Proximity sensor and antenna system arrangement for metal housing

• US 9,490,885 B1
• Filed: 05/01/2015
• Issued: 11/08/2016
• Est. Priority Date: 05/01/2015
• Status: Expired due to Fees

• Current Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Original Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Inventors: Zheng, Ming, Napoles, Adrian
• Primary Examiner(s): Mitchell, Nathan
• Application Number:
  US14/702,197
• Time in Patent Office: 557 Days
• US Class Current: 1/1
• CPC Class Codes: H04B 7/0608 Antenna selection according to transmission parameters
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

A unified proximity sensor including multiple physically separated radio antenna structure for mobile electronic devices that senses proximity of a person to the antennae. Changes in capacitances of the antennae are detected based on a low frequency signal output by a single capacitance sensor. As a human body approaches any of the antennae, this capacitance increases. Based on the increase in capacitance, the transmission powers of radio signals emitted by the antennae are reduced.

Claims

1. A device, comprising:

a first antenna;

a second antenna, physically separate and electrically insulated from the first antenna;

a first radio frequency (RF) transmitter electrically coupled to the first antenna via a first RF feed and configured to transmit a first RF signal at a first frequency;

a second radio frequency (RF) transmitter electrically coupled to the second antenna via a second RF feed and configured to transmit a second RF signal at a second frequency;

a capacitance sensor configured to determine a capacitance attached to an electrode of the capacitance sensor using a sensing signal output by the capacitance sensor via the electrode, the sensing signal having a lower frequency than the first RF signal and the second RF signal, the capacitance sensor to determine a capacitance value that is proportional to the capacitance;

a first inductor electrically connecting the first antenna to the electrode of the capacitance sensor, the first inductor being configured to (i) pass the sensing signal between the electrode and the first antenna, and (ii) block transmission of the first RF signal from the first antenna into the capacitance sensor;

a second inductor electrically connecting the first antenna to the second antenna, the second inductor being configured to (i) pass the sensing signal between the first antenna and the second antenna, (ii) block transmission of the first RF signal from the first antenna to the second antenna, and (iii) block transmission of the second RF signal from the second antenna to the first antenna;

a first capacitor arranged between the first RF transmitter and the first antenna, the first capacitor to (i) pass the first RF signal from the first RF transmitter to the first antenna, and (ii) block transmission of the sensing signal into the first RF transmitter;

a second capacitor arranged between the second RF transmitter and the second antenna, the second capacitor to (i) pass the second RF signal from the second RF transmitter to the second antenna, and (ii) block transmission of the sensing signal into the first RF transmitter; and

a digital comparator,

wherein;

the digital comparator determines that the capacitance value is greater than a threshold value, and

the first RF transmitter reduces a first transmission power of the first RF signal, and the second RF transmitter to reduce a second transmission power of the second RF signal, in response to the capacitance value being greater than the threshold value, and

wherein the capacitance value increases as a human body approaches either the first or second antennae.

2. The device of claim 1, further comprising:

a metal housing proximate to the first antenna and to the second antenna;

a first electrical insulator arranged between the metal housing and the first antenna; and

a second electrical insulator arranged between the metal housing and the second antenna.

3. The device of claim 1, further comprising:

a first impedance matching circuit arranged between the first RF transmitter and the first capacitor; and

a second impedance matching circuit arranged between the second RF transmitter and the second capacitor.

4. A device comprising:

a capacitance sensor configured to output a sensing signal via an electrode to determine a capacitance, and to output a digital value based on the capacitance;

a first antenna;

a first feed electrically connected to the first antenna, the first feed configured to receive a first signal having a first frequency that is greater than a frequency of the sensing signal, the first antenna to transmit the first signal;

a first capacitor included in the first feed, the first capacitor configured to (i) pass the first signal to first antenna, and (ii) block passage of the sensing signal;

a second antenna;

a second feed electrically connected to the second antenna, the second feed configured to receive a second signal having a second frequency that is greater than the frequency of the sensing signal, the second antenna to transmit the second signal;

a second capacitor included in the second feed, the second capacitor configured to (i) pass the second signal to second antenna, and (ii) block passage of the sensing signal;

a first inductor electrically connecting the electrode of the capacitance sensor to the first antenna, the first inductor configured to (i) pass the sensing signal between the electrode and the first antenna, and (ii) block passage of the first signal; and

a second inductor electrically connecting the first antenna to the second antenna, the second inductor configured to (i) pass the sensing signal between the first antenna and the second antenna, and (ii) block passage of the first signal and the second signal.

