System and method for determining the time difference of arrival of a frequency shift keyed signal at two separate receivers
First Claim
1. A system for determining the time difference of arrival of a signal between two separate locations, comprising:
- a first receiver located at a first site for generating first signal samples representing an FSK signal in response to receiving the FSK signal at time TA ;
a second receiver located at a second site for generating second signal samples representing the FSK signal in response to receiving the FSK signal at time TB, where TA ≠
TB ;
a first computer for estimating a first set of frequency shift times of the FSK signal in response to receiving the first signal samples and a time reference signal, and for generating a first output signal representing the first set of frequency shift times; and
a second computer for estimating a second set of frequency shift times of the FSK signal using the second signal samples and time reference signal, and for determining the time difference of arrival of the FSK signal between the first and second receivers using the first output signal, and the second set of frequency shift times in accordance with the relation;
space="preserve" listing-type="equation">TDOA={[t.sub.2 (1)-t.sub.1 (1)]+[t.sub.2 (2)-t.sub.1 (2)]+[t.sub.2 (3)-t.sub.1 (3)] . . . +[t.sub.2 (K)-t.sub.1 (K)]}/(K), where {t1 (1), t1 (2), t1 (3), . . . t1 (K)} represent a K number of first frequency shift times within an N number of the first signal samples, {t2 (1), t2 (2), t2 (3), . . . t2 (K)} represent a K number of second frequency shifts times within an N number of the second signal samples, and where K and N are positive integers.
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Abstract
A system determines the time difference of arrival of a frequency shift kd signal (FSK) source at two separate receiver sites. The system includes a first receiver located at a first site for generating a first series of signal samples in response to detecting an FSK signal from a FSK signal source. A second receiver located at a second site generates a second series of signal samples in response to detecting the FSK signal. A first computer estimates first frequency shift times of the FSK signal in response to receiving the first series of signal samples and a time reference signal, and generates a first output signal representing the first frequency shift times. A second computer estimates second frequency shift times of the FSK signal using the second series of signal samples and time reference signal, and determines the path difference between the FSK signal source and each of the first and second receivers using the first output signal containing the first frequency shift times, and the second frequency shift times. The invention obviates the need for providing a replica of the first signal samples to the second computer.
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Citations
14 Claims
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1. A system for determining the time difference of arrival of a signal between two separate locations, comprising:
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a first receiver located at a first site for generating first signal samples representing an FSK signal in response to receiving the FSK signal at time TA ; a second receiver located at a second site for generating second signal samples representing the FSK signal in response to receiving the FSK signal at time TB, where TA ≠
TB ;a first computer for estimating a first set of frequency shift times of the FSK signal in response to receiving the first signal samples and a time reference signal, and for generating a first output signal representing the first set of frequency shift times; and a second computer for estimating a second set of frequency shift times of the FSK signal using the second signal samples and time reference signal, and for determining the time difference of arrival of the FSK signal between the first and second receivers using the first output signal, and the second set of frequency shift times in accordance with the relation;
space="preserve" listing-type="equation">TDOA={[t.sub.2 (1)-t.sub.1 (1)]+[t.sub.2 (2)-t.sub.1 (2)]+[t.sub.2 (3)-t.sub.1 (3)] . . . +[t.sub.2 (K)-t.sub.1 (K)]}/(K),where {t1 (1), t1 (2), t1 (3), . . . t1 (K)} represent a K number of first frequency shift times within an N number of the first signal samples, {t2 (1), t2 (2), t2 (3), . . . t2 (K)} represent a K number of second frequency shifts times within an N number of the second signal samples, and where K and N are positive integers. - View Dependent Claims (2)
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3. A method for determining the time difference of arrival of a signal between two separate locations, comprising the steps of:
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detecting an FSK signal with a first receiver at a first location; generating first signal samples representing the FSK signal; detecting the FSK signal with a second receiver at a second location; generating second signal samples representing the FSK signal; estimating a first set of frequency shift times of the FSK signal from the first signal samples and a time reference signal; generating a first output signal representing the first set of frequency shift times; estimating a second set of frequency shift times of the FSK signal from the second series of signal samples and time reference signal; and determining the time difference of arrival of the FSK signal at the first and second receivers using the first output signal, and the second set of frequency shift times, wherein the time difference of arrival is determined in accordance with the relation;
space="preserve" listing-type="equation">TDOA={[t.sub.2 (1)-t.sub.1 (1)]+[t.sub.2 (2)-t.sub.1 (2)]+[t.sub.2 (3)-t.sub.1 (3)] . . . +[t.sub.2 (K)-t.sub.1 (K)]}/K,where {t1 (1), t1 (2), t1 (3), . . . t1 (K)} represent a K number of the first frequency shift times within an N number of the first signal samples, {t2 (1), t2 (2), t2 (3), . . . t2 (K)} represent a K number of the second frequency shifts times within an N number of the second signal samples, and K and N are positive integers.
