Patent attributes
A near-field communication circuit (100), such as a radio frequency identification circuit, includes a communication coil (104) and a communication circuit (108) configured to transmit data (109) through the communication coil (104). When the communication circuit (108) is in an idle mode, probing circuitry (124) is configured to detect the presence of a magnetically conductive object within close proximity of a communication coil (104). In one embodiment, a control circuit (110) selectively couples a capacitance (125) in parallel with the communication coil (104). The control circuit (110) then applies a probing signal (116) to the communication coil (104). A comparator (118) monitors a secondary parameter of the communication coil (104), such as inductance or impedance. When a magnetically conductive object is detected, the communication circuit (108) transitions to a communication state and attempts to communicate with the object.
