Electronic compass
First Claim
1. An electronic compass comprising:
- at least two coil assemblies having magnetic axes which are oriented at a known angle to each other, each said coil assembly having at least a pair of substantially identical coils having magnetic axes that are parallel in a reverse sense, each of said coils having an inductance which varies as a function of the strength of a magnetic field in which it is positioned;
at least one oscillator having frequencies of oscillation which are at least partially dependent upon the inductances of said coils;
a coil bias current source which causes current to flow in said coils;
at least one switch which alternatingly couples said coil bias current source to each of said coils of said coil assemblies; and
,a processor electrically coupled to said at least one switch which analyzes said frequencies of oscillation of said at least one oscillator when each of said coils of said coil assemblies is coupled to said coil bias current source and computes geographic orientation based upon said analysis.
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Accused Products
Abstract
An electronic compass includes at least two coil assemblies. Each coil assembly has a magnetic axis which is oriented at a known angle to that of the other coil. Each coil assembly has a pair of substantially identical coils having magnetic axes that are parallel in a reverse sense. The compass further includes an oscillator which oscillates at a frequency which is dependent upon the inductances of the coils. A current source causes current to flow in the coils and a switch alternately couples the current source to each of the coils of the coil assemblies. A processor analyzes the frequencies of oscillation of the oscillator when each of the coil assemblies is coupled to the current source in order to compute geographic orientation based upon the analysis.
411 Citations
41 Claims
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1. An electronic compass comprising:
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at least two coil assemblies having magnetic axes which are oriented at a known angle to each other, each said coil assembly having at least a pair of substantially identical coils having magnetic axes that are parallel in a reverse sense, each of said coils having an inductance which varies as a function of the strength of a magnetic field in which it is positioned; at least one oscillator having frequencies of oscillation which are at least partially dependent upon the inductances of said coils; a coil bias current source which causes current to flow in said coils; at least one switch which alternatingly couples said coil bias current source to each of said coils of said coil assemblies; and
,a processor electrically coupled to said at least one switch which analyzes said frequencies of oscillation of said at least one oscillator when each of said coils of said coil assemblies is coupled to said coil bias current source and computes geographic orientation based upon said analysis. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. An electronic compass, comprising:
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at least two coil assemblies wound around magnetically permeable cores, said coil assemblies having magnetic axes which are oriented at a known angle to each other, said coil assemblies having inductances, and said coil assemblies each comprising bifilar wound coils; at least one oscillator having frequencies of oscillation which are at least partially dependent upon the inductances of said coil assemblies; a constant current source which causes current to flow in said coils of said coil assemblies; at least one switch which alternatingly couples said constant current source to each of said coils of said coil assemblies so as to allow current from said constant current source to alternatingly flow through each of said bifilar wound coils of said coil assemblies; and
,a processor electrically coupled to said at least one switch which controls said switch and which compares said frequency of oscillation of said at least one oscillator when each of said coils of said coil assemblies is coupled to said constant current source and computes geographic orientation based upon said comparison. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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35. A method for electronically determining geographic orientation comprising the steps of:
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providing at least two coil assemblies each having a magnetically permeable core, each said coil assembly having two substantially identical bifilar wound coils having magnetic axes that are collinear but oppositely oriented, and each of said two substantially identical bifilar wound coils having an inductance which varies as a function of the strength of an externally applied magnetic field; providing an oscillator having a frequency of oscillation which is at least partially determined by said inductance of said coils; alternatingly inducing a current in each of said coils while monitoring the frequency of oscillation of said oscillator; and calculating heading from the frequency of oscillation of said oscillator when said current is induced in each of said coils. - View Dependent Claims (36, 37, 38, 39, 40)
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41. An electronic compass, comprising:
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at least two coils axially oriented at a known angle to each other, said at least two coils having inductances; at least one oscillator having frequencies of oscillation which are at least partially dependent upon said inductances of said at least two coils; a constant current source which causes current to flow in said coils of said coil assemblies; at least one switch which alternatingly couples said constant current source to each of said at least two coils as to allow current from said constant current source to alternatingly flow through each of said at least two coils; and
,a processor which analyzes said frequencies of oscillation of said at least one oscillator when each of said coils is coupled to said constant current source and computes geographic orientation based upon said analysis.
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Specification