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4. A system for determining the time difference of arrival of a signal at two separate locations, comprising:
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a first receiver located at a first site for generating first signal samples representing a signal that transitions between first and second states; a second receiver located at a second site for generating second signal samples representing the signal; a first computer for estimating a first set of transition times within the signal in response to receiving the first signal samples and a time reference signal, and for generating a first output signal representing the first set of transition times, where the first transition times occur when the signal transitions between the first and second states; and a second computer for estimating a second set of transition times within the signal using the second series of signal samples and time reference signal, and for determining the time difference of arrival of the signal at the first and second receivers using the first output signal, and the second set of transition times, wherein the time difference of arrival is determined in accordance with the relation;
space="preserve" listing-type="equation">TDOA={[t.sub.2 (1)-t.sub.1 (1)]+[t.sub.2 (2)-t.sub.1 (2)]+[t.sub.2 (3)-t.sub.1 (3)] . . . +[t.sub.2 (K)-t.sub.1 (K)]}/K,where {t1 (1), t1 (2), t1 (3), . . . t1 (K)} represent a K number of first frequency shift times within an N number of the first signal samples, {t2 (1), t2 (2), t2 (3), . . . t2 (K)} represent a K number of second frequency shifts times within an N number of the second signal samples, and K and N are positive integers. - View Dependent Claims (5, 6)
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7. A method for determining the time difference of arrival of a signal at two separate locations, comprising the steps of:
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detecting a signal that transitions between first and second states with a first receiver at a first location; generating first signal samples representing the signal; detecting the signal with a second receiver at a second location; generating second signal samples representing the signal; estimating a first set of transition times of the signal from the first signal samples and a time reference signal, where the first transition times occur when said signal transitions between the first and second states; generating a first output signal representing the first transition times; estimating a second set of transition times of the signal from the second signal samples and time reference signal, where the second transition times occur when said signal transitions between the first and second states; and determining the time difference of arrival of the signal at the first and second receivers using the first output signal and the second transition times, wherein said time difference of arrival is determined in accordance with the relation;
space="preserve" listing-type="equation">TDOA={[t.sub.2 (1)-t.sub.1 (1)]+[t.sub.2 (2)-t.sub.1 (2)]+[t.sub.2 (3)-t.sub.1 (3)] . . . +[t.sub.2 (K)-t.sub.1 (K)]}/K,where {t1 (1), t1 (2), t1 (3), . . . t1 (K)} represent a K number of first frequency shift times within an N number of the first signal samples, {t2 (1), t2 (2), t2 (3), . . . t2 (K)} represent a K number of second frequency shifts times within an N number of the second signal samples, and K and N are positive integers.
