Compact Low-Profile Dual-Band Tag Antenna for Indoor Positioning Systems

A compact, dual-band, dual-port, and linearly polarized tag antenna is proposed for indoor positioning systems. It operates in both UHF and UWB bands, covering 881-913 MHz for the lower band and 2.9-5.35 GHz for the upper band. U-shaped planar inverted-F antenna for the UHF band is designed to surround the dipole for the UWB band so that both bands can share the same radiating aperture and a compact structure (100 × 50 × 9 mm
³
) is realized. In order to obtain a wideband and stable radiation performance in the upper band, a novel differential feeding structure is proposed to excite the ellipse-shaped dipole that exhibits good impulse performance. Meanwhile, the isolation between both ports is greatly improved to be better than 20 dB through loaded inductors. Measurements of a prototype show stable radiation patterns at both bands. With attractive features, this antenna can be potentially useful for indoor positioning systems.