PEEC modeling of circular spiral coils

In this contribution, we discuss a numerical model for a circular spiral coil based on the partial element equivalent circuit (PEEC) method and validate it by measurements. The numerical model includes skin and proximity effects. The main application, is a HF RFID standard antenna for 13.56 MHz. The numerical model is implemented in Matlab and we compare the results with those obtained by the HFSS simulation tool. The influence of the geometric parameters of the coil on the coil´s impedance is investigated in the frequency range 1-500 MHz. For verification of the numerical model, we produced two sets of coils, each consisting of 6 coils with varying geometric parameters. The most influential parameters on the impedance are the number of turns N, and radius a of a coil (i.e. class of a coil). When N is increased (or a) then the resonance frequency is decreased. Influence of other parameters turns out to be negligible.