Contactless communication method with negative modulation

摘要

The method involves applying a modulation rate greater than 100 percent to cause negative modulation. A carrier frequency (Fc) is generated or extracted by a portable contactless object (PICC), where the frequency is synchronous with interrogation frequency of a reader. The negative modulation is used during half-cycle part of a modulation signal, and a transponder object generates the modulation signal timed at a subcarrier frequency, where modulation generates sidebands and application of the signal causes amplitude modulation with level close to zero. The object is a secure digital card. An independent claim is also included for a contactless communication circuit for establishing communication between a contactless transponder and a reader.