High resolution localization of narrowband radio emitters based on doppler frequency shifts

The localization of stationary narrowband radio emitters using multiple moving receivers is considered. Most of the methods addressing this problem are based on two processing steps. In the first step, each receiver independently extracts signal measurements at several locations along its trajectory. Such measurements are the Doppler frequency shift or the frequency difference from a reference receiver. In the second step, these measurements are used for geolocation. On the other hand, the direct position determination method advocates using the observations from all the receivers together in order to estimate the location in a single step. This single-step method is known to outperform two-step methods when the signal to noise ratio is low. In this paper, we propose a direct-position-determination-based method for Doppler-based localization of multiple emitters that transmit unknown signals. The method can only be used for narrowband signals, namely, the signals' bandwidth must be small compared to the inverse of the propagation time between the receivers. The method does not require knowledge of the number of emitters. It is based on minimum-variance-distortionless-response considerations to achieve a high resolution estimator that requires only a two-dimensional search for planar geometry, and a three-dimensional search for the general case.