RF transmitter geolocation based on signal periodicity: Concept and implementation

We propose a novel technique to localize a periodic transmitter using a single mobile receiver. By having the receiver measure the time-of-arrival (TOA) of the periodic messages sent by the transmitter, the receiver is able to measure the virtual time-difference-of-arrival (V-TDOA) between different locations along its trajectory. The V-TDOA can then be used in place of TDOA measurements in various TDOA-based localization methods for the transmitter. However, a major challenge in obtaining an accurate V-TDOA measurement lies in separating it from the time offset between the transmitter and the receiver caused by the local oscillator (LO) drift. We propose a two-stage technique: in a first stage, the receiver stands still and uses the TOA measurements to train a Kalman filter to estimate and predict the LO skew between itself and the transmitter. In a second stage, the receiver starts moving and uses its prediction of the LO skew to estimate the V-TDOA. The proposed algorithm is implemented on a software-defined radio testbed, and experimental results show that our setup is able to successfully measure the V-TDOA.