Geolocation

Abstract

In selected embodiments, a process of geolocation of a transmitter uses a receiver with an antenna array that is non-line-of-sight (NLoS) to the transmitter. A first plurality of scatterers within line-of-sight (LoS) of the array is located using multilateration based on time difference of arrival (TDoA) from the first scatterers, and applying a spatial consistency requirement. Time of emission/reflection from the first scatterers is also determined. The coordinates and timing of the first scatterers are used to locate either the transmitter or another set of scatterers, by applying multilateration to the TDoA at the first scatterers, and applying the spatial consistency requirement. The process is iteratively repeated until the transmitter is identified. The multilateration may be linearized without sacrificing precision. In each iteration, a non-singularity requirement is applied to ensure that the selected scatterers produce unambiguous results.

What is claimed is: 
     
         1 . A process of geolocation of at least one radio frequency (RF) transmission source using a antenna array, the process comprising steps of:
 locating a first plurality of scatterers within line-of-sight (LoS) of the antenna array, wherein for each scatterer of the first plurality of scatterers coordinates and time of emission are estimated;   locating the at least one RF transmission source based on the coordinates and the times of emission estimated for the first plurality of scatterers, thereby obtaining coordinates of the at least one RF transmission source; and   providing the coordinates of the at least one RF transmission source, the step of providing comprising at least one of displaying, storing, and transmitting coordinates of the at least one RF transmission source.   
     
     
         2 . A process of geolocation according to  claim 1 , wherein the step for locating the first plurality of scatters is performed using (1) Spatial Consistency algorithm, and (2) multilateration based on time difference of arrival (TDoA) of signals at the antenna array. 
     
     
         3 . A process of geolocation according to  claim 2 , wherein the antenna array is located non-line-of-sight (NLoS) to the at least one RF transmission source, and wherein geolocation bias errors are reduced or eliminated. 
     
     
         4 . A process of geolocation according to  claim 3 , wherein at least one scatterer of the first plurality of scatterers is located non-line-of-sight to the at least one RF transmission source. 
     
     
         5 . A process of geolocation according to  claim 3 , wherein at least two scatterers of the first plurality of scatterers are located non-line-of-sight to the at least one RF transmission source. 
     
     
         6 . A process of geolocation according to  claim 3 , wherein each scatterer of the first plurality of scatterers is located non-line-of-sight to the at least one RF transmission source. 
     
     
         7 . A process of geolocation according to  claim 3 , wherein the step of locating the at least one RF transmission source comprises iteratively determining coordinates and times of emission at a next set of scatterers within LoS of a previous set of scatterers until coordinates of the at least one RF transmission source are determined, wherein the step of iteratively determining comprises applying the Spatial Consistency algorithm and multiateration based on TDoA at each iteration, and wherein the multilateration is linearized. 
     
     
         8 . A process of geolocation according to  claim 7 , wherein the step of locating the at least one RF transmission source comprises ensuring satisfaction of a non-singularity condition at said each iteration. 
     
     
         9 . A process of geolocation according to  claim 3 , wherein the at least one transmission source consists of a single RF transmission source. 
     
     
         10 . A process of geolocation according to  claim 3 , wherein the at least one transmission source comprises a plurality of RF transmission sources, and wherein coordinates of at least two RF transmission sources of the plurality of RF transmission sources are identified. 
     
     
         11 . A process of geolocation of one or more transmission sources in a non-line-of-sight (NLoS) path from at least one receiver with a plurality of antenna elements, comprising:
 geolocating scatterers that are line-of-sight (LoS) to the plurality of antenna elements;   after the step of geolocating the scatterers that are LoS to the plurality of antenna elements, using previously located scatterers as a virtual array to geolocate a next set of scatterers or the one or more transmission sources, the step of using the previously located scatterers being repeated until coordinates of the one or more transmission sources are obtained; and   at least one of displaying, storing, and transmitting the coordinates.   
     
     
         12 . A process of geolocation according to  claim 11 , wherein the step of geolocating the scatterers that are LoS comprises applying Spatial Consistency algorithm, performing multilateration based on time difference of arrival (TDoA) of signals, and selecting scatterers that satisfy a non-singularity condition. 
     
     
         13 . A geolocation system comprising:
 an antenna array comprising a plurality of antenna elements;   at least one receiver coupled to the antenna array and configured to receive signals from each antenna element of the array; and   at least one processor coupled to the at least one receiver to obtain information derived from the signals;   wherein the processor is configured to
 locate a first plurality of scatterers within line-of-sight (LoS) of the antenna array by estimating coordinates and time of emission for each scatterer of a first plurality of scatterers that scatter a signal transmitted by at least one non-line-of-sight (NLoS) radio frequency (RF) transmission source; 
 locate the at least one RF transmission source based on the coordinates and the times of emission estimated for the first plurality of scatterers, thereby obtaining coordinates of the at least one RF transmission source; and 
 provide the coordinates of the at least one RF transmission source by at least one of displaying, storing, and transmitting the coordinates of the at least one RF transmission source. 
   
     
     
         14 . A system according to  claim 13 , wherein the at least one processor is further configured to locate the first plurality of scatters using (1) Spatial Consistency algorithm, and (2) linearized multilateration based on time difference of arrival (TDoA) of signals at the antenna array. 
     
     
         15 . A system according to  claim 14 , wherein the at least one processor is configured to determine iteratively coordinates and times of emission at a next set of scatterers within LoS of a previous set of scatterers until the at least one RF transmission source is identified, by applying the Spatial Consistency algorithm and multilateration based on TDoA at each iteration, and wherein the multilateration is linearized. 
     
     
         16 . A system according to  claim 15 , wherein the at least one processor is further configured to ensure satisfaction of a non-singularity condition at each iteration. 
     
     
         17 . An article of manufacture comprising machine-readable storage medium with program code stored in the medium in a non-volatile manner, the program code, when executed by at least one processor of a system comprising an antenna array with a plurality of antenna elements, at least one receiver coupled to the antenna array, and at least one processor coupled to the at least one receiver, configures the system to:
 locate a first plurality of scatterers within line-of-sight (LoS) of the antenna array, wherein for each scatterer of the first plurality of scatterers coordinates and time of emission are estimated;   locate the at least one RF transmission source based on the coordinates and the times of emission estimated for the first plurality of scatterers, thereby obtaining coordinates of the at least one RF transmission source; and   provide the coordinates of the at least one RF transmission source by at least one of displaying, storing, and transmitting the coordinates of the at least one RF transmission source.