Eigenvalue Analysis of Close Coupled 13.56 MHz RFID-Labels

The technology of RFID (radio frequency identification) is on the way to change industrial processes but also our daily life significantly, as a variety of applications based on this technology are on the way to be implemented. While typical applications in the past had to handle only one tag/label in the field, future applications will have to face many labels in the field. In particular if they show a high coupling factor between them a severe detuning will occur, leading to a loss of functionality in the worst case. Examples for such scenarios may be smart shelfs were goods are equipped with RFID tags or identification cards, passports etc. carried close together. It is topic of this work to characterize the physical behavior of such close coupled systems in terms of effected resonance frequency and others. The influence will be characterized based on mathematical analysis - in particular an eigenvalue analysis. It will be pointed out that a solid mathematical understanding and modeling is absolutely necessary to handle future applications and to guarantee their functionality