Patent ID: 8838023

Claim:
A method of transmitting data by inductive coupling and active load modulation, the method comprising: receiving an antenna signal using an inductive antenna circuit in the presence of an alternating external magnetic field; extracting from the antenna signal a first periodic signal; producing a second periodic signal using a synchronous oscillator having a synchronization input receiving the first periodic signal, the synchronous oscillator having a synchronous oscillation mode set in phase with the first periodic signal and a free oscillation mode; applying to the antenna circuit bursts of the second periodic signal of a duration less than that of one bit of the transmitted data to generate an active load modulation magnetic field; placing the synchronous oscillator in the synchronous oscillation mode before each application of a burst of the second periodic signal to the antenna circuit; and placing the synchronous oscillator in the free oscillation mode during the application of a burst of the second periodic signal to the antenna circuit, such that the synchronous oscillator is resynchronized to the first periodic signal at least once at each transmission of a data bit.