A Contactless Testing Method for Parasitic Capacitance of UHF RFID Tag

A contactless testing approach is proposed to evaluate the parasitic capacitance of ultra-high frequency(UHF) radio frequency identification (RFID) tag. The parasitic capacitance introduced when assembling the UHF RFID tag chip to the antenna results in performance deviation of the tag. This parasitic capacitance affects the accuracy of tag simulation design and leads to the detuning of the RFID tag. This paper presents the analysis of parasitic capacitance through theoretical derivation and experimental investigations. The method is established based on the equivalent circuit model of the UHF RFID tag and the expression of the parasitic capacitance. The measured results show that the simulated resonance frequency, taking into account the parasitic capacitance, closely matches the measured resonance frequency. This study can provide a valuable reference for the good design of the UHF RFID tag.