DoA Estimation With a Single Antenna and a Few Low-Cost Backscattering Tags

Backscatter radio utilizes the reflection that an electromagnetic wave undergoes when it impinges an unmatched-to-a-load antenna, in order to achieve ultra-low-power communication. This work exploits principles commonly found in the ultra-low-power, backscatter communication literature, offering multi-element array functionalities to a single-antenna receiver. A small number of simple, switching backscattering tags deployed in space, emulate a distributed, multi-element antenna array by copying a transmitter’s signal to distinct frequency bands. A receiver can then obtain independent observations of the same signal by discriminating said bands. Using the backscatter tag-based array, the direction of arrival (DoA) estimation problem is addressed without the cost of multiple RF front ends or hardware modifications, at either end of a wireless communication link. The feasibility of the idea was examined through both simulations and experimental deployments. An absolute error of
$\approx 20$
degrees was observed when utilizing 5 custom-built backscattering tags, while simulations showed that more than 10 tags can offer error of less than 5 degrees.