Direct detection and position determination of multiple sources with intermittent emission

This paper investigates the direct position determination (DPD) problem from passive measurements made with a moving antenna array in the case of a time-varying number of emitting sources. We derive the Cramér-Rao bound (CRB) for the estimation problem and find an approximation that is applicable for a large number of observations. We use different DPD approaches to solve the estimation problem. Therein, all source positions are estimated directly from a single cost function that results from fusing all measurements. The considered DPD approaches are based on Capon's method and the maximum likelihood (ML) estimation. The ML approach offers a superior performance compared to the Capon-type approach, but leads to a high-dimensional optimization. We use the alternating projection technique to solve the high-dimensional optimization by a sequence of low-dimensional optimizations. Finally, we propose an iterative direct detection and position determination (DDPD) approach that combines the aforementioned DPD and the determination of the total number of sources (commonly called detection), because the total number of sources is typically unknown. We present simulation results that demonstrate the performance of the DDPD approach.