Joint Direct Estimation of Emitter Location and Antenna Beam Direction Based on Baseband Reconstruction

This article addresses the problem of locating a stationary noncooperative emitter using multiple moving receivers. A signal baseband reconstruction-based algorithm is proposed to locate the emitter directly from the received signals, without assuming static delay and Doppler shift in any observing interval. Besides the information of time difference of arrival (TDOA) and frequency difference of arrival (FDOA), the received signal strength (RSS) information is further utilized when the source emits signals in free space with an omni antenna. In a more complex scenario where the emitter adopts a directional antenna, an iterative algorithm is proposed to jointly estimate the emitter location and its antenna beam direction, where a traditional direct position determination (DPD) method is used to initiate the iteration. The Cramér–Rao lower bounds (CRLBs) of the emitter position and the beam direction are derived. Three numerical cases are included to investigate the performance of the proposed algorithms. The signal baseband reconstruction-based DPD algorithm shows improved applicability when the assumption of static time delay and Doppler shift is inappropriate and performs similarly to the classical DPD methods when the assumption holds. In the case of free-space propagation, it shows that the localization accuracy can be improved when RSS is further utilized. When the transmitting beam is directional, however, simply ignoring the directivity characteristics would lead to nonnegligible localization biases. By jointly estimating the emitter location and antenna beam direction, the RSS information can be effectively utilized to improve the localization accuracy, and a much more accurate estimation of beam direction can be obtained simultaneously.