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System, method, and sensors for sensing physical properties

  • US 6,278,379 B1
  • Filed: 12/06/1999
  • Issued: 08/21/2001
  • Est. Priority Date: 04/02/1998
  • Status: Expired due to Term
First Claim
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1. A sensor for wirelessly determining physical properties of a medium, comprising:

  • a resonant circuit having a capacitor and an inductor;

    a substrate;

    a structural layer placed over the substrate, the structural layer defining a cavity with a diaphragm having an external surface and an internal surface, the diaphragm being moveable in response to a pressure applied to the external surface;

    the capacitor having at least a first plate positioned on the diaphragm and a second plate positioned opposite the first plate with the cavity therebetween, wherein a capacitance of the capacitor is variable with a movement of the diaphragm; and

    the inductor having a first end coupled to the first plate and a second end coupled to the second plate, the inductor inducing a current in the resonant circuit when exposed to a time-varying electromagnetic field.

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