Respiration Monitoring using Doppler-Modulated Depolarizing Chipless Tags

This paper demonstrates that chipless RFID tags in the depolarizing configuration can be utilized to effectively monitor the human respiration rate and to identify the human subject. The cross-polarized backscattered field from the tag can be isolated from the co-polarized contribution of the human body and the background environment which facilitate the detection and identification process. The measurement principle is also based on the micro-Doppler effect: due to breathing, the movement of the chipless tag modulates the backscattered signal and this modulation is recovered at the reader over large distances. The idea is proved experimentally with measurements done on a human subject in a real environment. The respiration monitoring and the subject identification are achieved at up to 1.8 m read range.