Method and apparatus for geolocating a wireless communications device
First Claim
1. A method for determining a time difference of arrival of a single signal transmitted from a transmitting unit and received at two or more receiving sites, the method comprising:
- (a) transforming the signal received at a first site to a frequency domain representation comprising first component signals each first component signal having a frequency and a phase angle parameter and transforming the signal received at a second site to a frequency domain representation comprising second component signals each second component signal having a frequency and a phase angle parameter;
(b) operating in the frequency domain, determining a Hermitian product of first and second component signals having a same frequency parameter, wherein a frequency parameter of the Hermitian product comprises the same frequency parameter;
(c) operating in the frequency domain, determining a phase angle parameter of each Hermitian product determined at the step (b);
(d) determining a relationship between the phase angles parameter and the frequency parameter for a plurality of Hermitian products; and
(e) determining the time difference of arrival from the relationship.
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Accused Products
Abstract
The time difference of arrival for a signal received at two or more receiving sites as transmitted from a wireless communications device, is determined by a frequency domain technique. The constituent frequencies of the signals received at the two or more receiving sites are determined, including the phase, or a value representative of the phase, of each frequency component. The phase values for the same frequency are subtracted to yield a phase difference values as a function of frequency. The slope of the function represents the time difference of arrival for the wireless communications device signal as received at the two receiving sites. To determine the mobile location based on the determined time difference of arrival values, a seed or initial location is first assumed for the wireless communications device and the distance difference of arrival (the time difference of arrival multiplied by the speed of light) is calculated. The calculated time difference of arrival is then used to adjust the distance difference of arrival by continuously iterating the position of the wireless communications device until the calculated distance of arrival and the calculated time difference of arrival (as multiplied by the speed of light) are within a predetermined margin.
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Citations
39 Claims
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1. A method for determining a time difference of arrival of a single signal transmitted from a transmitting unit and received at two or more receiving sites, the method comprising:
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(a) transforming the signal received at a first site to a frequency domain representation comprising first component signals each first component signal having a frequency and a phase angle parameter and transforming the signal received at a second site to a frequency domain representation comprising second component signals each second component signal having a frequency and a phase angle parameter; (b) operating in the frequency domain, determining a Hermitian product of first and second component signals having a same frequency parameter, wherein a frequency parameter of the Hermitian product comprises the same frequency parameter; (c) operating in the frequency domain, determining a phase angle parameter of each Hermitian product determined at the step (b); (d) determining a relationship between the phase angles parameter and the frequency parameter for a plurality of Hermitian products; and (e) determining the time difference of arrival from the relationship. - 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)
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25. A method for determining a time difference of arrival of a single signal transmitted from a transmitting unit and received at two or more receiving sites, the method comprising:
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(a) transforming the signal received at a first site to a first frequency domain representation comprising first component signals each first component signal having a frequency and a phase angle parameter and transforming the signal received at a second site to a frequency domain representation comprising second component signals each second component signal having a frequency and phase angle parameter; (b) operating in the frequency domain, determining a Hermitian product of first and second component signals having a same frequency parameter, wherein a frequency parameter of the Hermitian product comprises the same frequency parameter; (c) operating in the frequency domain, determining a phase function representing the phase angle of each Hermitian product as a function of the same frequency parameter; and (d) determining the time difference of arrival from the phase function. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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38. An apparatus for determining a location of a transmitting unit transmitting a signal received at two or more receiving sites, the apparatus comprising:
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an antenna at each of the two or more receiving sites responsive to the signal; a processor responsive to the antenna for transforming the signal received at a first site to a frequency domain representation comprising first component signals each first component signal having a frequency and a phase angle parameter and transforming the signal received at the second site to a frequency domain representation comprising second component signals each second component signal having a frequency and a phase angle parameter; the processor for determining a phase angle parameter of a Hermitian product of first and second component signals having a same frequency parameter, wherein a frequency parameter of the Hermitian product comprises the same frequency parameter; the processor for determining a relationship between the phase angle parameter and the frequency parameter for a plurality of Hermitian products; the processor for determining the time difference of arrival of the signal as received at the first site and the signal as received at the second site; and the processor for determining the location of the transmitting unit in response to the time difference of arrival.
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39. A computer program product for determining a time difference of arrival of a signal received at two or more receiving sites, comprising:
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a computer usable medium having computer readable program code modules embodied in the medium for determining the time difference of arrival; a computer readable first program code module operating in the frequency domain for transforming the signal received at the first site to a frequency domain representation comprising first component signals each first component signal having a frequency and a phase angle parameter and transforming the signal received at the second site to a frequency domain representation comprising second component signals each second component signal having a frequency and a phase angle parameter; a computer readable second program code module operating in the frequency domain for determining a Hermitian product of first and second component signals having a same frequency parameter, wherein a frequency parameter of the Hermitian product comprises the same frequency component; a computer readable third program code module operating in the frequency domain, for determining a phase angle parameter of each Hermitian product; a computer readable fourth program code module for determining a relationship between the phase angle parameter and the frequency parameter for a plurality of Hermitian products; and a computer readable fifth program code module for determining the time difference of arrival from the relationship.
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Specification