Phase Center Offset Calibration and Multipoint Time Latency Determination for UWB Location

Abstract

The ultrawideband (UWB) system generates the precise Time of Arrival (TOA) to realize precise indoor positioning for various Internet of Things (IoT) applications. However, less attention has been paid to mitigating systematic errors in the UWB positioning algorithm, which could be a significant factor that reduces the positioning accuracy. The systematic errors are introduced mainly from two aspects. First, the offsets between the antenna reference point (ARP) and the real incidence point are not carefully eliminated from the ranging observations. Second, the between-antenna time latencies used for cable-linked synchronization usually contain systematic errors at the calibration point. In this article, we present two techniques, including the antenna phase center offset (PCO) calibration and the multipoint time latency determination (MTLD), to reduce the impact of systematic errors on the UWB positioning accuracy. The experiments are carried out in an indoor parking lot. The results show that the established PCO calibration model can correct the PCO errors by 70%. The accuracy of time latency determination is improved by 10% with MTLD and further by 44% with both MTLD and PCO calibration. The static and kinematic positioning tests indicate that the horizontal accuracy is improved from 31 to 10 cm and 20 to 10 cm, respectively.