US6177792B1 — Mutual induction correction for radiator coils of…

Claim 1

Independent Claim 88 words

Apparatus for tracking an object by generating magnetic fields, comprising: a plurality of radiator coils; driver circuitry coupled thereto, which drives the coils so as to generate magnetic fields at a plurality of driving frequencies, wherein each of the plurality of radiator coils generates a field substantially only at a single, respective driving frequency; and circuitry associated with at least one of said plurality of radiator coils for substantially eliminating magnetic fields generated by the at least one coil in response to fields generated by the other coils.

Claim 2

Dependent Claim 88 words

Apparatus for tracking an object by generating magnetic fields, comprising: a plurality of radiator coils; driver circuitry coupled thereto, which drives the coils so as to generate magnetic fields at a plurality of driving frequencies, wherein each of the plurality of radiator coils generates a field substantially only at a single, respective driving frequency; and circuitry associated with at least one of said plurality of radiator coils for substantially eliminating magnetic fields generated by the at least one coil in response to fields generated by the other coils.

Claim 3

Dependent Claim 18 words

Apparatus in accordance with claim 1 , wherein said circuitry for eliminating comprises one or more shimming coils.

Claim 4

Dependent Claim 27 words

Apparatus in accordance with claim 2 , wherein the one or more shimming coils are interwound with the at least one of said plurality of radiator coils.

Claim 5

Dependent Claim 46 words

Apparatus in accordance with claim 3 , wherein the driver circuitry further drives one of the one or more shimming coils associated with the at least one of said plurality of radiator coils at the respective frequency of another one of said plurality of radiator coils.

Claim 6

Dependent Claim 17 words

Apparatus in accordance with claim 4 , wherein the circuitry for eliminating includes an adaptive current supply.

Claim 7

Dependent Claim 40 words

Apparatus in accordance with claim 5 , wherein the adaptive current supply generates electrical current in the at least one of said plurality of radiator coils at the respective driving frequency of another one of said plurality of radiator coils.

Claim 8

Dependent Claim 23 words

Apparatus in accordance with claim 6 , wherein the circuitry for eliminating further includes a current analyzer coupled to the adaptive current supply.

Claim 9

Dependent Claim 60 words

Apparatus in accordance with claim 7 , wherein the current analyzer measures parasitic electrical current flowing in the at least one of said plurality of radiator coils at the respective driving frequency of another one of said plurality of radiator coils, and causes the adaptive current supply to adjust the generated current so as to minimize the parasitic electrical current.

Claim 10

Dependent Claim 30 words

Apparatus in accordance with claim 1 , wherein the driver circuitry maintains a constant current in each of the plurality of radiator coils at the single, respective driving frequency thereof.

Claim 11

Independent Claim 97 words

A method for tracking an object by generating a magnetic field having a desired narrow frequency band, comprising: driving a radiator coil with electrical current at a frequency in the desired narrow frequency band; analyzing the current flowing in the coil to measure induced current components at one or more undesired frequencies; and adaptively driving the radiator coil with correction current components at the one or more undesired frequencies, wherein the correction current components are substantially equal in amplitude and opposite in phase to the induced current components measured at the respective one or more undesired frequencies.

Claim 12

Independent Claim 97 words

A method for tracking an object by generating a magnetic field having a desired narrow frequency band, comprising: driving a radiator coil with electrical current at a frequency in the desired narrow frequency band; analyzing the current flowing in the coil to measure induced current components at one or more undesired frequencies; and adaptively driving the radiator coil with correction current components at the one or more undesired frequencies, wherein the correction current components are substantially equal in amplitude and opposite in phase to the induced current components measured at the respective one or more undesired frequencies.

Claim 13

Dependent Claim 71 words

A method in accordance with claim 10 , comprising: generating a plurality of magnetic fields having a plurality of respective desired narrow frequency bands in a vicinity of an object being tracked; placing one or more sensor coils at a locatable site on the object; receiving signals generated by the sensor coils in response to the magnetic fields; and analyzing the signals to determine position and orientation coordinates of the object.

Claim 14

Independent Claim 96 words

A method for tracking an object, comprising: driving a plurality of radiator coils with electrical currents at a plurality of respective frequencies, so as to generate magnetic fields in a vicinity of an object being tracked; placing one or more sensor coils at a locatable site on the object; receiving signals generated by the sensor coils in response to the magnetic fields; analyzing the signals to determine uncorrected position and orientation coordinates of the object; and correcting the position and orientation coordinates to account for errors due to mutual inductance among the plurality of radiator coils.

Claim 15

Independent Claim 96 words

A method for tracking an object, comprising: driving a plurality of radiator coils with electrical currents at a plurality of respective frequencies, so as to generate magnetic fields in a vicinity of an object being tracked; placing one or more sensor coils at a locatable site on the object; receiving signals generated by the sensor coils in response to the magnetic fields; analyzing the signals to determine uncorrected position and orientation coordinates of the object; and correcting the position and orientation coordinates to account for errors due to mutual inductance among the plurality of radiator coils.

Claim 16

Dependent Claim 87 words

A method in accordance with claim 12 , wherein the position and orientation coordinates are corrected by the steps of: determining parasitic magnetic fields that would be generated at the uncorrected position of the object due to mutual inductance; computing parasitic signal components that would be generated by the sensor coils in response to the parasitic magnetic fields; calculating corrected signals by subtracting the parasitic signal components from the signals received from the sensor coils; and analyzing the corrected signals to determine corrected position and orientation coordinates.

Claim 17

Dependent Claim 33 words

A method in accordance with claim 13 , wherein determining the parasitic magnetic fields comprises analyzing the current flowing in the plurality of radiator coils to measure induced current components at undesired frequencies.

Claim 18

Dependent Claim 26 words

A method in accordance with claim 13 , wherein determining the parasitic magnetic fields comprises calculating theoretically the mutual inductance among the plurality of radiator coils.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2004-01-23	2004-07-24	2005-01-23	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2008-01-23	2008-07-24	2009-01-23	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2012-01-23	2012-07-24	2013-01-23	$7700.00	Window Closed / Lapsed

Mutual induction correction for radiator coils of an objects tracking system

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