Patent ID: 8718674

Claim:
A method for locating an emitter that transmits a signal toward a receiver, the receiver comprising N radio frequency receiving channels, where N is an integer equal to or greater than one, said signal being unknown to the receiver and said signal being reflected off a plurality P of reflectors of known positions, where P is an integer greater than one, the method comprising: performing multi-channel joint estimation and detection of time differences of arrival τ i and of frequency differences of arrival f i of each reflected path of said signal among a plurality of reflected paths off said plurality P of reflectors by: estimating an autocorrelation matrix R xx (τ,f) of the signal received by the receiver as a function of a time difference of arrival τ and a frequency difference of arrival f; constructing a normalized criterion using the formula: ĉ xx (τ,f)=1−det(I N −{circumflex over (R)} xx (0,0) −1 {circumflex over (R)} xx (τ,f){circumflex over (R)}(0,0) −1 {circumflex over (R)} xx (τ,f) H ), where det is a determinant of a matrix, I N is an identity matrix with N rows and N columns, and {circumflex over (R)} xx (τ,f) is an estimate of the autocorrelation matrix R xx (τ,f); calculating a detection threshold η ⁡ ( T , B ) = α ⁡ ( p fa , 2 ⁢ N 2 ) 2 ⁢ K , where K=B noise T, and where α(p fa ,2N 2 ) is determined by a table of chi-2 law for a probability p fa and a number of degrees of freedom equal to 2N 2 ; and determining a plurality P pairs (τ i ,f i ) that satisfy: ĉ xx (τ i ,f i )>η(T,B), where ĉ xx (τ i ,f i ) is a local maximum of a criterion ĉ xx (τ,f); performing angular estimation of an angular direction θ 1 of a direct path of the signal by a goniometry procedure; and determining a location, in two dimensions, of a position (x,y) of the emitter based on the plurality P of pairs (τ i ,f i ), or based on the plurality P of pairs (τ i ,f i ) and the angular direction θ 1 , by: plotting a plurality P of branches of hyperbolas based on the plurality P pairs estimated (τ i ,f i ) for each reflected path of said signal; plotting a straight line passing through the receiver and having as an angle of incidence said angular direction θ 1 ; and determining the position (x,y) of the emitter based on an intersection of at least two curves from among one or more of the plurality P branches of hyperbolas and the straight line.