System and method for reducing SAR values

• US 20030064761A1
• Filed: 09/28/2001
• Published: 04/03/2003
• Est. Priority Date: 09/28/2001
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens Information And Communication Mobile LLC (Siemens AG)
• Inventors: Nevermann, Peter
• Granted Patent: US 7,146,139 B2
• Time in Patent Office: Days
• US Class Current: 455/572
• CPC Class Codes: H04B 1/3838 Arrangements for reducing RF exposure to the user, e.g. by changing the shape of the transceiver while in use
• CPC Class Codes: H04B 2001/0416 having gain or transmission power control
• CPC Class Codes: H04W 52/367 Power values between minimum and maximum limits, e.g. dynamic range

Abstract

A system and method for reducing the Specific Absorption Rate (SAR) of a mobile communication device employs a sensor assembly for sensing when the mobile communication device is in proximity to a body such as a human body, animal body, or the like. The average power of the radio frequency electromagnetic energy radiated by the mobile communication device may then be reduced only when necessary so that the S AR value for the device is maintained below a predetermined acceptable level.

Claims

1. A system for controlling the average power and duration of radio frequency electromagnetic energy radiated by a mobile communication device, comprising:

a sensor assembly for detecting when the mobile communication device is in proximity to a body; and

a controller for controlling radiation of radio frequency electromagnetic energy by the mobile communication device,

wherein the controller is capable of reducing at least one of the average power and the duration of the radio frequency electromagnetic energy radiated by the mobile communication device when the sensor assembly senses that the mobile communication device is in proximity to the body.

2. The system as claimed in claim 1, the mobile communication device being capable of operating in a first mode wherein the mobile communication device is suitable for use in proximity to the body, and a second mode wherein the mobile communication device is unsuitable for use in proximity to the body, wherein, when the sensor assembly senses that the mobile communication device is in proximity to the body, the controller reduces the average power of the radio frequency electromagnetic energy radiated by the mobile communication device when the mobile communication device is in the second mode.

3. The system as claimed in claim 2, wherein the first mode is suitable for voice communication and the second mode is suitable for data communication.

4. The system as claimed in claim 3, wherein the second mode comprises a General Packet Radio Service (GPRS) data transfer mode.

5. The system as claimed in claim 1, the sensor assembly comprising:

a sensor for sensing radio frequency electromagnetic energy within a predetermined frequency band;

an antenna capable of changing its impedance for changing the amount of radio frequency electromagnetic energy reflected when the antenna is in proximity to the body; and

a coupler for directing at least a part of the radio frequency electromagnetic energy reflected by the antenna to the sensor;

wherein the sensor determines proximity of the mobile communication device to the body by measuring radio frequency electromagnetic energy reflected by the antenna in the vicinity of the body.

6. The system as claimed in claim 5, wherein the antenna is detuned when no body is present.

7. The system as claimed in claim 6, wherein the sensor measures the power of the radio frequency electromagnetic energy reflected by the antenna, and wherein the power of the radio frequency electromagnetic energy reflected by the antenna decreases when the mobile communication device is in proximity to the body.

8. The system as claimed in claim 5, wherein the controller determines a reflection coefficient from the radio frequency electromagnetic energy reflected by the antenna, and wherein the determined reflection coefficient deviates from a predetermined reflection coefficient for the antenna in free space when the mobile communication device is in proximity to the body.

9. The system as claimed in claim 8, wherein when the determined reflection coefficient for the antenna is one of greater than a lower threshold reflection coefficient and less than an upper threshold reflection coefficient within a transmit band of the mobile communication device, the mobile communication device is determined to be not in proximity to the body.

10. A system for controlling the average power and duration of radio frequency electromagnetic energy radiated by a mobile communication device, comprising:

means for sensing when the mobile communication device is in proximity to the body; and

means for controlling the average radiation of radio frequency electromagnetic energy by the mobile communication device,

wherein the controlling means is capable of reducing at least one of the power and the duration of the radio frequency electromagnetic energy radiated by the mobile communication device when the mobile communication device is in proximity to the body.

11. The system as claimed in claim 10, the mobile communication device being capable of operating in a first mode wherein the mobile communication device is suitable for use in proximity to the body and a second mode wherein the mobile communication device is unsuitable for use in proximity to the body, wherein, when the sensing means senses that the mobile communication device is in proximity to the body, the controlling means reduces the average radiated power of the mobile communication device when the mobile communication device is in the second mode.

