Detecting a presence of near field communications (NFC) devices

摘要

A near field communications (NFC) device is disclosed that detects a presence of another NFC capable device within its magnetic field. The NFC device observes signal metrics of an observed detection signal at various intervals. The NFC device determines a statistical relationship based upon at least two first signal metrics from among the signal metrics to determine an estimate of at least one second signal metric from among the signal metrics. The NFC device compares a difference between the estimate of the signal metric of the at least one second signal metric and the at least one second signal metric. The NFC capable device makes a first determination that another NFC device is present within its magnetic field when the difference indicates that the at least one second signal metric is non-linearly related to the at least two first signal metrics.

主权项

1. A first near field communication (NFC) device, comprising:
a modulator configured to modulate a detection signal onto a carrier wave to provide a modulated detection sequence, the detection signal having a first power level for a first duration to provide a first interval, a second power level for a second duration to provide a second interval, and a third power level for a third duration to provide a third interval, the second power level being greater than the first power level; a demodulator configured to demodulate the modulated detection sequence to provide a recovered detection sequence; and a controller configured to:
determine a first signal metric of the recovered detection sequence corresponding to the first interval and a second signal metric of the recovered detection sequence corresponding to the second interval,estimate a signal metric estimate of the recovered detection sequence based upon a relationship between the first and the second signal metrics,determine a third signal metric of the recovered detection sequence corresponding to the third interval, anddetermine, based upon a difference between the third signal metric and the signal metric estimate, whether the third signal metric is non-linearly related to the first and the second signal metrics indicating that a second NFC device is present within a magnetic field of the first NFC device.