Detection apparatus and method for near field communication devices
First Claim
1. A circuit for detecting the proximate location of an external communication circuit with a near field communication device, the circuit comprising:
- a communication coil configured for near field communication at a communication frequency;
a communication circuit coupled to the communication coil for transmitting data at the communication frequency, the communication circuit having at least a communication mode when transmitting data an idle mode when not communicating;
a control circuit;
a capacitor configured to be selectively coupled by the control circuit with the communication coil;
an oscillator, responsive to the control circuit, configured to selectively apply a probing signal to the communication coil at a probing frequency; and
a comparator coupled to the communication coil for sensing the probing signal across the capacitor;
wherein the control circuit is configured to couple the capacitor with the communication coil and to cause the oscillator to apply the probing signal when the communication circuit is in the idle mode;
wherein the comparator comprises an output coupled to the control circuit, the output configured to transition from a first state to a second state when a inductively coupled object is proximately located with the communication coil;
wherein the presence of an inductively coupled object causes the probing signal across the capacitor to change by at least a predetermined amount thereby indicating the presence of the inductively coupled object.
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Accused Products
Abstract
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.
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Citations
20 Claims
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1. A circuit for detecting the proximate location of an external communication circuit with a near field communication device, the circuit comprising:
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a communication coil configured for near field communication at a communication frequency; a communication circuit coupled to the communication coil for transmitting data at the communication frequency, the communication circuit having at least a communication mode when transmitting data an idle mode when not communicating; a control circuit; a capacitor configured to be selectively coupled by the control circuit with the communication coil; an oscillator, responsive to the control circuit, configured to selectively apply a probing signal to the communication coil at a probing frequency; and a comparator coupled to the communication coil for sensing the probing signal across the capacitor; wherein the control circuit is configured to couple the capacitor with the communication coil and to cause the oscillator to apply the probing signal when the communication circuit is in the idle mode; wherein the comparator comprises an output coupled to the control circuit, the output configured to transition from a first state to a second state when a inductively coupled object is proximately located with the communication coil; wherein the presence of an inductively coupled object causes the probing signal across the capacitor to change by at least a predetermined amount thereby indicating the presence of the inductively coupled object. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of detecting a presence of an inductively coupled object relative to a near field communication module, the method comprising the steps of:
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providing a communication coil configured for near field communication at a communication frequency when in a communication mode; providing a communication circuit coupled to the communication coil, wherein the communication circuit is capable of entering an idle mode when not communicating; causing the communication circuit to enter the idle mode; switching a capacitor in parallel with the communication coil; applying a probing signal at a probing frequency to the communication coil while the capacitor is coupled in parallel with the communication coil; and sensing the probing signal across the capacitance; wherein when the probing signal across the capacitance is below a predetermined threshold, switching the capacitor out of parallel with the communication coil and causing the communication circuit to exit the idle mode and enter the communication mode. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A portable electronic device, comprising:
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a near-field communication coil; a control circuit coupled to an oscillator, a comparator, and a capacitor, wherein the control circuit is configured to selectively couple the capacitor in parallel with the near field communication coil and to selectively actuate the oscillator at least at a probing frequency; and a near-field communication circuit, responsive to the control circuit, coupled to the near-field communication coil; wherein the control circuit couples the capacitor in parallel with the near-field communication coil and actuates the oscillator at the probing frequency when the control circuit is in an idle mode and not communicating; further wherein when an inductance associated with the near-field communication coil changes by more than a predetermined threshold as detected by the comparator, thereby indicating the presence of an inductively coupled object, the control circuit actuates the near-field communication circuit, enters a communication mode, and begins transmitting data. - View Dependent Claims (19, 20)
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Specification