| 摘要 |
A method of locating the source of an unknown signal. The method comprises the steps of:(i) calculating a differential offset for a signal for each of a plurality of positions within a region in which the transmitter must lie, for each of a series of times m with respect to first and second signal relays and respective first and second receivers, the positions of the signal relays and receivers being known; (ii) generating a cross-ambiguity function (CAF) using data corresponding to samples of the unknown signal received at the first and second receivers via the first and second signal relays respectively,(iii) estimating the level of noise on the CAF; and(iv) using data generated in steps (i), (ii) and (iii) to obtain a measure of the likelihood that the source is located within defined areas within said region, wherein the differential offsets are differential time offsets (DTOs), or differential frequency offsets (DFOs), or both DTOs and DFOs. The method further comprises the steps of (v) for each of a series of times m, sampling the unknown signal at first and second receivers via first and second signal relays respectively; (vi) generating a corresponding series of m CAF surfaces; (vii) for a given latitude ± and longitude ² , computing differential time and frequency offsets DTO m , DFO m , at each time m , finding the associated CAF surface value CAF m at each time m , and corresponding values SNR m of signal-to-noise ratio; and (viii) evaluating the chi-squared value Ç 2 ± �¢ ² = Ç min 2 - 2 ln �¢ 1 - P |
