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Aspects of this invention include a downhole assembly having a non-contact, capacitive coupling including first and second transceivers deployed in corresponding first and second downhole tool members. The capacitive coupling is disposed to transfer electrical signals between the first and second tr

Aspects of this invention include a downhole assembly having a non-contact, capacitive coupling including first and second transceivers deployed in corresponding first and second downhole tool members. The capacitive coupling is disposed to transfer electrical signals between the first and second transceivers. In one exemplary embodiment, the capacitive coupling is configured to transfer data and power between a substantially non-rotating tool member and a rotating tool member, for example, the shaft and blade housing in a steering tool. Exemplary embodiments of this invention provide a non-contact, high-speed data communication channel between first and second members of a downhole assembly. Moreover, exemplary embodiments of the invention also provide for simultaneous non-contact transmission of electrical power between the first and second tool members.

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1. A downhole assembly comprising: a shaft deployed to rotate in a tool housing,a non-contact, capacitive coupling device including first and second capacitively coupled transceivers and a dielectric gap therebetween, the first transceiver deployed in the shaft and the second transceiver deployed in

1. A downhole assembly comprising: a shaft deployed to rotate in a tool housing,a non-contact, capacitive coupling device including first and second capacitively coupled transceivers and a dielectric gap therebetween, the first transceiver deployed in the shaft and the second transceiver deployed in the tool housing, the capacitive coupling device disposed to transfer an electrical signal between the shaft and the tool housing. 2. The downhole assembly of claim 1, comprising a member of the group consisting of mud motors and steering tools. 3. The downhole assembly of claim 1, wherein the electrical signal comprises at least one member selected from the group consisting of electrical power and data. 4. The downhole assembly of claim 1, wherein the first and second transceivers comprise first and second co-axial, electrically conductive cylinders. 5. The downhole assembly of claim 1, wherein the first and second transceivers are deployed in corresponding first and second electrically insulative transceiver housings, the first transceiver housing being deployed in the shaft and the second transceiver housing being deployed in the tool housing. 6. The downhole assembly of claim 5, further comprising at least one spring member deployed between the second transceiver housing and the tool housing. 7. The downhole assembly of claim 5, further comprising at least one bearing member deployed between the first and second transceiver housings and disposed to maintain a substantially constant gap thickness between the transceivers. 8. The downhole assembly of claim 7, wherein the bearing member comprises a journal bearing. 9. The downhole assembly of claim 5, further comprising an anti-rotation tab disposed to prevent relative rotation between the second transceiver housing and the tool housing. 10. The downhole assembly of claim 5, wherein the first and second transceivers are disposed to translate together in a cross axial direction. 11. The downhole assembly of claim 5, wherein the first and second transceivers are disposed to translate together in an axial direction. 12. The downhole assembly of claim 5, wherein the dielectric gap between the first and second transceivers is at least partially filled with lubricating oil. 13. The downhole assembly of claim 5, further comprising first and second electronic transceiver circuits, the first transceiver circuit electrically connected to the first transceiver and the second transceiver circuit electrically connected to the second transceiver, the first and second transceiver circuits disposed to transfer the electrical signal between the transceivers. 14. The downhole assembly of claim 13, wherein each of the first and second transceiver circuits comprises a data transceiver circuit, each of the data transceiver circuits disposed to transmit and receive data between the transceivers. 15. The downhole assembly of claim 13, wherein: the first transceiver circuit comprises a power transmitter circuit disposed to transmit electrical power from the first transceiver; andthe second transceiver circuit comprises a power receiver circuit disposed to receive electrical power at the second transceiver. 16. A downhole drilling assembly comprising: a shaft disposed to rotate in a tool housing;a magnetic ring deployed about the shaft, the magnetic ring including a plurality of circumferentially alternating magnets;an armature deployed in the housing and substantially coaxially about the magnetic ring, the armature including a plurality of radial windings such that rotation of the shaft in the housing produces AC electrical power; anda non-contact, capacitive coupling device including first and second capacitively coupled transceivers and a dielectric gap therebetween, the first transceiver deployed in the shaft and the second transceiver deployed in the tool housing, the capacitive coupling device disposed to transfer an electrical signal between the shaft and the tool housing. 17. The downhole drilling assembly of claim 16, wherein the first transceiver comprises the magnetic ring and the second transceiver comprises the armature. 18. The downhole drilling assembly of claim 16, comprising a member of the group consisting of mud motors and steering tools. 19. The downhole drilling assembly of claim 16, wherein the electrical signal comprises a data signal. 20. The downhole drilling assembly of claim 16, wherein the magnetic ring is electrically insulated from the shaft and the armature is electrically insulated from the tool housing. 21. The downhole drilling assembly of claim 16, wherein the dielectric gap between the magnetic ring and the armature is at least partially filled with lubricating oil. 22. The downhole drilling assembly of claim 16, further comprising first and second electronic transceiver circuits, the first transceiver circuit electrically connected to the first transceiver and the second transceiver circuit electrically connected to the second transceiver, the first and second transceiver circuits disposed to transfer the electrical signal between the transceivers. 23. The downhole drilling assembly of claim 22, wherein each of the first and second transceiver circuits comprises a data transceiver circuit, each of the data transceiver circuits disposed to transmit and receive data between the transceivers.