A Dual-feed Antenna for Passive UHF RFID Tag-based Sensor Applications

A low-cost passive UHF RFID tag-based sensor is presented. The proposed tag-based sensor comprises a dual-feed patch antenna incorporated with passive sensor and passive RFID chips operating at UHF RFID bands. By introducing the passive sensor (i.e. resistive sensor nodes) in one of the tag antenna feed, low-cost wireless nodes with radio frequency identification and sensing capabilities are implemented. To remotely record the sensed data at any arbitrary distance from the reader, the other feed of the tag antenna is incorporated with only RFID chip and it serves as a reference node. By measuring the difference of the required minimum power transmitted by the reader to wake-up the RFID chips in both the reference and sensor nodes, the reader then can extract the sensed data (i.e. temperature) at the tag location.