Dual-Port Folded Dipole Antenna for Harmonic RFID Over Metallic Surfaces

This paper presents a dual-port folded dipole antenna for harmonic radio frequency identification (RFID) over metallic surfaces such as a railway line. The antenna operates at 433 MHz and 866 MHz, which are the two RFID frequencies in Europe. The antenna is designed to be integrated with the metal object itself, using a via to connect the top layer with the ground plane. The antenna is made of FR-4 laminate, a common material for printed circuit boards, which provides good electrical and mechanical performance at a low cost. The antenna design parameters and components are described in detail, along with the simulated results and built prototype. The antenna presents 2.75 and 5.5 dBi of gain for 433 and 866 MHz respectively.