Near Field RF Commuincator

摘要

A near field Radio Frequency communicator 100 includes a demodulation circuit 114 whereby a clock signal can be derived 115 from a received RF signal in an active RFID tag during modulation from multiple sources using different operating voltages. Overvoltage from H-field signals inductively coupled to the antenna 102 is avoided via a shunt regulator 310 which controls the antenna's impedance load in accordance with the data signal 117, such that the RF voltage induced between the two antenna outputs is regulated below a maximum but remains above a minimum threshold voltage for deriving the clock signal when the device is in reception (target) mode. Controller 107 also prevents high voltages occurring when the device is in transmission (initiator) mode.