Influence of the real UWB antennas on the AoA estimation based on the TDoA localization technique

Main contribution of this paper is to present the influence of the real ultra-wideband directional antennas on the Angle of Arrival estimation. Furthermore, is to mitigate this undesired impact of the ultra-wideband antennas to improve the overall system performance and enhance the Angle of Arrival estimation accuracy. In the first step we analyze the estimation error due to the antenna induced delay if Vivaldi antennas are used as receiving antennas within two different scenarios. In the second step we present the corrected AoA estimation after mitigation of the error resulting from the antenna induced delay. The Angle of Arrival estimations with error mitigation and without error mitigation are compared. Real measurements are used in the experiments.

1 Introduction

Ultra-wideband (UWB) technology together with Time of Flight (ToF) based localization techniques are often used to realize indoor positioning systems. Huge bandwidth of UWB signals results in fine time resolution allowing precise time estimations even in indoor environment [1], [2], where severe multipath propagation is present. An important part of UWB based localization systems are the utilized antennas. UWB antennas often lead to significant signal distortions [3], which generally is also Angle of Arrival (AoA) dependent affecting a communication system or resulting in ToF estimation errors. As will be illustrated in this paper this antenna induced error can lead to a significant impact on the performance of the system, which is critical for special cases of TDoA based AoA estimation technique with closely spaced receiving antennas. Only the case of Line of Sight (LoS) is considered in the paper. It is also assumed that reflections can be separated from the direct signal path (DP), which is often assumed in UWB-based localization.