Radio frequency Echo mapping with cellular devices

In this paper, a method is presented that employs portable cellular devices to perform three-dimensional localization of metallic objects from a set of time-delayed signals. These signals are observed by an array of receiving elements having arbitrary and a priori known distributions in space. Widely used solutions for direction finding are based on Time of Arrival (TOA) measurements. The measurement accuracy is strongly dependent on several system and scenario parameters, such as the target relative distance, number of received elements, distances between elements, azimuth and elevation beam-widths, all of which may cause ambiguity and multi-path effects. It is important that operational systems are capable of working with both static and moving targets. A recent solution involves obtaining Time Difference of Arrival (TDOA) measurements. To improve the accuracy of the measurements, a Delta Delta Phase (DDPhase) technique is herein proposed. It is suitable for even slow-moving targets, such as the one used in this study. Experimental results showed that the presented solution is feasible and with an accuracy of up to 0.3m for detecting targets, including those occluded behind a concrete wall.