A Null-Steering Antenna for Accurate Localization with the Internet of Things

This paper presents an antenna design for indoor positioning systems with the Internet of Things (IoT). The problem of direction-finding using a small array antenna with IoT devices is discussed. Theoretical studies clarify the limitations and challenges of using a null to estimate locations accurately and reduce antenna size and cost. Most importantly, electronic null-steering causes fluctuation in null-forming accuracy due to amplitude errors in the antennas and feeding circuits. This article experimentally demonstrates that this deviation error is suppressed using two copper wires and a suitable feeding circuit. The methods are feasible for practice as complicated corrections, such as amplitude controlling or signal processing, are excluded. The prototype steers a null with an angular resolution better than 4° within ${\pm} 60^{\circ}$, verifying the simulated results.