Near field rf communications

摘要

A near field RF communicator comprises an inductive coupler 200 that couples with an RF H-field to provide an RF voltage signal; and a regulator having a voltage controlled impedance 703 coupled to the inductive coupler to attenuate the RF voltage signal to provide an output voltage; and a controller 702 to control the voltage controlled impedance such that the output voltage does not exceed a reference voltage and switches it into a non-conducting state in the event that the received RF voltage is less than the output voltage. The voltage controlled impedance can be connected between the input and output of a series regulator of a received voltage and its operation modified if the input voltage is less than the output voltage to provide a rectified output voltage. The regulator can be a series regulator such as a low dropout regulator. The communicator can comprise a switchable impedance 722 in parallel with the inductive coupler that the controller switched into a conducting state when the regulator voltage controlled impedance is switched to a non-conducting state. The voltage controlled impedance can be an IGFET such as a MOS transistor and the controller comprise a class AB amplifier. The near field communicator can be a NFC communicator and comprise a long range communication interface.