A system for sensing a proximity of a near field communication (NFC) device includes an NFC reader that communicates with a remote NFC device through load modulation. The NFC reader transmits a wireless carrier signal from an antenna, and the remote NFC device modulates the carrier signal by changing its internal impedance in order to transmit data to the NFC reader. The NFC reader has at least one antenna for receiving the modulated signal. The antenna is coupled to circuitry that analyzes the signal received from the remote NFC device The circuitry then identifies a resonant frequency for the remote NFC device based on the received signal and controls transmission characteristics of the NFC reader for communicating with the remote NFC device based on the identified resonant frequency.