrast electrostatic FBARs can yield high quality factors and resonance frequencies but suffer from increased fabrication complexity. lower electromechanical transduction efficiency and significant signal transmission loss. Accordingly, it would be beneficial to overcome these limitations by reducing fabrication complexity via a single metal electrode layer topping the resonator structure and supporting relatively low complexity/low resolution commercial MEMS fabrication processes by removing the fabrication requirement for narrow transduction gaps. Beneficially, embodiments of the invention provide MEMS circuits with electrostatic tuning and provide resonator designs combining the advantages of piezoelectric actuation and bulk-mode resonators.

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.

A resonator includes a first sub-resonator and a plurality of second sub-resonators. The first sub-resonator in vibration deforms in at least two non-parallel directions. The first sub-resonator is connected to the second sub-resonators in all the at least two non-parallel directions, and deformations in all the at least two non-parallel directions couple the first sub-resonator to the second sub-resonators. Then, the resonator can balance a Q value and Rm, and can have a higher Q value and lower Rm.

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 <490 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.

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 <490 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.