News Column

Researchers Submit Patent Application, "Microphone System with Mechanically-Coupled Diaphragms", for Approval

June 5, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Liu, Fang (Woburn, MA); Yang, Kuang L. (Newton, MA), filed on November 9, 2012, was made available online on May 22, 2014.

The patent's assignee is Invensense, Inc.

News editors obtained the following quote from the background information supplied by the inventors: "Micro-electromechanical ('MEMS') components and processes are used for a wide variety of different devices. For example, among other things, they are commonly used for producing accelerometers to detect acceleration, pressure sensors to detect pressure, power scavengers to accumulate power, and as microphones to capture acoustic signals.

"MEMS capacitive microphones in particular have found a wide variety of different uses, such as in consumer electronics (e.g., cameras), smart phones and personal computers. This wide use is due in part to their higher stability and smaller size than traditional condenser microphones. As the technology improves, there is an increasing demand to enhance acoustic quality--in particular, higher sensitivity. In general, the dynamic range of a microphone is limited at the upper end by total harmonic distortion and at the lower end by its noise floor."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "In a first embodiment of the invention, a microphone system for detecting an acoustic signal includes a micromachined device having a backplate; a primary diaphragm separated from the backplate by a variable primary gap; the primary diaphragm and the backplate forming a variable primary capacitance across the primary gap, such that the primary capacitance varies in response to the acoustic signal impinging on the primary diaphragm; a reference electrode; a reference diaphragm separated from the reference electrode by a variable reference gap, the reference diaphragm forming a variable reference capacitance with the reference electrode across the variable reference gap; and a mechanical coupler coupling the primary diaphragm to the reference diaphragm. The mechanical coupler is configured to vary the reference gap inversely and proportionately to the variation of primary gap, and to vary the reference capacitance inversely and proportionately to the reference capacitance.

"In some embodiments, the mechanical coupler includes a torsion bar supported by at least one anchor coupled to a substrate, the torsion bar between the primary diaphragm and the reference diaphragm; and a beam coupled to the torsion bar, the primary diaphragm, and the reference diaphragm, the beam mechanically coupling the primary diaphragm to the reference diaphragm.

"In some embodiments, the primary capacitance is about equal to the reference capacitance when the microphone is not subject to an acoustic signal.

"In some embodiments, the primary diaphragm defines a diaphragm plane when not subject to an acoustic signal, and wherein the reference diaphragm is nominally within the diaphragm plane, and is radially spaced from the primary diaphragm.

"In some embodiments, the primary diaphragm and the reference diaphragm define an electrical node. Indeed, in some embodiments, the primary diaphragm, the mechanical coupler, and the reference diaphragm define an electrical node.

"Some embodiments also include a substrate having a frontside and a backside, and the substrate includes a backside cavity extending into the backside of the substrate, and the primary diaphragm suspended from the frontside and exposed through the backside cavity.

"In some embodiments, the system further includes a differential circuit having a non-inverting input and an inverting input, the primary capacitance electrically coupled to the non-inverting input and the reference capacitance coupled to the inverting input. Indeed, in some embodiments the differential circuit is a differential amplifier. In some embodiments, the primary diaphragm is suspended parallel to the backplate, and in some embodiments the reference diaphragm is suspended parallel to the reference electrode.

"In some embodiments, the primary capacitance has a nominal primary capacitance value, and the reference capacitance has a nominal reference capacitance value equal to the primary capacitance value. Further, in some embodiments the primary capacitance has a nominal primary capacitance value, and the reference capacitance has a nominal reference capacitance value, and the reference capacitance has a nominal reference capacitance value equal to the primary capacitance value.

"In some embodiments, the microphone has a substrate that includes the backplate and the reference diaphragm. Further, in some embodiments the substrate includes a trough opposite the reference diaphragm.

"In some embodiments, the primary diaphragm defines a diaphragm plane, and the reference diaphragm has an annular geometry and surrounds the primary diaphragm within the diaphragm plane. Indeed, in some embodiments the reference diaphragm and the primary diaphragm are concentric.

