Compact circularly polarized cross dipole antenna for RFID handheld readers/IoT applications

The radio frequency identification (RFID) and global positioning system (GPS) are employed for indoor and outdoor tracking scenarios. This paper presents an amalgamated identification mechanism for sensing and tracking in an Internet of things (IoT) network. A low-profile, compact, multi-functional antenna configuration is proposed for the amalgamation application. The antenna operates in the 915 MHz (UHF), 2.45 GHz, and 5.8 GHz RFID bands, along with the 1.575 GHz GPS L1 band. The presented antenna is a cross dipole configuration consisting of three pairs of dipole elements printed on both sides of the dielectric substrate. The first and third dipole pairs are larger and smaller metal strips with half-arrow shaped ends that excite the 915 MHz and 5.8 GHz bands, respectively. The second dipole pair is an asymmetric triangular-shaped radiator that excites the 1.575 GHz and 2.45 GHz bands. Using quarter wavelength ring delay lines, circular polarization is obtained in each band. The GPS band, in combination with the RFID bands, improves the efficiency and accuracy of the reader tracking device. The proposed multiband antenna prototype is fabricated on the 45 degrees rotated substrate material, resulting in a compact size of 0.2120 x 0.2120 x 0.00420. The antenna simulation and measurement results are in close agreement.