IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0806179
(2007-05-30)
|
등록번호 |
US-7436359
(2008-10-14)
|
발명자
/ 주소 |
|
출원인 / 주소 |
- Northrop Grumman Systems Corporation
|
인용정보 |
피인용 횟수 :
6 인용 특허 :
9 |
초록
▼
A method of locating a terrestrial emitter of electromagnetic radiation in the midst of a plurality of emitters in a satellite in orbit about the earth which utilizes a location estimation and location probability determination process with respect to each possible emitter site and its corresponding
A method of locating a terrestrial emitter of electromagnetic radiation in the midst of a plurality of emitters in a satellite in orbit about the earth which utilizes a location estimation and location probability determination process with respect to each possible emitter site and its corresponding error region and then using both feedback and feed forward interaction between location and phase ambiguity resolution processes to generate resolved phase from emitter location, update emitter location or some or all of the emitters, and subsequently utilizing the probabilities thus determined to produce a single estimate of the desired emitter's location.
대표청구항
▼
What is claimed is: 1. A method of determining the true location of an emitter by an array of sensors each detecting signals from the emitter and including means for processing data from the array and generating therefrom information indicative of emitter location, wherein the array of sensors comp
What is claimed is: 1. A method of determining the true location of an emitter by an array of sensors each detecting signals from the emitter and including means for processing data from the array and generating therefrom information indicative of emitter location, wherein the array of sensors comprises an incomplete array and a set of multiple possible emitter locations is initially generated, with one location of the set being, within sensor measurement error, the true location, and where the remaining locations of the set comprise ambiguous spurious locations of the emitter that cannot be distinguished from the true location of the emitter, and where the true location is subsequently determined without necessarily uniquely resolving location ambiguity; comprising the steps of: (a) measuring a set of initial incomplete array data at an initial array location; (b) initializing a location estimator for all possible emitter site locations; (c) determining and storing estimates of all said emitter site locations associated with said set of initial incomplete array data where one of said estimates is, within said sensor measurement error, the true emitter site location; (d) moving the sensor array relative to the emitter, (e) measuring another set of incomplete array data at the subsequent array location; (f) predicting from each emitter site location determined in step (c) the data measured in step (e); (g) associating uniquely the array data from step (e) with an emitter site from step (c) by utilizing the predicted data from step (f); (h) altering the measured data from step (e) utilizing the associated predicted data from step (g), so the altered data is, to within said sensor measurement error, data that would be measured by a complete array of sensors if the emitter were located at the associated, possibly spurious, site; (i) inputting the respective altered associated data from step (h) into the corresponding location estimator from step (b), updating each estimate of emitter site location initialized in step (b), and generating updated predicted measurement data; (j) replacing each stored location estimate of step (c) with the respective updated emitter site location estimate from step (i); (k) comparing the updated predicted data from step (i) with the measured data from step (e), and determining a probability for each updated emitter site location estimate that each said location estimate is the true emitter site location of said one emitter; and (l) generating an estimate of said true emitter site location based on the probability determined in step (k). 2. The method of determining the true location of an emitter in accordance with claim 1 additionally including a step (m) of repeating step (d) through step (l) until the estimate from step (l) converges, within said sensor measurement error and a processing error tolerance, to the true emitter location. 3. A method of locating a terrestrial emitter of electromagnetic radiation at a satellite in an orbit about the earth, comprising the steps of: (a) initially detecting a signal from said emitter at the satellite during a first predetermined dwell time; (b) measuring the difference in phase of the wavefront of the detected signal from said emitter arriving at pairs of antennas selectively located on the satellite, wherein the measured phase difference is sufficient to produce a set of direction of arrival (DOA) vectors with one vector of the set, within a measurement error, being the true direction of arrival of the detected signal from said emitter; (c) generating a set of all possible phase measurement ambiguity integers, one for each antenna pair, consistent with the frequency of the signal from said emitter and the orientation of the pair of antennas during step (b) and, wherein one subset of said set of ambiguity integers includes a true subset of ambiguity integers; (d) determining all possible DOA