Low-cost circularly polarized conical beam RFID antenna for indoor access point integration

This paper presents a low-cost circularly polarized conical-beam RFID antenna designed for integration with indoor access points. The antenna consists of two FR-4 PCB layers, where the lower layer represents the access point PCB and serves as the ground plane and mechanical support of the RFID antenna, while the upper layer contains horizontal radiating elements that excite the TM02 mode to generate the conical radiation pattern. Radial meandered feed lines provide in-phase excitation to perimeter radiating arcs, enabling a compact structure. Four central screws connecting two PCBs also act as conductive RF pins, carrying vertical current flows. The resulting circular polarization achieves an axial ratio below 3 dB across the entire 920 – 925 MHz RFID band. The simulated results demonstrate a realized gain above 1 dBi and a radiation efficiency of approximately 75%, making it suitable for cost-effective indoor RFID applications.