Dual-Band Shared-Aperture UHF/UWB RFID Reader Antenna of Circular Polarization

摘要

A dual-port, dual-band, and circularly polarized (CP) radio frequency identification reader antenna is designed to operate at both ultrahigh frequency (UHF) and lower ultra-wideband (UWB) bands for indoor positioning systems. In conjunction with a properly selected quadruple feed network, a shared aperture using the concept of hybrid mode is utilized for broadening the antenna bandwidth. The concept is demonstrated to achieve a high gain, wideband, and CP operation within a low profile. The measured overlapping 3-dB axis ratio (AR) bandwidth and 10-dB impedance bandwidth for the UHF band ranges from 0.918 to 0.926 GHz with a minimum in-band antenna gain of 9 dBic. The measured overlapping 3-dB AR bandwidth and 10-dB impedance bandwidth covers from 3 to 5.2 GHz with a minimum in-band gain of 9 dBic in the lower UWB band (i.e., 3.1-4.8 GHz). The gain suppression near the two wireless local area network bands (i.e., 2.45 and 5.8 GHz) is more than 20 dB. The isolation between two ports is larger than 25 dB over the UHF and lower UWB bands, respectively.