Electromagnetically coupled hermetic chamber

Abstract

An electromagnetically coupled hermetic chamber includes a body defining a hermetic chamber. A distributed LC circuit is disposed within the hermetic chamber and a second conductive structure is attached to the body outside of the hermetic chamber. The distributed LC circuit is electromagnetically coupled to the second conductive structure without direct electrical paths thereby allowing coupling of the distributed LC circuit to external electronics without the need for electrical feedthroughs or vias that could compromise the integrity of the hermetic chamber.

1 . An apparatus comprising:
 a monolithic body of substantial uniformity defining a hermetic chamber having an upper wall and an opposed lower wall;   a distributed LC circuit disposed within the hermetic chamber, wherein a first portion of the distributed LC circuit is fixed to the upper wall of the chamber, and wherein a second portion of the distributed LC circuit is fixed to an upper surface of the lower wall of the chamber and is positioned oppositely disposed and substantially parallel to the first portion of the distributed LC circuit; and   a second conductive structure fixedly disposed on a bottom surface of the lower wall outside the hermetic chamber in spaced, substantially parallel opposition to the second portion of the distributed LC circuit,   wherein the distributed LC circuit is electromagnetically coupled to the second conductive structure without direct electrical paths connecting the distributed LC circuit and the second conductive structure.   
     
     
         2 . The apparatus of  claim 1 , further comprising means physically attached to the lower wall of the hermetic chamber for at least partially enclosing and isolating the second conductive structure; 
     
     
         3 . The apparatus of  claim 1 , wherein the electrical characteristics of the distributed LC circuit are altered by variations in the geometry of the hermetic chamber. 
     
     
         4 . The apparatus of  claim 3 , further comprising means responsive to a change in an environmental parameter for varying the geometry of the hermetic chamber. 
     
     
         5 . The apparatus of  claim 1 , wherein the monolithic sensor body is formed by thermal bonding. 
     
     
         6 . The apparatus of  claim 2 , wherein the means physically attached to at least one of the walls defining the hermetic chamber for at least partially enclosing the second conductive structure comprises a coating physically contacting at least a portion of the at least one of the walls defining the hermetic chamber and at least partially encapsulating the second conductive structure. 
     
     
         7 . The apparatus of  claim 2 , wherein the means for at least partially enclosing the second conductive structure comprises a cavity defined by the sensor body separate from the hermetic chamber, and wherein the second conductive structure is disposed within the cavity. 
     
     
         8 . The apparatus of  claim 2 , wherein the means physically attached to at least one of the walls defining the hermetic chamber for at least partially enclosing the second conductive structure comprises means physically attached to at least one of the walls defining the hermetic chamber for completely enclosing the second conductive structure. 
     
     
         9 . The apparatus of  claim 1 , wherein the first portion of the distributed LC circuit comprises a first planar spiral coil, wherein the second portion of the distributed LC circuit comprises a second planar spiral coil, wherein the first and second planar spiral coils are disposed in parallel, spaced-apart relation. 
     
     
         10 . The apparatus of  claim 9 , wherein the second conductive structure comprises a third planar spiral coil, and wherein the second and third spiral coils are disposed in parallel, spaced-apart relation. 
     
     
         11 . A sensor for indicating a physical state within a patient, comprising:
 a monolithic sensor body of substantial uniformity formed by thermal bonding defining a hermetic chamber having an upper wall and a lower wall;   a distributed LC circuit disposed within the hermetic chamber and having an element providing an inductance, wherein a first portion of the distributed LC circuit is fixed to the upper wall of the chamber, and wherein a second portion of the distributed LC circuit is positioned oppositely disposed and substantially parallel to the first portion of the distributed LC circuit and is fixed to an upper surface of the lower wall of the chamber;   a second conductive structure fixedly disposed on a bottom surface of the lower wall outside the hermetic chamber in spaced, substantially parallel opposition to the second portion of the distributed LC circuit; and   means for connecting the second conductive structure to remote electronics disposed outside of the sensor body, wherein the second conductive structure can be excited using time-varying electrical excitation via the remote electronics and, subsequently, electromagnetically coupled to the distributed LC circuit disposed within the hermetic chamber, and wherein there are no direct electrical paths connecting the distributed LC circuit disposed within the hermetic chamber to the second conductive structure disposed outside the hermetic chamber.   
     
