Coupling device for transponder and smart card with such device

Abstract

A coupling device is formed by a continuous conductive path having a central section and two extremity sections, the central section forming at least a small spiral for inductive coupling with the transponder device, the extremities sections forming each one large spiral for inductive coupling with the reader device, wherein the small spiral shows a larger pitch than the ones of the large spirals, and wherein the two extremities of the continuous path are loose such that the coupling device forms an open circuit. The pitches of the large spirals are chosen such as that the interturn stray capacitances is important and that the large spirals have mainly a capacitive behaviour. And the pitch of the small spiral is chosen such as that the interturn stray capacitances are negligible, and that the small spiral has mainly an inductive behaviour.

Dependencies are inferred from the claim text.