vectors by resolving the phase with each ambiguity integer associated with said subset of ambiguity integers; (e) determining and storing estimates of all possible emitter site locations associated with said set of DOA vectors and where one of said estimates is, within said measurement error, the true emitter site location; (f) initializing a location estimator for each said possible emitter site of said set of possible emitter sites; (g) detecting the signal from said emitter again during a second predetermined dwell time following said first dwell time wherein the satellite has moved in its orbit relative to said emitter, and then measuring the phase difference during said second time interval according to step (b); (h) generating a new set of phase measurement ambiguity integers during said second predetermined dwell time following the movement of the satellite in step (g); (i) predicting a new set of DOA vectors, utilizing the stored emitter estimated positions from step (e) and the satellite orbital position following the phase difference measuring step in step (g); (j) predicting a new subset of phase measurement ambiguity integers with each new DOA vector consistent with the orientation of said pair of antennas during said second dwell time; (k) resolving the measured phase difference of step (g) with each ambiguity integer of said new subset of phase measurement ambiguity integers generated in step (h); (l) inputting the respective resolved measured phase difference of step (k) into the respective location estimator initialized in step (fl, and updating each estimate of emitter site location initialized in step (f); (m) replacing each stored location estimate of step (e) with the respective updated emitter site location estimate; (n) determining a probability for each updated emitter site location estimate by determining a likelihood that each said location estimate is the true emitter site location of said one emitter; (o) generating an estimate of said true emitter site location based on the probability determined in step (o); and (p) repeating step (g) through step (o) until the estimate from step (o) converges, within said measurement error and a predetermined processing error tolerance, to the true emitter location. 4. A method of locating terrestrial emitters of electromagnetic radiation using a calibrated but ambiguous interferometer array mounted on a satellite, the satellite being in an orbit producing translational motion of the array relative to one or more of said emitters on the earth's surface, the method comprising the steps of: (a) controlling a tuning frequency of an intercept receiver on the satellite to detect diverse emitters, and upon detecting a transmitted signal from said one or more emitters associating a respective unique tuning frequency with each detected emitter; (b) measuring the phase difference of the signal wavefront of said transmitted signal intercepted by an antenna array, where the phase difference is measured modulo one phase cycle, and provides a set of ambiguous direction of arrival (DOA) vectors for the detected emitter, and wherein one vector of said set of DOA vectors within a measurement error, being the true direction of arrival DOA for the one emitter associated with the phase measurements; (c) generating a set of all possible phase measurement ambiguity integers, consistent with emitter intercept or tuning frequency and orientation of said antennas, during the phase difference measuring step of step (b), and wherein one subset of ambiguity integers of said set of ambiguity integers includes a subset of true ambiguity integers correctly resolving the modulo one cycle phase measurement ambiguities for the associated emitter; (d) determining all possible DOA vectors from the ambiguous measured phase utilizing all said ambiguity integers; (e) determining and storing estimates of all possible emitter site locations associated with said DOA vectors and where one estimate is, within a predetermined measurement error, the true emitter site location for the detected emitter associated with that set; (f) tuning the intercept receiver, utilizing said associated unique tuning frequency and at least one other signal characteristic of said one or more detected emitters to detect the transmitted signals from said one or more emitters following movement of said satellite relative to said one or more emitters; then for each; (g) measuring a new set of ambiguous phase differences and generating a new set of ambiguity integers per steps (b) and (c); (h) adjusting the stored previous estimate of said emitter site locations from step (e) so as to account for the earth's rotation during the orbital movement of said satellite in step (f); (i) generating a new set of DOA vectors utilizing the adjusted stored emitter site location estimates and satellite orbital position at the new receiver dwell time, (j) generating with each DOA vector of said new set of DOA vectors, a new set of ambiguity integers in response to the orientation of said antenna array at the new receiver dwell time; (k) updating or resolving the ambiguous measured phase differences from step (g) with said new set of ambiguity integers; (l) initializing an emitter site location estimator or location filter for each DOA vector of said new set of DOA vectors; (m) updating each estimate of possible emitter site locations established in step (l) by inputting the respective phase differences resolved in step (k); (n) replacing each stored location estimate in step (e) with said updated emitter site location estimate; (o) determining a value of the probability or likelihood that one of the updated emitter site locations is a true location; (p) generating an estimate of the true emitter site location utilizing said probability or likelihood values determined in step (o); and (q) repeating the steps (f)-(k) and steps (m)-(p) while the emitter is detected in step (f). 