How to guarantee phase-synchronicity in active load modulation for NFC and proximity

The introduction of Near Field Communication increases the application domain of RFID systems operating in the 13.56 MHz frequency domain significantly. Especially the environment within a Smartphone or a mobile device makes great demands on the physical characteristics of proximity coupling systems. Recently active load modulation was introduced to overcome the limitations using passive load modulation. However, with this new technology the problem of phase-synchronicity arises. Therefore, contactless Card phase drift test methods have to be developed to guarantee interoperability. This paper discusses the problem of phase synchronicity and analyses the appropriateness of the contactless test set-up. Moreover, we present an algorithm which allows to measure the phase drift accurately and compare results to a proposed algorithm. We will show that our algorithm significantly outperforms the other proposal in terms of phase drift measurement accuracy.