RADIOFREQUENCY-WAVE-TRANSPARENT CAPACITIVE SENSOR PAD

• US 20150199042A1
• Filed: 01/10/2014
• Published: 07/16/2015
• Est. Priority Date: 01/10/2014
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Harper, Marc, Mercer, Sean Russell, Standing, William Hadlock, Voth, David
• Granted Patent: US 9,563,316 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: H01Q 1/243 with built-in antennas
• CPC Class Codes: H01Q 1/245 with means for shaping the antenna pattern, e.g. in order to protect user against rf exposure
• CPC Class Codes: H01Q 1/44 using equipment having another main function to serve additionally as an antenna , e.g. means for giving an antenna an aesthetic aspectH01Q1/27 - H01Q1/34 take precedence
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 2017/9455 constructional details of proximity switches using a magnetic detector H03K17/9505
• CPC Class Codes: H03K 2217/94089 Wireless transmission

Abstract

A capacitive sensor pad is co-located with (e.g., overlapping) an RF transmitter without causing significant degradation to the performance of the antenna. In one implementation, tuning the resistance per square in the capacitive sensor pad can provide effective sensor pad range and performance while providing making the capacitive sensor pad sufficiently transparent to radiofrequency waves to provide excellent antenna efficiency, despite the co-location of the capacitive sensor pad and the antenna.

Claims

1. An electronic device comprising:

a capacitive sensor pad configured to detect proximity of a body outside the device; and

a radiofrequency antenna co-located with the capacitive sensor pad and configured to transmit radiofrequency through the capacitive sensor pad.

2. The electronic device of claim 1 further comprising:

a conductive trace extending from the capacitive sensor pad to outside an antenna volume; and

one or more segmenting resistors in the conductive trace configured to move signal resonances within the conductive trace outside of operating bands of the radiofrequency antenna.

3. The electronic device of claim 1 further comprising:

a conductive trace extending from the capacitive sensor pad to outside an antenna volume and overlapping a portion of the radiofrequency antenna; and

one or more segmenting resistors in the conductive trace within the antenna volume configured to move signal resonances within the conductive trace outside of operating bands of the radiofrequency antenna.

4. The electronic device of claim 1 further comprising:

a conductive trace extending from the capacitive sensor pad to outside an antenna volume and overlapping a portion of the radiofrequency antenna; and

a noise-blocking resistor in the conductive trace outside the antenna volume.

5. The electronic device of claim 1 further comprising:

a radiofrequency transmitter coupled to the radiofrequency antenna; and

a transmission power controller coupled to the capacitive sensor pad and the radiofrequency transmitter and configured to adjust transmission power of the radiofrequency transmitter when the capacitive sensor pad exhibits a change in a capacitance.

6. The electronic device of claim 1 further comprising:

a radiofrequency transmitter coupled to the radiofrequency antenna; and

a transmission power controller coupled to the capacitive sensor pad and the radiofrequency transmitter and configured to increase transmission power of the radiofrequency transmitter when the capacitive sensor pad exhibits a change in a capacitance that no longer satisfies a threshold power change condition.

7. The electronic device of claim 1 further comprising:

a radiofrequency transmitter coupled to the radiofrequency antenna; and

a transmission power controller coupled to the capacitive sensor pad and the radiofrequency transmitter and configured to decrease transmission power of the radiofrequency transmitter when the capacitive sensor pad exhibits a change in a capacitance that satisfies a threshold power change condition.

8. The electronic device of claim 1 wherein the capacitive sensor pad has a resistivity above 40,000 ohms/square.

9. The electronic device of claim 1 wherein the capacitive sensor pad has a resistivity substantially within a range of 40,000 ohms/square to 120,000 ohms/square.

10. The electronic device of claim 1 wherein the capacitive sensor pad is directly affixed to the radiofrequency antenna.

11. The electronic device of claim 1 wherein the capacitive sensor pad overlaps and is separated from the radiofrequency antenna by no more than 3 mm.

12. The electronic device of claim 1 wherein the capacitive sensor pad overlaps and is within the areal dimensions of the radiofrequency antenna.

13. A method comprising:

constructing a capacitive sensor pad that is co-located with a radiofrequency antenna, wherein the radiofrequency is positioned to transmit radiofrequency waves through the capacitive sensor pad and the capacitive sensor pad is configured to detect proximity of a conducting body.

14. The method of claim 13 further comprising:

transmitting the radiofrequency waves from the radiofrequency antenna through the capacitive sensor pad.

15. The method of claim 13 further comprising:

detecting a body in the proximity of the capacitive sensor pad.

adjusting transmission power of a radiofrequency transmitter exiting the radiofrequency antenna when the capacitive sensor pad exhibits a change in a capacitance.

16. The method of claim 13 wherein the capacitive sensor pad has a resistivity above 40,000 ohms/square.

17. The method of claim 13 wherein the capacitive sensor pad has a resistivity substantially within a range of 40,000 ohms/square to 120,000 ohms/square.

18. The method of claim 13 wherein the capacitive sensor pad is directly affixed to the radiofrequency antenna.

19. An electronic device comprising:

a sensor pad configured to detect proximity of a body outside the electronic device;

a first surface of a dielectric adjacent to the sensor pad; and

a second surface of a dielectric adjacent to a planar antenna, the planar antenna co-located with the capacitive sensor pad and configured to transmit radiofrequency signals through the capacitive sensor pad.

20. The electronic device of claim 19 wherein the sensor pad is a first sensor pad, the electronic device further comprising:

a second sensor pad placed substantially orthogonally to the first sensor pad.