Compact 3-D-printed circularly polarized antenna for handheld UHF RFID Readers

In this letter, the aptness of the combination of three-dimensional (3-D) printing and radio frequency identification (RFID) is faced by presenting a compact, low-profile, and cost-effective circularly polarized antenna for handheld UHF RFID reader. The radiating element has been realized through a circular array of four inverted-F monopoles, where the array elements are excited with a 90° phase offset through a microstrip feeding network, realized in 3-D printing technology as well. Taking advantage from low losses and moldability of the 3-D printing materials joint to a specific design strategy, the proposed antenna realizes an improved gain and an appreciable size reduction if compared with the state of the art.