Active load modulation for contactless near-field communication

Abstract

To integrate NFC functionality in Smartphones and mobile, personal devices requires small loop antennas and specific constructions. For card mode operation there is a physical limit for the minimum antenna size to achieve standard conformance with conventional, passive load modulation. Active load modulation (ALM) can overcome this limitation and allows to construct very small antennas, but other problems arise to fit into existing infrastructure. We consider NFC antennas and present a new ALM concept in construction and function, which can overcome these problems, and we present first comparative results for the performance gain.