Miniaturized UHF/UWB Tag Antenna for Indoor Positioning Systems

A miniaturized ultrahigh frequency (UHF)/ultra-wideband (UWB) dual-band tag antenna with a geometrical dimension of 34.6 mm × 21.5 mm × 6 mm is presented for indoor real-time positioning systems. A small patch is employed as the UWB radiator, and two U-shaped striplines are used for the UHF band. A quarter-wavelength metallic strip is introduced under the UWB patch to create an extra resonance to further expand the operation bandwidth. The antenna is backed by a ground plane to reduce the backside radiation and to improve the antenna gain in the UWB band. The measured bandwidth covers the frequency range from 919 to 931 MHz in the UHF band and 3.28 to 6.95 GHz in the UWB band with VSWR better than 2:1. The measured radiation patterns within the above-mentioned UHF and UWB frequency bands are very stable. The attractive features of compact size and wide bandwidth make it a very competitive candidate of tag antenna for indoor positioning systems.