MATERIAL-DISCERNING PROXIMITY SENSING

• US 20130293244A1
• Filed: 06/26/2012
• Published: 11/07/2013
• Est. Priority Date: 05/03/2012
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Leek, Alan Henry
• Granted Patent: US 9,201,548 B2
• Time in Patent Office: Days
• US Class Current: 324/630
• 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 material-discerning proximity sensing device, comprising

an antenna that is arranged to radiate a radio-frequency signal;

a capacitive sensor that is arranged to detect a change in capacitance of the capacitive sensor and that is arranged to receive the radio-frequency signal; and

an electrical quantity sensor that is arranged to detect a change of the received radio-frequency signal.

2. The device of claim 1, further comprising a matched network that is arranged to balance transmission characteristics of the antenna and to low pass filter a signal used to drive the antenna.

3. The device of claim 1, wherein the electrical quantity sensor comprises an analog to digital converter is arranged to quantify the detected change of the received radio-frequency signal.

4. The device of claim 1, wherein the electrical quantity sensor comprises an analog to digital converter is arranged to quantify the detected change of the received radio-frequency signal using a sampling rate that is less-than-or-equal-to at least twice the frequency of a carrier wave of the transmitted radio-frequency signal.

5. The device of claim 4, wherein the analog to digital converter is arranged to quantify the detected change of the capacitance of the capacitive sensor.

6. The device of claim 5, wherein the analog to digital converter is arranged to output time-multiplexed readings of the received radio-frequency signal and the capacitance of the capacitive sensor.

7. The device of claim 1, wherein the capacitive sensor is conductive material arranged having a surface.

8. The device of claim 7, wherein the surface of the capacitive sensor is planar.

9. The device of claim 7, wherein the antenna is arranged as a coil that, when energized, has an electrical core that extends through a portion of the surface of the capacitive sensor.

10. The device of claim 7, wherein the antenna is arranged as arranged as 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.

11. The device of claim 7, wherein the antenna is arranged as a coil that, when energized, generates an electrical and magnetic field having an upper lobe and a lower lobe, the upper lobe and lower lobe defining an axis that extends through a portion of the surface of the capacitive sensor.

12. The device of claim 11, an antenna that is arranged to radiate a radio-frequency signal using a transmit output power below the FCC threshold requiring certification.

13. The device of claim 12, comprising an RFID (radio-frequency identification) signal generator that is arranged to couple an RFID signal to the antenna, wherein the antenna that is arranged to radiate an RFID radio-frequency signal, wherein the capacitive sensor is arranged to receive the RFID radio-frequency signal, and wherein the analog to digital converter is arranged to output time-multiplexed readings of the received radio-frequency signal, the received RFID radio-frequency signal, and the capacitance of the capacitive sensor.

14. A material-discerning proximity sensing system, comprising:

an antenna that is arranged to radiate a radio-frequency signal;

a capacitive sensor that is arranged to detect a change in capacitance of the capacitive sensor and that is arranged to receive the radio-frequency signal;

a electrical quantity sensor that is arranged to detect a change of the received radio-frequency signal; and

a processor that is arranged to monitor detected changes of the received radio-frequency signal and in response to the detected changes of the received radio-frequency signal determine whether a valid proximity detection has occurred.

15. The system of claim 14, wherein the processor is arranged to monitor detected changes in capacitance of the capacitive sensor, and in response to the detected changes in capacitance of a capacitive sensor and the detected changes of the received radio-frequency signal determine whether a valid proximity detection has occurred.

16. The system of claim 14, wherein the determination whether a valid proximity detection has occurred is made in response to a comparison of the detected changes with a predetermined threshold.

17. A method for material-discerning proximity sensing, comprising:

radiating a radio-frequency signal using an antenna;

detecting a change in capacitance of a capacitive sensor;

receiving the radio-frequency signal using the capacitive sensor;

detecting a change of the received radio-frequency signal;

monitoring the detected changes of the received radio-frequency signal; and

determining whether a valid proximity detection has occurred in response to the detected changes of the received radio-frequency signal.

18. The method of claim 17, comprising:

monitoring detected changes in capacitance of the capacitive sensor; and

determining whether a valid proximity detection has occurred in response to the detected changes in capacitance of the capacitive sensor and the detected changes of the received radio-frequency signal.

19. The method of claim 18, wherein the determination whether a valid proximity detection has occurred is made in response to a comparison of the detected changes with a predetermined threshold.

20. The method of claim 17, comprising using an analog to digital converter to quantify detected changes of the received radio-frequency signal using a sampling rate that is less-than-or-equal-to at least twice the frequency of a carrier wave of the transmitted radio-frequency signal.