High-Gain 3-D RFID Reader Antenna with Cubic Metasurface Backing and 360° Coverage for Internet of Vehicles

A high-gain antenna with wide coverage is required for the reader to identify and communicate with multiple vehicles at the same time. In this paper, a circularly polarized cubic metasurface-based array (CMSA) antenna is proposed for RFID readers used in vehicular-to-infrastructure communication. The proposed antenna consists of five cross-dipole elements mounted on a cubic metabox (CMB). Each surface of the CMB is a layer of artificial magnetic conductor (AMC) array of 3 × 3 unit cells, where each unit cell generates in-phase reflection for the UHF band. The presented AMC-backed antenna element has an impedance bandwidth of 810–920 MHz in the UHF band and 2.35–2.5 GHz in the WLAN band. The peak gain of the AMC-backed antenna element in the UHF and WLAN bands is 7 dB and 6.33 dB, respectively. Peak gain enhancements result in a longer reading range but narrow coverage. Therefore, a 3-D arrangement is used to widen the interrogation zone of the reader, resulting in a 360° coverage. The inter-element isolation is greater than 15 dB, and the envelope correlation coefficient is less than 0.006. The proposed CMSA antenna has a hollow cubic design, allowing it to accommodate the electronic circuitry of the reader. The proposed CMSA antenna could be a suitable candidate for readers used for tagged-vehicle detection due to its high gain, wide reading zone, dual-band coverage, low cost, low inter-element coupling, and ease of packaging.