Direct power transmission load modulation in near field communication devices

摘要

An NFC initiator device requests a passive communication mode by modulating a request onto a first carrier signal. In response thereto, the target device transmits a second carrier signal while still receiving the first carrier signal from the initiator device. The target device may modulate data onto the second carrier signal to convey information to the initiator device. The initiator device may detect changes in the load provided by the target device to interpret the data conveyed by the target device.

主权项

1. A method of operating a near-field communication (NFC) device as a target device during an NFC session, the method comprising:
receiving a polling command from an initiator device requesting a passive communication mode for the NFC session; receiving a first carrier signal from the initiator device during the NFC session, the first carrier signal remaining un-modulated after the polling command is received; transmitting a second carrier signal from the target device to the initiator device while the first carrier signal is being received by the target device and remains un-modulated; and modulating data onto the second carrier signal, the first carrier signal and the second carrier signal combining to form a composite waveform indicative of the modulated data, wherein the composite waveform is a super-position of the first carrier signal and the second carrier signal.