Indoor Positioning with a Six-Beam Planar Antenna Suitable for 2.45 GHz Wireless Communications

In this paper, we propose a novel wireless anchor node architecture for positioning estimations in indoor scenarios. The node is equipped with a planar switched beam circular polarized antenna (SBA) optimized for operation at 2.45 GHz and operates with a System-on-Chip compliant with IEEE 802.15.4 communications radio technology. The antenna consists in two concentric patches printed on a low cost and low profile single-layer via-less substrate. The SBA is inherently capable of radiating six uncorrelated beams spanning over a semi-spherical range, by using a digitally controlled beamformer consisting of a pair of switches and a phase shifter. The use of the proposed device in conjunction with a Maximum-Likelihood algorithm leads to fine grained indoor positioning and tracking, reporting a mean error respectively of 10.9 degree and 10.2 degree for the θ and ϕ anale.