"In another embodiment, a packaged microphone system for detecting an acoustic signal includes a housing with a base; a lid coupled to the base and covering the aperture to form a cavity, one of the base and the lid forming an aperture extending from the cavity to the environment outside of the housing; and also includes a MEMS microphone secured within the cavity and being in acoustic communication with the aperture, the MEMS microphone forming a backside cavity, and being coupled to the base such that the backside cavity covers the aperture; a backplate supported by the substrate, a primary diaphragm suspended from the substrate and forming a variable primary capacitance with a backplate; a reference diaphragm suspended from the substrate and laterally spaced from the primary diaphragm, the reference diaphragm forming a variable reference capacitance with the reference electrode; a mechanical coupler coupling the primary diaphragm to the reference diaphragm, the reference diaphragm being configured to move in antiphase to the primary diaphragm when an acoustic signal impinges on the primary diaphragm.

"In some embodiments, the reference diaphragm is not directly exposed to the aperture such that there is no direct acoustic path from the base aperture to the reference diaphragm.

"In some embodiments, the primary diaphragm and the reference diaphragm are concentric.

"In another embodiment, a microphone system for detecting an acoustic signal includes a micromachined device having a backplate; a primary diaphragm suspended parallel to the backplate and separated from the backplate by a variable primary gap to form a variable primary capacitance across the primary gap, the primary capacitance varying in response to the acoustic signal impinging on the primary diaphragm; a reference electrode; a reference diaphragm suspended parallel to the reference electrode and separated from the reference electrode by a variable reference gap to form a variable reference capacitance with the reference electrode across the variable reference gap; and means for mechanically coupling the primary diaphragm to the reference diaphragm, the mechanically coupling means being configured to vary the reference gap inversely and proportionately to the primary gap in response to impingement of the acoustic signal on the primary diaphragm such that the reference capacitance varies inversely and proportionately to the primary capacitance.

"In some embodiments, the means for mechanically coupling includes means for supporting a torsion bar from a substrate, the torsion bar between the primary diaphragm and the reference diaphragm; and a beam coupled to the torsion bar, the primary diaphragm, and the reference diaphragm, wherein the beam mechanically couples the primary diaphragm to the reference diaphragm.

"In some embodiments the system further includes a circuit for producing an output signal in response to changes in the primary capacitance and the reference capacitance.

BRIEF DESCRIPTION OF THE DRAWINGS

"The foregoing features of embodiments will be more readily understood by reference to the following detailed description, taken with reference to the accompanying drawings, in which:

"FIGS. 1A and 1B schematically illustrate a MEMS microphone;

"FIGS. 2A-2K schematically illustrate embodiments of a MEMS microphone with mechanically-coupled diaphragms, and various features of such microphones;

"FIG. 3 schematically illustrates an embodiment of a MEMS microphone;

"FIG. 4A schematically illustrates inversely variable capacitances of an embodiment of a MEMS microphone;

"FIG. 4B schematically illustrates a circuit for producing an output signal from inversely variable capacitances;

"FIG. 5 is a flow chart that illustrates a method of fabricating an embodiment of a substrate for a MEMS microphone;

"FIGS. 6A-6E schematically illustrate features of an embodiment of a substrate for a MEMS microphone at various stages of fabrication;

"FIG. 7A schematically illustrates an embodiment of a packaged MEMS microphone system;

"FIG. 7B schematically illustrates an alternate embodiment of a packaged MEMS microphone system;

"FIGS. 8A-8C schematically illustrate alternate embodiments of two-diaphragm microphones;

"FIG. 9 schematically illustrates an alternate embodiment of a packaged MEMS microphone system;

"FIG. 10 schematically illustrates an alternate embodiment of a microphone with conductive electrodes."

For additional information on this patent application, see: Liu, Fang; Yang, Kuang L. Microphone System with Mechanically-Coupled Diaphragms. Filed November 9, 2012 and posted May 22, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=3619&p=73&f=G&l=50&d=PG01&S1=20140515.PD.&OS=PD/20140515&RS=PD/20140515

Keywords for this news article include: Invensense Inc.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


For more stories covering the world of technology, please see HispanicBusiness' Tech Channel



Source: Politics & Government Week


Story Tools






HispanicBusiness.com Facebook Linkedin Twitter RSS Feed Email Alerts & Newsletters