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8. A system for determining the time difference of arrival of a signal between two separate locations, comprising:
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a first receiver for receiving a signal that transitions between two different states and for transforming said signal into an n number of pairs of first in-phase and quadrature signal samples, where n is a positive integer index; a first computer for determining; a) phase values P1 (n) for each of said first in-phase and quadrature signal samples; and b) transition times t1 (1), t1 (2), t1 (3), . . . t1 (k1) when said signal transitions between said first and second states, where k1 represents the number of transitions detected from said n number of first in-phase and quadrature signal samples, and said transition times are determined from said phase values P1 (n); a second receiver for transforming said signal into an n number of pairs of second in-phase and quadrature signal samples; and a second computer for determining; a) phase values P2 (n) for each of said second in-phase and quadrature signal samples; b) transition times t2 (1), t2 (2), t2 (3), . . . t2 (k2) when said signal transitions between said first and second states, where k2 represents the number of transitions detected from said n number of second in-phase and quadrature signal samples, k2 =k1, and said transition times are determined from said phase values P2 (n); and c) a time difference of arrival TDOA of said signal between said first and second receivers, where
space="preserve" listing-type="equation">TDOA={[t.sub.2 (1)-t.sub.1 (1)]+[t.sub.2 (2)-t.sub.1 (2)]+[t.sub.2 (3)-t.sub.1 (3)] . . . +[t.sub.2 (k.sub.1)-t.sub.1 (k.sub.1)]}/k.sub.1. - View Dependent Claims (9)
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10. A method for determining the time difference of arrival of a signal between two separate locations, comprising the steps of:
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receiving a signal at a first location where said signal transitions between two different states; transforming said signal into an n number of pairs of first in-phase and quadrature signal samples, where n is a positive integer index; determining phase values P1 (n) for each of said first in-phase and quadrature signal samples; determining transition times t1 (1), t1 (2), t1 (3), . . . t1 (k1) when said signal transitions between said first and second states, where k1 represents the number of transitions detected from said n number of first in-phase and quadrature signal samples, and said transition times are determined from said phase values P1 (n); receiving said signal at a second location; transforming said signal into an n number of second in-phase and quadrature signal samples; determining phase values P2 (n) for each of said second in-phase and quadrature signal samples; determining transition times t2 (1), t2 (2), t2 (3), . . . t2 (k2) when said signal transitions between said first and second states, where k2 represents the number of transitions detected from said n number of second in-phase and quadrature signal samples, k2 =k1, and said transition times are determined from said phase values P2 (n); and determining a time difference of arrival TDOA of said signal between said first and second receivers, where;
space="preserve" listing-type="equation">TDOA={[t.sub.2 (1)-t.sub.1 (1)]+[t.sub.2 (2)-t.sub.1 (2)]+[t.sub.2 (3)-t.sub.1 (3)] . . . +[t.sub.2 (k.sub.1)-t.sub.1 (k.sub.1)]}/k.sub.1. - View Dependent Claims (11)
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12. A method for determining the time difference of arrival of a signal between two separate locations, comprising the steps of:
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receiving a signal at a first location where said signal transitions between two different states; transforming said signal into an n number of pairs of first in-phase and quadrature signal samples, where n is a positive integer index; determining phase values P1 (n) for each of said first in-phase and quadrature signal samples; determining first transition times t1 (1), t1 (2), t1 (3), . . . t1 (k1) when said signal transitions between said first and second states, where k1 represents the number of transitions detected from said n number of first in-phase and quadrature signal samples, and said transition times are determined from said phase values P1 (n); receiving said signal at a second location; transforming said signal into an n number of second in-phase and quadrature signal samples; determining phase values P2 (n) for each of said second in-phase and quadrature signal samples; determining second transition times t2 (1), t2 (2), t2 (3), . . . t2 (k2) when said signal transitions between said first and second states, where k2 represents the number of transitions detected from said n number of second in-phase and quadrature signal samples, k2 =k1, and said transition times are determined from said phase values P2 (n); and determining a time difference of arrival TDOA of said signal between said first and second receivers from said first transition times transition times t1 (1), t1 (2), t1 (3), . . . t1 (k1), and second transition times t2 (1), t2 (2), t2 (3), . . . t2 (k2). - View Dependent Claims (13, 14)
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Specification