5. A method of locating a terrestrial emitter of electromagnetic radiation on the earth's surface using a calibrated but ambiguous antenna array interferometer mounted on a satellite, the satellite being in an orbit producing translational motion of the array relative to said emitter, comprising the steps of: (a) detecting a transmitted signal from said emitter during an initial receiver dwell time; (b) measuring the phase difference of the signal wavefront of said transmitted signal intercepted by an antenna array located on the satellite, where the phase measured is sufficient to produce a set of direction of arrival (DOA) vectors, and wherein one vector of said DOA vectors within a measurement error, being the true direction of arrival DOA; (c) generating a set of all possible phase measurement ambiguity integers, consistent with emitter frequency and orientation of said antenna array during the phase difference measuring step of step (b), and wherein one subset of ambiguity integers of said set of ambiguity integers includes a subset of true ambiguity integers; (d) determining all possible DOA vectors utilizing all said ambiguity integers; (e) determining and storing estimates of all possible emitter site locations associated with said DOA vectors and where one estimate is within a measurement error, the true emitter site location; (f) initializing an emitter site location estimator or location filter for each estimated emitter site from step (e) during said new dwell time; (g) detecting a transmitted signal from said emitter during a new receiver dwell time utilizing the frequency and other signal characteristics of said one emitter, following subsequent translational movement of said satellite relative to said emitter; (h) measuring a new set of ambiguous phase differences and generating a new set of ambiguity integers per steps (b) and (c); (i) adjusting the stored previous estimate of said emitter site locations so as to account for the earth's rotation during the orbital movement of said satellite in step (g); (j) generating a new set of DOA vectors utilizing the adjusted stored emitter site location estimates and satellite orbital position during the new receiver dwell time; (k) generating with each DOA vector of said new set of DOA vectors, a new set of ambiguity integers in response to the orientation of said at least one pair of antennas at the new receiver dwell time; (l) updating the measured phase differences with said new set of ambiguity integers; (m) updating each estimate of possible emitter site locations by inputting the respective phase differences resolved in step (k) into the respective estimator initialized in step (f); (n) replacing each stored location estimate in step (e) with the respective updated emitter site location estimate; (o) determining a value of the probability or likelihood that one of the updated emitter site locations is the true emitter site location; (p) generating an estimate of the true emitter site location utilizing said probability or likelihood values determined in step (o); and (q) tuning the intercept receiver and detecting the transmitter signal for multiple successive orbital movements of said satellite relative to said emitter, and repeating the steps (g)-(p). 6. The method of claim 5 where the step (p) of generating an estimate of the true emitter site location utilizes the probability or likelihood values as weights further comprises computing a weighted average of all of the individual probability or likelihood values. 7. The method of claim 5 where the step (p) of generating an estimate of the true emitter site location includes utilizing the probability or likelihood values and then determining the emitter site location estimate having the maximum probability value. 8. The method of claim 5 wherein the step (p) of generating an estimate of the true emitter site location further comprises: (i) utilizing the probability or likelihood values as weights and then computing a weighted average of all of the individual probability or likelihood values, and (ii) utilizing the probability or likelihood values and then determining the emitter site location estimate having the maximum probability value. 9. The method of claim 5 further comprising (r) of terminating the method when the weighted average estimate value and the maximum probability value are, within a predetermined estimation statistical error, substantially the same. 10. The method of claim 5 wherein the individual emitter site location estimates are stored in earth-centered inertial (ECI) coordinates, and thereafter rotated in ECI coordinates to adjust for the time between successive receiver phase measurements of steps (b) and (g). 11. The method of claim 5 wherein the individual emitter site location estimates are initialized in step (f) and updated in step (m) in local south-east-up or SEZ coordinates. 