5. The device of claim 4, further comprising:

a first transmitter connected to the first feed and configured to output the first signal; and

a first digital comparator that compares the digital value based on the capacitance with a first threshold value,

wherein the first transmitter reduces a transmission power of the first signal from a first power level to a second power level in response to the digital value exceeding the first threshold value.

6. The device of claim 5, wherein the first transmitter increases the transmission power from the second power level to the first power level in response to the digital value falling below the first threshold value.

7. The device of claim 5, further comprising:

a second digital comparator that compares the digital value based on the capacitance with a second threshold value, the second threshold value being smaller than the first threshold value,

wherein the first transmitter increases the transmission power from the second power level to the first power level in response to the digital value below the second threshold value.

8. The device of claim 5, wherein a first value of the digital value when the capacitance consists only of an intrinsic capacitance is no more than five hundred times a sum of the first value and the first threshold value, so as to reliably detect a human body at a threshold distance from either of the first or second antennae.

9. The device of claim 4, further comprising:

a first transmitter electrically connected to the first feed and configured to output the first signal; and

a processor communicatively coupled to the first transmitter;

a memory including instruction operable to be executed by the processor to perform a set of actions to configure the processor to;

receive the digital value from the capacitance sensor;

instruct the first transmitter to reduce transmission power of the first signal in proportion to an increase in a value of the digital value.

10. The device of claim 4, further comprising:

a third feed electrically connected to the first antenna, the third feed configured to receive a third signal having a frequency that is higher than the frequency of the sensing signal and lower than the first frequency, the first antenna to transmit the third signal;

a third capacitor included in the third feed, the third capacitor configured to (i) pass the third signal to the first antenna and (ii) block passage of the sensing signal; and

a third inductor included in the third feed, the third inductor configured to (i) pass the third signal and (ii) block passage of the first signal.

11. The device of claim 10, wherein the first feed and the third feed electrically connect to the first antenna via a shared conductor.

12. The device of claim 4, further comprising:

a metal housing proximate to the first antenna and to the second antenna;

a first electrical insulator arranged between the metal housing and the first antenna; and

a second electrical insulator arranged between the metal housing and the second antenna.

13. A device comprising:

a first feed port configured to receive a first signal;

a first antenna;

a second feed port configured to receive a second signal;

a second antenna that is physically separate from the first antenna;

a capacitance sensor configured to determine a capacitance coupled to an electrode using a third signal output via the electrode;

first means for blocking passage of the third signal and passing the first signal, the first means arranged between the first feed port and the first antenna;

second means for blocking passage of the third signal and passing the second signal, the second means arranged between the second feed port and the second antenna;

third means for blocking passage of the first signal and passing the third signal, the third means arranged between the electrode of the capacitance sensor and the first antenna;

fourth means for blocking passage of the first signal and passing the third signal, the fourth means arranged between the first antenna to the second antenna; and

fifth means for blocking passage of the second signal and passing the third signal, the fifth means arranged between the first antenna to the second antenna.

14. The device of claim 13, wherein the capacitance sensor further comprises a digital output from which the capacitance sensor outputs a value based on the capacitance coupled to the electrode, the device further comprising:

a first transmitter electrically connected to first feed port, the first transmitter configured to transmit the first signal; and

means for comparing the value from the digital output with a threshold value,

wherein the first transmitter reduces a transmission power of the first signal in response to the value from the digital output exceeding the threshold value.

15. The device of claim 13, wherein at least one of the first means for blocking, the second means for blocking, the third means for blocking, the fourth means for blocking, and the fifth means for blocking comprises a resonant circuit.

16. The device of claim 13, wherein at least one of the first means for blocking, the second means for blocking, the third means, and a combination of the fourth and fifth means for blocking comprises a semiconductor switch.

17. The device of claim 16, further comprising:

a first transceiver configured to communicate at the first frequency, electrically connected to first feed;

a second transceiver configured to communicate at the second frequency, electrically connected to the second feed; and

a switch controller configured to control the semiconductor switch based on whether either of the first transceiver and the second transceiver is scheduled to communicate.

18. The device of claim 13, wherein at least one of the third means for blocking and a combination of the fourth and third fifth for blocking comprises an inductor.

19. The device of claim 13, wherein at least one of the first means for blocking and the second means for blocking comprises a capacitor.

20. The device of claim 13, further comprising:

a metal housing proximate to the first antenna and to the second antenna;

a first electrical insulator arranged between the metal housing and the first antenna; and

a second electrical insulator arranged between the metal housing and the second antenna.