     
         12 . The sensor of  claim 11 , further comprising means physically attached to the lower wall of the hermetic chamber for at least partially enclosing and isolating the second conductive structure. 
     
     
         13 . The sensor of  claim 11 , wherein each of the distributed LC circuit and the second conductive structure comprise a capacitor. 
     
     
         14 . The sensor of  claim 11 , wherein the distributed LC circuit and the second conductive structure comprise inductors. 
     
     
         15 . The sensor of  claim 11 , wherein the body comprises ceramic material. 
     
     
         16 . The sensor of  claim 15 , wherein the ceramic material is selected from the group consisting of glass, fused silica, sapphire, quartz, and silicon. 
     
     
         17 . The sensor of  claim 16 , wherein the body comprises fused silica. 
     
     
         18 . The sensor of  claim 11 , wherein a portion of the sensor body defining the hermetic chamber comprises a deflective region deflectable in response to a physiologically relevant pressure; and wherein at least a portion of the first portion of the distributed LC circuit is coupled to the deflective region. 
     
     
         19 . The sensor of  claim 11 , wherein the distributed LC circuit disposed within the hermetic chamber provides a capacitance and an inductance. 
     
     
         20 . The sensor of  claim 11 , wherein the distributed LC circuit further comprises: a first element providing an inductance; and a second element providing a capacitance, the first and second elements being electrically connected. 
     
     
         21 . The sensor of  claim 12 , wherein the means for isolating at least a major portion of the second conductive structure from the ambient comprises a coating. 
     
     
         22 . The sensor of  claim 21 , wherein the coating is selected from the group consisting of polyimide, liquid crystal polymer (LCP), urethane, polyester, Teflon, FEP, PTFE, polyamide and silicone rubber. 
     
     
         23 . The sensor of  claim 21 , wherein the coating comprises silicone rubber. 
     
     
         24 . The sensor of  claim 12 , wherein the means for connecting the second conductive structure to remote electronics disposed outside of the hermetic chamber comprises wires connected to the second conductive structure and extending through the means for isolating the second conductive structure from the ambient. 
     
     
         25 . The sensor of  claim 12 , wherein the means for isolating at least a major portion of the second conductive structure from the ambient comprises ceramic material. 
     
     
         26 . The sensor of  claim 25 , wherein the ceramic material is selected from the group consisting of glass, fused silica, sapphire, quartz, and silicon. 
     
     
         27 . The sensor of  claim 26 , wherein the ceramic material is fused silica. 
     
     
         28 . The sensor of  claim 25 , wherein the means for connecting the second structure to remote electronics comprises electrical feedthroughs disposed across the isolating means and coupled to the second structure. 
     
     
         29 . The sensor of  claim 11 , wherein the second conductive structure is further connected to an integrated circuit. 
     
     
         30 . The sensor of  claim 14 , wherein the means for isolating at least a major portion of the second conductive structure from the ambient comprises a cavity defined by the sensor body separate from the hermetic chamber. 
     
     
         31 . The sensor of  claim 30 , wherein the integrated circuit is further coupled to electrical feedthroughs communicating between the second chamber and the ambient. 
     
     
         32 . The sensor of  claim 11 , wherein the means physically attached to at least one of the walls defining the hermetic chamber for at least partially enclosing the second conductive structure comprises means physically attached to at least one of the walls defining the hermetic chamber for completely enclosing the second conductive structure. 
     
     
         33 . The sensor of  claim 11 , wherein the first portion of the distributed LC circuit comprises a first planar spiral coil, wherein the second portion of the distributed LC circuit comprises a second planar spiral coil, wherein the first and second planar spiral coils are disposed in parallel, spaced-apart relation. 
     
     
         34 . The sensor of  claim 33 , wherein the second conductive structure comprises a third planar spiral coil, and wherein the second and third spiral coils are disposed in parallel, spaced-apart relation.