A Hybrid TDOA/RSSD Geolocation System Using the Unscented Kalman Filter

Geolocation is an important topic nowadays. Among other applications, geolocation can be used by frequency regulators to monitor the time, frequency and space domain. In this case of a passive geolocation system, Time Difference of Arrival (TDOA) is often used. In this paper we analyze a geolocation system based on a combination of TDOA and Received Signal Strength Differences (RSSD). The benefit of combining the two measurement types is shown using the Cramer Rao Lower Bound (CRLB). The suitability of the Unscented Kalman Filter (UKF) as an algorithm for the hybrid geolocation system is investigated. Simulation results show that by using the UKF, the instability of RSSD geolocation, that is often caused by bad geometry, is compensated. The UKF nearly approaches the CRLB and greatly outperforms the previously proposed least squares hybrid solution. Using the UKF, the information about the signal power can be definitely used to enhance the position estimation accuracy.