Device detection in contactless communication systems

• US 10,511,347 B2
• Filed: 11/14/2017
• Issued: 12/17/2019
• Est. Priority Date: 11/14/2017
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Hueber, Gernot, Macnamara, Ian Thomas
• Primary Examiner(s): Miller, Brian E
• Application Number:
  US15/812,200
• Publication Number:
  US 20190149196A1
• Time in Patent Office: 763 Days
• CPC Class Codes: G06K 7/10128 the step consisting of detection of the presence of one or more record carriers in the vicinity of the interrogation device
• CPC Class Codes: G06K 7/10297 arrangements for handling protocols designed for non-contact record carriers such as RFIDs NFCs, e.g. ISO/IEC 14443 and 18092 cryptographic protocols H04L9/00; network security protocols H04L63/00; real-time communication protocols in data switching networks H04L65/00; network protocols for data switching network services H04L67/00
• CPC Class Codes: G06K 7/10316 using at least one antenna particularly designed for interrogating the wireless record carriers antennas in general H01Q1/22
• CPC Class Codes: H03B 5/06 Modifications of generator to ensure starting of oscillations
• CPC Class Codes: H03B 5/1203 the amplifier being a single transistor
• CPC Class Codes: H03B 5/1228 the amplifier comprising one or more field effect transistors
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/73 for taking measurements, e.g. using sensing coils
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

A near field communication (NFC) reader is disclosed. The NFC reader includes an antenna front-end that includes a low pass filter, a matching circuit and an antenna coil. The NFC reader also includes a NFC controller. The NFC controller includes an oscillator coupled to the antenna front-end and the NFC controller is configured to detect a presence of an object in proximity of the antenna front-end using one or more changes in an output of the oscillator. The antenna front-end creates a tank circuit for the oscillator.

Claims

1. A near field communication (NFC) reader, comprising:

an antenna front-end that includes a low pass filter, a matching circuit, and an antenna coil, the antenna front-end having a capacitance and an inductance; and

an NFC controller, wherein the NFC controller includes an oscillator, configured to operate at a boundary of its stability and use the capacitance and the inductance of the antenna front-end as a tank circuit such that the oscillator is resonating at the boundary of its stability based on the capacitance and the inductance of the tank circuit, and coupled to the antenna front-end, and the NFC controller is configured to detect a presence of an object in proximity of the antenna front-end using one or more changes in an output of the oscillator.

2. The NFC reader of claim 1, wherein the one or more changes in the output of the oscillator occur when the presence of the object detunes the antenna front-end.

3. The NFC reader of claim 1, further including:

a transmitter and a receiver.

4. The NFC reader of claim 3, wherein the transmitter and the receiver are configured to be turned on only when the object is detected in the proximity of the antenna front-end.

5. The NFC reader of claim 4, wherein the NFC controller is configured to attempt to communicate with the object using the transmitter and the receiver to determine whether the object is an NFC enabled device.

6. The NFC reader of claim 1, wherein the NFC controller further comprises:

a peak detector configured to measure a peak voltage of the output of the oscillator.

7. The NFC reader of claim 1, wherein the NFC controller further comprises:

a frequency detector configured to measure output frequency of the oscillator.

8. The NFC reader of claim 1, wherein the NFC controller further comprises:

an envelope detector configured to measure an envelope of an output waveform of the oscillator.

9. The NFC reader of claim 1, wherein the NFC controller is configured to detect detuning using one or more of a peak detector, a frequency detector, and an envelope detector coupled to the oscillator.

10. The NFC reader of claim 1, wherein the NFC controller includes Ant1 and Ant2 pins that are configured to be coupled to the antenna coil of the antenna front-end.

11. The NFC reader of claim 10, wherein the NFC controller is configured to measure a voltage difference at the Ant1 and Ant2 pins.

12. The NFC reader of claim 1, wherein the NFC controller includes a control that is configured to cause the oscillator to start resonating using a startup pulse.

13. The NFC reader of claim 1, wherein the oscillator includes a current source and a transistor, and the oscillator is configured to use the capacitance and the inductance of the antenna front-end for the tank circuit.

14. A near field communication (NFC) reader, comprising:

an antenna front-end that includes a low pass filter, a matching circuit, and an antenna coil, the antenna front-end having a capacitance and an inductance; and

an NFC controller, wherein the NFC controller includes an oscillator coupled to the antenna front-end and configured to use the capacitance and the inductance of the antenna front-end as a tank circuit such that the oscillator is resonating at a boundary of its stability based on the capacitance and the inductance of the tank circuit, and the NFC controller is configured to detect a presence of an object in proximity of the antenna front-end using one or more changes in an output of the oscillator, and the NFC controller is configured to determine a width of a startup pulse based on an inductance of the antenna front-end at a time of starting the oscillator.

15. A near field communication (NFC) reader, comprising:

an antenna front-end that includes a low pass filter, a matching circuit, and an antenna coil, the antenna front-end having a capacitance and an inductance; and

an NFC controller, wherein the NFC controller includes an oscillator coupled to the antenna front-end and configured to use the capacitance and the inductance of the antenna front-end as a tank circuit such that the oscillator is resonating at the boundary of its stability based on the capacitance and the inductance of the tank circuit, and the NFC controller is configured to detect a presence of an object in proximity of the antenna front-end using one or more changes in an output of the oscillator, the oscillator is started when the object is not in the proximity of the antenna front-end and a change in inductance of the antenna front-end due to a presence of the object in the proximity detunes the antenna front-end, and the oscillator stops resonating.