Fine-scale tracking by fusing phase profiles from multiple low-power Doppler radars

Using phase information from medium bandwidth Doppler Radars, it is possible to obtain motion information corresponding to changes in target range on the order of a wavelength. Comparable range resolution from ranging radars would require much wider bandwidth. For long-range radars, the power consumption depends mostly on transmitted power levels and only weakly on bandwidth. But for short range radars of the type that are most useful in Wireless Sensor Networks (WSNs), transmitted power is usually negligible compared to processing power (i.e., within the radar), and the power budget depends strongly on the bandwidth. Thus, medium-bandwidth Doppler Radars offer the opportunity to achieve finer resolution of relative range information at much lower power at the expense of absolute range information.

This demonstration shows that by fusing the relative range profiles from multiple radars it is possible (with acceptable error rates) to construct the absolute trajectory, with sub-centimeter accuracy. Our problem formulation is a bit novel and results in a different computational approach, but the result is conceptually equivalent to creating a velocity-only tracker that uses velocity profiles (i.e., with respect to time) from several different vantage points.

Our primary contribution is demonstrating that this can be applied to low power mote-scale sensors. We show a pendulum swinging in the middle of three short range Doppler Radars, which are connected to TelosB motes that are connected to a laptop, on which an estimate of the current location and the recent track of the pendulum is shown with about 100 millisecond delay.