Oscillator having micro-electromechanical resonators and driver circuits therein that support in-phase and out-of-phase signals

• US 8,242,663 B2
• Filed: 02/14/2011
• Issued: 08/14/2012
• Est. Priority Date: 09/10/2008
• Status: Expired due to Fees

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Ayazi, Farrokh, Abdolvand, Reza, Lavasani, Seyed Hossein Miri
• Primary Examiner(s): Budd, Mark
• Application Number:
  US13/027,074
• Publication Number:
  US 20110133848A1
• Time in Patent Office: 547 Days
• Field of Search: 310/321, 310/317, 310/319, 310/316.01
• US Class Current: 310/317
• CPC Class Codes: H03B 2200/0046 including measures to switch the gain of an amplifier
• CPC Class Codes: H03B 2200/0048 including measures to switch the frequency band, e.g. by harmonic selection
• CPC Class Codes: H03B 5/326 the resonator being an acoustic wave device, e.g. SAW or BAW device
• CPC Class Codes: H03B 5/366 and comprising means for varying the frequency by a variable voltage or current
• CPC Class Codes: H03H 2009/02173 of film bulk acoustic resonators [FBAR]
• CPC Class Codes: H03H 2009/0233 comprising perforations
• CPC Class Codes: H03H 2009/02496 Horizontal, i.e. parallel to the substrate plane
• CPC Class Codes: H03H 2009/241 Bulk-mode MEMS resonators
• CPC Class Codes: H03H 9/02228 Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer
• CPC Class Codes: H03H 9/02259 Driving or detection means
• CPC Class Codes: H03H 9/172 Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume
• CPC Class Codes: H03H 9/2463 Clamped-clamped beam resonators

Abstract

A micro-electromechanical resonator self-compensates for process-induced dimensional variations by using a resonator body having a plurality of perforations therein. These perforations may be spaced along a longitudinal axis of the resonator body, which extends orthogonal to a nodal line of the resonator body. These perforations, which may be square or similarly-shaped polygonal slots, may extend partially or entirely though the resonator body and may be defined by the same processes that are used to define the outer dimensions (e.g., length, width) of the resonator body.

Claims

1. An oscillator comprising:

a micro-electromechanical resonator having first and second electrodes, said micro-electromechanical resonator configured to resonate at a first frequency when the first and second electrodes are carrying in-phase signals and resonate at a second frequency when the first and second electrodes are carrying out-of-phase signals, said micro-electromechanical resonator comprising a thin-film piezoelectric material that supports resonant operation of the micro-electromechanical resonator; and

a driver circuit configured to selectively sustain either the in-phase signals or the out-of-phase signals on the first and second electrodes so that the resonator selectively resonates at either the first frequency or the second frequency, respectively, said driver circuit comprising first and second inverting amplifiers, which are serially connected between the first and second electrodes to thereby sustain the in-phase signals, and a switch configured to bypass one of the first and second inverting amplifiers to thereby sustain the out-of-phase signals at 180°

relative to each other.

2. The oscillator of claim 1, wherein the micro-electromechanical resonator comprises a Thin-film Piezoelectric-on-Substrate (TPoS) resonator.

3. The oscillator of claim 2, wherein the TPoS resonator comprises:

a substrate;

a single crystal silicon plate suspended from the substrate; and

a thin-film piezoelectric layer extending between the first and second electrodes and the single-crystal silicon plate.