Tag tracking
First Claim
1. A position determining system comprising:
- a tag which is operable to transmit a signal comprising first and second frequency components having a frequency spacing therebetween;
a plurality of receivers having known relative positions, each being operable to receive the signal transmitted from the tag;
a processor operable to process the signal received at each receiver to determine, for each received signal, a phase measurement for the first frequency component and a phase measurement for the second frequency component;
a calculator operable to calculate a phase difference measurement for each received signal by subtracting the phase measurement for the first frequency component from the phase measurement of the second frequency component; and
a position determiner operable to determine the relative position between the tag and the receivers on the basis of the calculated phase difference measurements for the received signals and the known relative positions of the receivers;
wherein said tag is a transmit only tag that operates asynchronously with respect to said receivers.
4 Assignments
0 Petitions
Accused Products
Abstract
The present invention provides a tracking system in which a mobile tag having an unknown position, which tag is to be tracked in space over time, transmits a signal comprising a pair of tones at different frequencies. The transmitted signal is received at each of three receivers, each having a known location, where the phase of each of the tones within the signal is measured. The measured phases are passed to a processing unit which determines the position of the tag at the time of transmission of the signal on the basis of the difference between the measured phases of the two tones. The tracking system operates over a defined finite range to track the position of the mobile tag uniquely in space.
122 Citations
43 Claims
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1. A position determining system comprising:
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a tag which is operable to transmit a signal comprising first and second frequency components having a frequency spacing therebetween; a plurality of receivers having known relative positions, each being operable to receive the signal transmitted from the tag; a processor operable to process the signal received at each receiver to determine, for each received signal, a phase measurement for the first frequency component and a phase measurement for the second frequency component; a calculator operable to calculate a phase difference measurement for each received signal by subtracting the phase measurement for the first frequency component from the phase measurement of the second frequency component; and a position determiner operable to determine the relative position between the tag and the receivers on the basis of the calculated phase difference measurements for the received signals and the known relative positions of the receivers; wherein said tag is a transmit only tag that operates asynchronously with respect to said receivers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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41. A position processor for determining the position of a transmit-only tag relative to a plurality of receivers, the receivers having known relative positions and being operable to receive a signal comprising first and second frequency components having a frequency spacing therebetween transmitted from the tag which operates asynchronously with respect to the receivers, the position processor comprising:
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a processor operable to receive a plurality of sets of phase measurements, each set associated with a respective one of the receivers and each set comprising a phase measurement for the first frequency component and a phase measurement for the second frequency component of the signal received at the corresponding receiver; a calculator operable to calculate a respective phase difference measurement for each set of phase measurements; and a position determiner operable to determine the relative position of the tag on the basis of the calculated phase difference measurements and the known relative positions of the receivers. - View Dependent Claims (42)
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43. A position determining method for determining the relative position between a transmit only tag and a plurality of receivers whose relative positions are known, the method comprising the steps of:
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operating the tag asynchronously with respect to the receivers; transmitting from the tag a signal comprising first and second frequency components having a frequency spacing therebetween; receiving at each receiver the signal transmitted by the transmitter; processing the signal received at each receiver to determine, for each received signal, a phase measurement for the first frequency component and a phase measurement for the second frequency component; calculating a phase difference measurement for each received signal by subtracting the phase measurement for the first frequency component from the phase measurement of the second frequency component; and determining the relative position between the tag and the receivers on the basis of the calculated phase difference measurements for the received signals and the known relative positions of the receivers.
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Specification