Modelling of free-running clocks for a virtually synchronized microwave locating system

For a microwave locating system virtual synchronisation of low-cost free-running transmitter clocks is proposed. The synchronisation strategy is based on modelling the transmitter clocks. A stable stochastic model was designed by analysing the correlation function of the observables in the locating system i.e. time of arrival and carrier phase. Exploiting this model in a Kalman filter, a reference receiver estimates the current clock states and distributes them periodically to the mobile receivers enabling them to predict the transmitter clock deviations between updates. The impact of this synchronization scheme on the position accuracy using both simulated and real data is analysed.