Compact diversity antenna for UHF RFID readers

Abstract

A diversity antenna combining four inverted-F antennas (IFAs) is evaluated for UHF RF identification (RFID) readers. Polarisation and pattern diversities are obtained for a sequentially rotated configuration of the IFAs. Mutual coupling between ports is minimised by etching quarter-wavelength slots into the ground plane. The resulting envelope correlation coefficient is less than 0.003 in the working band. A switching diversity scheme is then applied to evaluate the tags readability in a lab environment. It is shown that the antenna diversity enhances the reading range compared to a circularly or a linearly polarised antenna of the same size.

Dual‐band RFID tag antenna based on the Hilbert‐curve fractal for HF and UHF applications

“…1 serves simultaneously two frequency bands, namely HF and UHF-bands. In contrast to the common RFID tags consisting of two individual antennas [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31], the proposed dual-band structure comprises a single radiator that operates in the HF and UHF-bands.…”

“…[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. Card-type dual-band RFID tags have also been demonstrated for positioning applications [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. In dual feeding port-type tags, the spiral coil and meander-line dipole are used as the HF antenna and the UHF antenna, respectively, where the meandered dipole antenna is located outside the HF coil [17].…”

“…Based on the card‐type dual‐band tags [17–31], and the series Hilbert‐curve tag [41], an alternative card‐type dual‐band RFID tag is proposed in this paper. The proposed tag merges the series Hilbert‐curve for HF coil antenna and square loop patch for UHF antenna to form a single radiator in order to obtain a compact tag with dual‐band performance.…”

“…Recently, the HF/UHF dual‐band RFID tags were introduced for various applications such as logistics, inventory management and bio‐engineering, etc. [16–31]. Card‐type dual‐band RFID tags have also been demonstrated for positioning applications [17–31].…”