Direct geolocation of wideband emitters based on delay and doppler

The localization of a stationary transmitter using receivers mounted on fast moving platforms is considered. It is assumed that the transmitted radio signal is random with known statistics. The conventional approach is based on two steps. In the first step the time difference of arrival and the differential Doppler shift are measured and in the second step these measurements are used for geolocation. We advocate a direct position determination approach that proves to be more computationally efficient and more precise for weak signals than the conventional approach. The direct method is a single-step method that uses the same signals as the two-step approach but searches directly for the emitter position without first estimating intermediate parameters such as Doppler frequency and the time delay. A secondary but important result is a derivation of closed-form and compact expressions of the Cramér-Rao lower bound. All results are verified by Monte Carlo computer simulations.