12. The method of claim 5 wherein said interferometer includes at least two antenna elements. 13. The method of claim 5 wherein said interferometer includes three antenna elements. 14. The method of claim 5 wherein said interferometer includes a plurality of antenna elements, and wherein said antenna elements are placed at locations with spacings at relatively prime integer multiples, where the spacings are along one, two, or three dimensions. 15. The method of claim 5 wherein each array of the interferometer array comprises two antenna elements and an interferometer baseline generated by a satellite latitude change. 16. The method of claim 5 wherein the interferometer array comprises two non-coboresited or squinted antennas, wherein said two antennas are switched to either of two orthogonal polarization modes, with an ambiguous phase measurement being made between the two antennas for both of said modes and an elevation measurement being made by comparing the two sets of phase measurements. 17. The method of claim 5 wherein the antennas of the interferometer array have a variable separation distance requiring an additional step of (s) determining the position of said antenna with respect to the satellite in the phase difference measuring steps (b) and (h). 18. The method of claim 5 wherein the intercept receiver comprises a two channel receiver. 19. The method of claim 5 wherein the intercept receiver comprises a single channel receiver including a storage device for storing phase difference measurements measured in step (b) and following measurements in step (h) being made relative to a precision internal clock. 20. The method of claim 19 wherein the storage device comprises a digital RF memory. 21. The method of claim 5 wherein the measurements of phase difference of steps (b) and (h) are generated by one antenna relative to a precision internal clock, and wherein interferometer baselines are generated by comparing phase measurements made relative to the internal clock at different satellite attitudes. 22. The method of claim 5 wherein the antenna elements forming the interferometer array comprises a subset of the total set of antenna elements required to form a fully populated and resolved interferometer, and where some integers determined in step (c) and step (k) are determined by conventional interferometer array processing. 23. The method of claim 5 wherein the step (o) of determining the value of the probability or likelihood includes determining the accuracy of the ambiguity resolution for each site location, and, if the accuracy resolution is correct, further including the step (g) of determining the accuracy of each emitter site location estimate. 24. Apparatus for locating a terrestrial emitter of electromagnetic radiation at a satellite in an orbit about the earth: (a) means for initially detecting a signal from said emitter at the satellite; (b) means for measuring the difference in phase of the wavefront of the detected signal from said emitter arriving at least one pair of antennas selectively located on the satellite, wherein the measured phase difference is sufficient to produce a set of direction of arrival (DOA) vectors, with one vector of the set, being the true direction of arrival of the detected signal from one of said emitter; (c) means for generating a set of all possible phase measurement ambiguity integers consistent with the frequency of the signal from said emitters and the orientation of the pair of antennas and wherein one subset of said set of ambiguity integers includes a true subset of ambiguity integers; (d) means for determining all possible DOA vectors by resolving the phase with each ambiguity integer associated with said subset of ambiguity integers; (e) means for determining and storing estimates of all possible emitter site locations associated with said set of DOA vectors, and where one of said estimates is a true emitter site location; (f) means for detecting the signal from the emitter again after the satellite has moved in its orbit relative to the emitter; (g) means for generating a new set of phase ambiguity integers; (h) means for adjusting the stored estimates of emitter site locations to account for the earth's rotation during satellite orbital movement; (i) means for predicting a new set of DOA vectors, utilizing the adjusted stored estimates a current satellite orbital position of the satellite; (j) means for predicting a new subset of ambiguity integers with each new DOA vector consistent with the orientation of said pair of antennas; (k) means for resolving the measured phase difference with each new ambiguity integer of said subset of ambiguity integers; (l) means for initializing a location estimator for each said DOA vector of said first set of DOA vectors; (m) means for inputting the respective resolved measured phase difference, means for updating each estimate of emitter site location, and means replacing each stored location estimate with a respective updated emitter site location estimate; (n) means for determining a probability or likelihood that one updated location estimate is the true emitter site location of said one emitter; and (o) means for generating an estimate of said true emitter site location based on the probability or likelihood determined in step (n).
※ AI-Helper는 부적절한 답변을 할 수 있습니다.