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US 2002/0172223 A1Published application
Calibration for wireless location system
OwnerLouis A. Stilpinventor
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OwnerLouis A. Stilpinventor
Estimating the term…
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.
An external calibration method for a TDOA wireless location system (WLS), comprising the steps of:
A method as recited in claim 3, wherein the first and second error values are combined in a weighted average.
An internal calibration method for a receiver system characterized by a time- and frequency-varying transfer function, wherein the receiver system is used in a wireless location system, comprising the steps of:
An external calibration method for use with a wireless location system having first and second receivers, wherein the location system estimates velocity using frequency difference of arrival (FDOA), comprising:
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:
An external synchronization system for a receiver system used in a wireless location system (WLS), comprising a GPS receiver, an oven controlled crystal oscillator, and a phase-locked loop that generates various signals required for use within the receiver system, each signal being synchronized in time and frequency to a signal output by the GPS receiver, and each generated signal having a low phase noise.
A method for calibrating and correcting for station biases in a receiver system employed in a wireless location system (WLS), the receiver system comprising an antennae array, cabling, a filter, preamplifier, and a wideband receiver, and a station bias defined as the finite delay between when an RF signal from a mobile transmitter reaches the antennae and when that same signal reaches the wideband receiver, comprising the steps of:
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:
An internal calibration method for calibrating a first receiver system, wherein said first receiver system is characterized by a time- and frequency-varying transfer function, said transfer function defining how the amplitude and phase of a received signal will be altered by said first receiver system, and wherein the first receiver system is utilized in a location system that is operative to determine the location of a mobile transmitter by, in part, determining a difference in time of arrival of a signal transmitted by a mobile transmitter and received by said first receiver system and another receiver system, and wherein the accuracy of the location determination is dependent, in part, upon the accuracy of time measurements made by said receiver systems, the method comprising the steps of:
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:
Dependencies are inferred from the claim text.