Patent ID: 6985107

Claim:
A method for locating one or more transmitters within a search area using an array of antennas, the one or more transmitters transmitting signals having the same carrier frequency, and the array of antennas operating on a common clock signal, the method comprising the following steps: (a) specification of a grid of possible grid point locations covering the search area, adjacent grid point locations being a distance equal to a predetermined fraction of the wavelength of the carrier frequency apart, said predetermined fraction being less than or equal to ⅛; (b) establishment of a library of manifold vectors, one for each grid point location, describing the phase interrelationships between a hypothetical carrier frequency signal emanating from said grid point location and the signal as received by all antennas; (c) reception and digitization of one or more signals by the array of antennas to determine snapshot vectors containing phase angles of arrival information for the one or more signals at each antenna; (d) computation of a covariance matrix for the snapshot vectors over all antennas; (e) combination of the covariance matrix or a submatrix thereof with each manifold vector in the library to create a virtual interference pattern for the one or more signals; and (f) selection as possible locations for the transmitters those grid point locations where the associated value of the virtual interference pattern exhibits a maximum value, and exceeds a threshold representing a null hypothesis; whereby the possible locations for the transmitters have a precision of ¼ wavelength.