Calibration for wireless location system
First Claim
1. An external calibration method for a TDOA wireless location system (WLS), comprising the steps of:
- transmitting a reference signal from a reference transmitter at a known location, receiving the reference signal at first and second receiver systems, determining an error value, and using the error value to correct subsequent TDOA measurements.
2 Assignments
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Accused Products
Abstract
Methods and apparatus for calibrating a Wireless Location System to enable the system to make highly accurate TDOA and FDOA measurements are disclosed. An external calibration method in accordance with the present invention comprises the steps of transmitting a first reference signal from a reference transmitter; receiving the first reference signal at first and second receiver systems; determining a first error value by comparing a measured TDOA (or FDOA) value with a theoretical TDOA (or FDOA) value associated with the known locations of the receiver systems and the known location of the reference transmitter; and utilizing the first error value to correct subsequent TDOA measurements associated with a mobile transmitter to be located. An internal calibration method in accordance with the present invention comprises the steps of injecting a comb signal into the first receiver system; utilizing the comb signal to obtain an estimate of the manner in which the transfer function varies across the bandwidth of the first receiver system; and utilizing the estimate to mitigate the effects of the variation of the first transfer function on the time measurements made by the first receiver system.
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Citations
38 Claims
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1. An external calibration method for a TDOA wireless location system (WLS), comprising the steps of:
- transmitting a reference signal from a reference transmitter at a known location, receiving the reference signal at first and second receiver systems, determining an error value, and using the error value to correct subsequent TDOA measurements.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An external calibration method for use with a wireless location system having first and second receiver systems, wherein the location system estimates velocity using frequency difference of arrival (FDOA), comprising:
- transmitting a first reference signal from a reference transmitter at a known location, receiving the reference at the first and second receivers, determining an error value, and utilizing the error value to correct subsequent FDOA measurements.
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14. An external calibration method for use with a wireless location system including a receiver system characterized by a time- and frequency-varying transfer function, comprising the steps of:
- transmitting a stable, known wideband calibration signal from an external transmitter;
using the wideband calibration signal to estimate the transfer function across a prescribed bandwidth; and
using the estimate to mitigate effects of variation of the transfer function on subsequent time measurements. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
- transmitting a stable, known wideband calibration signal from an external transmitter;
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24. An external calibration method for calibrating a location system having a first receiver system and a second receiver system, wherein the location system is operative to estimate the location of a mobile transmitter by, in part, determining a difference in time of arrival of a signal transmitted by said mobile transmitter and received by said first and second receiver systems, and wherein the accuracy of the location estimate is dependent, in part, upon the accuracy of time difference of arrival (TDOA) measurements made by the location system, the method comprising the steps of:
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(A) transmitting a first reference signal from a reference transmitter;
(B) receiving said first reference signal at said first and second receiver systems;
(C) determining a first error value by comparing a measured TDOA value with a theoretical TDOA value associated with the known locations of the receiver systems and the known location of the reference transmitter; and
(D) utilizing said first error value to correct subsequent TDOA measurements associated with a mobile transmitter to be located. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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38. An external calibration method for calibrating a location system having a first receiver system and a second receiver system, wherein the location system is operative to estimate the location and velocity of a mobile transmitter by, in part, determining a difference in frequency of arrival of a signal transmitted by said mobile transmitter and received by said first and second receiver systems, and wherein the accuracy of the location and velocity estimate is dependent, in part, upon the accuracy of frequency difference of arrival (FDOA) measurements made by the location system, the method comprising the steps of:
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(A) transmitting a first reference signal from a reference transmitter;
(B) receiving said first reference signal at said first and second receiver systems;
(C) determining a first error value by comparing a measured FDOA value with a theoretical FDOA value associated with the known locations of the receiver systems and the known location of the reference transmitter; and
(D) utilizing said first error value to correct subsequent FDOA measurements associated with a mobile transmitter to be located.
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Specification