Hemispheric coverage multi-beam switched antenna array using a 4-port feeding network for UHF RFID dead zone avoidance

For ultra-high frequency (UHF) radio frequency identification (RFID) dead zone avoidance from the viewpoint of antenna configurations and radiation characteristics, a hemispheric coverage mutli-beam switched square quadrifilar spiral antenna (QSA) array using a 4-port feeding network is presented. The proposed antenna array consists of a 2×2 circular polarized QSA array and a 4-port feeding network for multiple beams. It generates single-, dual-, and quad-beams with a hemispheric coverage by a beam switching, and its maximum beam gains and directions are 7.4 dBic and 65°, respectively. By switching multi-beams with the hemispheric coverage, the proposed 2×2 QSA array with a 4-port feeding network improves the tag identification in the dead-zone read area within the reading range.