RFID antennas for the UHF remote monitoring of human subjects

Abstract—This paper addresses the design of passive and semi-passive transponder antennas for radio frequency identification applications involving the human body as the object to be tagged or bio-monitored. A planar tag antenna geometry, that is based on a suspended patch fed via a nested slot and is able to host sensors and electronics, is here introduced. Guidelines for conjugate impedance matching are given for different kinds of microchip transmitters, within power limitations as well as space constraints. Finally, the antenna matching performance is experimentally evaluated uti-lizing a body-tissue phantom. Index Terms—Impedance matching, planar antenna, radio fre-quency identification (RFID), sensor networks, slot antenna. I