RFID Antennas for the UHF Remote Monitoring of Human Subjects

Abstract

Abstract-This paper addresses the design of passive and semipassive 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 utilizing a body-tissue phantom.Index Terms-Impedance matching, planar antenna, radio frequency identification (RFID), sensor networks, slot antenna.

Meandered-Slot Antennas for Sensor-RFID Tags

“…The choice of the slot, as main radiating element, is expected to simplify the synthesis of the inductive reactance required to match the generally capacitive IC's impedance. As discussed in [4], the H-slot may radiate, depending on the slot's aspect ratio, as a broadband patch, a doubly folded dipole or as a dumbbell slot.…”

“…(3) where is a safeguard distance from the patch edges. The fitness function to maximize is (4) where are the frequencies at which the RFID should be best matched to the chip, and are arbitrary weights. The optimization problem is solved using a Genetic Algorithm (GA) [7] procedure, already successfully applied to meander-line tag design [8].…”

“…The performance of the GA-optimized multitooth antennas can be appreciated in comparison with those of the simple H-shaped slot (single tooth, ) described in [4]. Fig.…”

“…In a recent paper [4], a versatile tag antenna configuration, having impedance tuning capability and the possibility to host electronics packaging, has been proposed for application in biomonitoring. The antenna consists of a nested H-slot suspended patch, wherein the external size determines the maximum gain while the H-aspect ratio affects the complex impedance matching.…”

Conformal Magnetic Composite RFID for Wearable RF and Bio-Monitoring Applications

“…The technology for RFID systems continuously improves and extends to structures of nonplanar shapes and to conformal sensors for wireless body-area networks (WBANs) [3]. Also, there is an increased demand for miniaturization, potentially addressed by the choice of substrate material, particularly magnetic materials [4].…”