Mathematical Analysis of Parasitic Elements Influence in Resonant Circuit of RFID Antenna

In this paper a mathematical analysis of parasitic elements (parasitic inter-winding capacitance and loss resistance of inductor, internal resistance of generator) influence on serial resonant circuit is described, because such circuit is often being used as a reader antenna for LF and HF band RFID application. The influence of the parasitic elements on the coil current is analytically investigated. The equations for calculation of optimum value of the antenna tuning capacities and for calculation of the antenna resonant frequencies are derived.