A compact platform-tolerant antenna for RFID tag with stable gain

A low-profile ultra high frequency (UHF) radio frequency identification (RFID) tag antenna is proposed with a compact size of 80 × 30mm² and stable gain while attaching on different mediums. The antenna is composed of a quarter-wave length patch etching on FR4 substrate and a suspended inductively coupling loop who connected with a RFID chip. The antenna acts as an omnidirectional electric monopole antenna and directional aperture antenna while mounted on dielectric and conductor platforms respectively. Antenna gain at the normal direction of antenna surface (θ = 0°,φ = 0°) fluctuates less than 2dB with peak value 0dBi while the antenna is mounted on different mediums, resulting a unique long reading distance under different application scenarios.