Estimating radar positions using cooperative unmanned air vehicle teams

Standard TDOA (time-difference of arrival) estimation techniques are modified and applied to locate networked enemy radars using a cooperative team of unmanned electronic combat air vehicles (ECAVs). The team is engaged in deceiving the radars, which limits where the ECAVs can fly and requires accurate radar positions to be known. Two TDOA measurements of radar pulses taken by two ECAV pairs are used to estimate the position of the middle radar. A nonlinear system model for estimation is formulated and used to perform simulations with "noisy" TDOAs; a linearized time-varying model for straight nominal ECAV trajectories is derived from the nonlinear model. The choice of optimal ECAV trajectories and an observer to minimize the variance of the middle radar position - using the linearized model is addressed. Application of a time-varying Kalman filter to the linearized system shows drastic improvement in reducing the variance of position estimates when compared to the original nonlinear system via simulations.