Locating system and method
First Claim
1. A method for determining the origin of a radio signal transmission, the radio transmission being received by at least three spaced radio signal receiving stations, each station having a radio transmission receiver and a synchronizable timer, said method comprising the steps of:
- (1) at each of the stations(a) detecting a signal transmission;
(b) demodulating the detected transmission for obtaining an amplitude varying signal;
(c) detecting the transitions of the amplitude varying signal through a predetermined reference value;
(d) synchronizing the timer to a common time base;
(e) determining the times of occurrence of each of a sequential plurality of transitions of the amplitude varying signal through the predetermined reference level; and
(f) transmitting the times of occurrences to a central processing facility;
(2) at the central processing facility(g) comparing the pattern of the sequential times of occurrences detected at one of the stations to those detected at another of the stations for identifying common signal transmissions;
(h) aligning the common signal transmissions;
(i) determining a time shift necessary for effecting the steps of aligning; and
(j) computing the origin of the transmission from the determined time shift.
3 Assignments
0 Petitions
Accused Products
Abstract
The present invention includes both a system and a method for locating a source of a randomly modulated signals. In one form of the invention at least three receiving stations receive and process the randomly modulated signal. A common reference level is selected at each of the receiving stations. The times of arrival at each receiving station of the selected transitions of the signal with reference to the common reference level are determined. Each of the receiving stations provides an indication of the selected transitions to a center facility for processing to provide an indication of the location of the signal.
88 Citations
23 Claims
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1. A method for determining the origin of a radio signal transmission, the radio transmission being received by at least three spaced radio signal receiving stations, each station having a radio transmission receiver and a synchronizable timer, said method comprising the steps of:
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(1) at each of the stations (a) detecting a signal transmission; (b) demodulating the detected transmission for obtaining an amplitude varying signal; (c) detecting the transitions of the amplitude varying signal through a predetermined reference value; (d) synchronizing the timer to a common time base; (e) determining the times of occurrence of each of a sequential plurality of transitions of the amplitude varying signal through the predetermined reference level; and (f) transmitting the times of occurrences to a central processing facility; (2) at the central processing facility (g) comparing the pattern of the sequential times of occurrences detected at one of the stations to those detected at another of the stations for identifying common signal transmissions; (h) aligning the common signal transmissions; (i) determining a time shift necessary for effecting the steps of aligning; and (j) computing the origin of the transmission from the determined time shift. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A system for determining the origin of a randomly modulated radio signal transmission, the system including at least three spaced radio receiving stations, each station having a radio signal receiver and a synchronizable timer, the system comprising;
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means at each station for receiving and demodulating said received signal transmission and for detecting zero crossing transitions of the demodulated signal; means for sampling the timer at each of the detected zero crossing transitions for obtaining a time of occurrence of each transition; means for storing a set of zero crossing transition times of occurrences; means for comparing the sets of transition times from each of the stations for identifying a common signal sequence; and means for determining the time difference between the transition times at each of the stations of the common signal sequence for establishing a difference in time of arrival of the common signal sequence at each station for enabling computation of the origin of the transmission with respect to the stations. - View Dependent Claims (13, 14, 15)
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16. A method of identifying a common signal received by two or more receivers at spaced locations comprising the steps of:
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converting the signal received at each receiver to an amplitude varying signal; identifying each transition of each amplitude varying signal through a predetermined reference amplitude level; determining the time of occurrences of each transition with respect to a reference time mark common to each receiver; forming a time sequence of the times of occurrences of the transitions at each receiver; aligning the time sequences from different ones of the receivers using the reference time mark; comparing the sequences to identify corresponding transitions based upon the pattern established by time differences between consecutive ones of the transitions; and identifying common signals based upon coincidence of the time differences between consecutive transitions. - View Dependent Claims (17)
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18. A method for detecting the location of a source of a randomly modulated emission, said method comprising the steps of;
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providing at least three receiving stations at known locations, each station receiving and converting said randomly modulated emission into an electrical signal which varies randomly in a manner corresponding to the modulation of said emission; selecting a common reference level for said randomly varying electronic signal at each of said receiving stations; detecting transitions of said randomly varying electrical signal through said common reference level; transmitting to a central processing facility indication signals for each station representative of the time of occurrence of each transition, which thus represents the time of arrival of a corresponding segment of said randomly modulated emission to the respective receiving station; identifying at said central processing facility the indication signals which represent the same transition; determining the time differences between said indication signals for the same transition; and
thereaftercomputing the location of the randomly modulated emission from said indication signal time differences. - View Dependent Claims (19, 20, 21, 22)
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23. A method for identifying at a central facility the location of a randomly modulated emission received by three receivers at spaced locations, comprising the steps of:
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at each receiver converting the received randomly modulated emission into an amplitude varying electrical signal; generating a reference time mark common to all receivers; determining the times of occurrence of each transition of the amplitude varying signal through a predetermined reference amplitude level with respect to the reference time mark; transmitting a sequence of the times of occurrence to the central processing facility; at the central processing facility receiving the time occurrence sequence from the receivers; analyzing and identifying the pattern established by time differences between consecutive transitions; and
thereaftercomputing the location of the randomly modulated emission using the time difference between the time of occurrence between common transitions.
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Specification