IQ signal based RFID sensors for defect detection and characterisation

Radio frequency identification (RFID) sensor systems have unique advantages of identification, communication and sensing together. Previous researches on RFID based sensing investigate power based features, and face the challenges of low sensitivity and robustness due to environment RF field. In this paper, rather than using received signal strength indicator (RSSI), we present a method using features of transient responses from in-phase quadrature (IQ) signal to overcome the challenges of sensitivity and robustness in ultra-high frequency (UHF) RFID sensor systems. The transient responses of the IQ signal are analysed using skewness feature for different defects. The experimental results show that IQ based skewness features from IQ signal improve sensitivity and robustness for defect characterisation compared with previous RSSI and RCS methods.