Near field communication enabled device with improved electromagnetic compatibility and a method of load modulating in near field communication

摘要

A near field communication (NFC) initiator communicates with a target device. The carrier is modulated to transmit a digital signal. During time slots allocated for target communication, the field is load modulated by the target. The target load modulator is driven by a digital modulator to vary voltage at antenna terminals so that peak amplitude of the carrier varies for specified periods between high and low values. To alleviate interference in the target device caused by the generation of aliases during transition, the load modulator sequentially applies a range of resistances to vary the amplitude (voltage) during transition according to a specific waveform determined by the infinite impulse response of a low pass filter tuned to the cut of frequency and sampling frequency determined according to the coexistence and cohabitation specifications of a chip in which the NFC functionality is embedded.