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

Abstract

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.