Material-discerning proximity sensing

• US 10,474,307 B2
• Filed: 11/30/2015
• Issued: 11/12/2019
• Est. Priority Date: 05/03/2012
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Leek, Alan Henry
• Primary Examiner(s): Shah, Neel D
• Application Number:
  US14/953,554
• Publication Number:
  US 20160077639A1
• Time in Patent Office: 1,443 Days
• Field of Search: 324630, 324658, 345173-178, 343702
• CPC Class Codes: G01D 5/24 by varying capacitance
• CPC Class Codes: G06F 2203/04106 Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/046 by electromagnetic means
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 2217/960705 Safety of capacitive touch and proximity switches, e.g. increasing reliability, fail-safe

Abstract

A material-discerning proximity sensor is arranged to include an antenna that is arranged to radiate a radio-frequency signal. A capacitive sensor is arranged to detect a change in capacitance of the capacitive sensor and to receive the radio-frequency signal. An electrical quantity sensor is arranged to detect a change of the received radio-frequency signal.

Claims

1. A system comprising:

an antenna configured to produce an electromagnetic radio-frequency signal;

a capacitive sensor configured to receive the electromagnetic radio-frequency signal; and

a processor coupled to the antenna and the capacitive sensor, the processor configured to;

detect a change in the electromagnetic radio-frequency signal as received by the capacitive sensor; and

determine whether a valid proximity detection has occurred based on the change in the electromagnetic radio-frequency signal as received by the capacitive sensor.

2. The system of claim 1, wherein the processor is further configured to:

monitor a change in capacitance of the capacitive sensor; and

determine whether the valid proximity detection has occurred further based on the change in the capacitance of the capacitive sensor.

3. The system of claim 1, wherein determining whether the valid proximity detection has occurred is performed in response to a comparison of the change in the electromagnetic radio-frequency signal with a predetermined threshold.

4. The system of claim 1, further comprising a matched network configured to balance transmission characteristics of the antenna and to low pass filter a signal for driving the antenna.

5. The system of claim 1, wherein the processor includes an analog to digital converter, and wherein detecting the change in the electromagnetic radio-frequency signal as received by the capacitive sensor comprises quantifying the change in the electromagnetic radio-frequency signal as received by the capacitive sensor.

6. The system of claim 5, wherein quantifying the change in the electromagnetic radio-frequency signal as received by the capacitive sensor comprises using a sampling rate that is less-than-or-equal-to twice a frequency of a carrier wave of the electromagnetic radio-frequency signal.

7. The system of claim 6, wherein the analog to digital converter is further configured to quantify a change in capacitance of the capacitive sensor.

8. The system of claim 7, wherein the analog to digital converter is further configured to output time-multiplexed readings of the electromagnetic radio-frequency signal as received by the capacitive sensor and of the capacitance of the capacitive sensor.

9. The system of claim 1, wherein the capacitive sensor comprises conductive material having a surface.

10. The system of claim 9, wherein the surface of the conductive material is planar.

11. The system of claim 9, wherein the antenna comprises a coil that, when energized, has an electrical core that extends through a portion of the surface of the conductive material.

12. The system of claim 9, wherein the antenna comprises series of conductive traces on a substrate that surround an inner portion of the capacitive sensor when viewed as a two-dimensional projection using an axis of projection that is not parallel to a portion of the surface of the capacitive sensor.

13. The system of claim 9, wherein the antenna comprises a coil that, when energized, generates an electrical and magnetic field having an upper lobe and a lower lobe, the upper lobe and the lower lobe defining an axis that extends through a portion of the surface of the capacitive sensor.

14. The system of claim 1, further comprising a radio-frequency identification (RFID) signal generator configured to couple an RFID signal to the antenna, wherein the antenna that is configured to radiate a transmitted RFID radio-frequency signal, wherein the capacitive sensor is configured to receive a received RFID radio-frequency signal, wherein the processor includes an analog to digital converter, and wherein the analog to digital converter is configured to output time-multiplexed readings of the electromagnetic radio-frequency signal as received by the capacitive sensor, the received RFID radio-frequency signal, and capacitance of the capacitive sensor.

15. The system of claim 1, wherein the processor is further configured to:

monitor a change in capacitance of the capacitive sensor; and

output a detection signal in response to detecting a proximity of an object and detecting a characteristic of a material of the object.

16. The system of claim 15, wherein the characteristic of the material of the object is a conductivity of the material of the object.

17. A method comprising:

radiating, by an antenna, an electromagnetic radio-frequency signal;

receiving, by a capacitive sensor, the electromagnetic radio-frequency signal;

detecting, by a processor, a change in the electromagnetic radio-frequency signal received by the capacitive sensor;

monitoring, by the processor, the change in the electromagnetic radio-frequency signal received by the capacitive sensor; and

determining, by the processor, whether a valid proximity detection has occurred, based on the change in the electromagnetic radio-frequency signal received by the capacitive sensor.

18. The method of claim 17, further comprising:

monitoring a change in capacitance of the capacitive sensor; and

determining whether the valid proximity detection has occurred further based on the change in the capacitance of the capacitive sensor.

19. The method of claim 18, wherein determining whether the valid proximity detection has occurred is performed in response to a comparison of the change in the electromagnetic radio-frequency signal received by the capacitive sensor with a predetermined threshold.

20. The method of claim 17, wherein the processor includes an analog to digital converter, and wherein detecting the change in the electromagnetic radio-frequency signal received by the capacitive sensor comprises quantifying the change in the electromagnetic radio-frequency signal received by the capacitive sensor using a sampling rate that is less-than-or-equal-to twice a frequency of a carrier wave of the electromagnetic radio-frequency signal.