12. The system as claimed in claim 11, wherein the first mode is suitable for voice communication and the second mode is suitable for data communication.

13. The system as claimed in claim 12, wherein the second mode comprises a General Packet Radio Service (GPRS) data transfer mode.

14. The system as claimed in claim 10, the sensing means comprising:

means for sensing radio frequency electromagnetic energy within a predetermined frequency band;

means for receiving radio frequency electromagnetic energy reflected by the antenna; and

means for directing at least a part of the radio frequency electromagnetic energy reflected by the antenna to the sensor;

wherein the proximity of the mobile communication device to the body is determined by measuring radio frequency electromagnetic energy reflected by the antenna.

15. A system for controlling the average power of radio frequency electromagnetic energy radiated by a mobile communication device, the mobile communication device being capable of operating in a first mode wherein the mobile communication device is suitable for use in proximity to a human body and a second mode wherein the mobile communication device is unsuitable for use in proximity to the human body, the system comprising:

a sensor assembly for detecting when the mobile communication device is in proximity to the human body; and

a controller for controlling radiation of radio frequency electromagnetic energy by the mobile communication device,

wherein the controller is capable of reducing the average power of the radio frequency electromagnetic energy radiated by the mobile communication device when the mobile communication device is in the second mode and the sensor assembly senses that the mobile communication device is in proximity to the human body.

16. The system as claimed in claim 15, wherein the first mode is suitable for voice communication and the second mode is suitable for data communication.

17. The system as claimed in claim 16, wherein the second mode comprises a General Packet Radio Service (GPRS) data transfer mode.

18. The system as claimed in claim 15, wherein the controller ascertains a minimum power level for maintaining a communication link such that the power of the radio frequency electromagnetic energy radiated by the mobile communication device is not reduced below the minimum power level.

19. The system as claimed in claim 15, the sensor assembly comprising:

a sensor for sensing radio frequency electromagnetic energy within a predetermined frequency band;

an antenna capable of changing its impedance for changing the amount of radio frequency electromagnetic energy reflected when the antenna is in proximity to the human body

a coupler for directing at least a part of the radio frequency electromagnetic energy reflected by the antenna to the sensor;

wherein the sensor determines proximity of the mobile communication device to the human body by measuring radio frequency electromagnetic energy reflected by the antenna.

20. The system as claimed in claim 19, wherein the antenna is detuned when no human body is present.

21. The system as claimed in claim 20, wherein the sensor measures the power of the radio frequency electromagnetic energy reflected by the antenna, and wherein the power of the radio frequency electromagnetic energy reflected by the antenna decreases when the mobile communication device is in proximity to the human body.

22. The system as claimed in claim 19, wherein the sensor determines a reflection coefficient from the radio frequency electromagnetic energy reflected by the antenna, and wherein the determined reflection coefficient deviates from a predetermined reflection coefficient for the antenna in free space when the mobile communication device is in proximity to the human body.

23. The system as claimed in claim 22, wherein when the determined reflection coefficient for the antenna is one of greater than a lower threshold reflection coefficient and less than an upper threshold reflection coefficient within a transmit band of the mobile communication device, the mobile communication device is determined to be not in proximity to the human body.

24. A method for controlling the SAR value of a mobile communication device, the mobile communication device being capable of operating in a first mode wherein the mobile communication device is suitable for use in proximity to a human body and a second mode wherein the mobile communication device is unsuitable for use in proximity to the human body, the method comprising the steps of:

determining whether the mobile communication device is operating in the first mode or the second mode;

sensing when the mobile communication device is in proximity to the human body; and

reducing the average radiated power of the mobile communication device when the mobile communication device is in the second mode and is in proximity to the human body.

25. The method as claimed in claim 24, further comprising ascertaining a minimum power level for maintaining a communication link such that the power of the radio frequency electromagnetic energy radiated by the mobile communication device is not reduced below the minimum power level.

26. The method as claimed in claim 24, wherein sensing when the mobile communication device is in proximity to a human body comprises:

sampling radio frequency electromagnetic energy reflected by an antenna; and

measuring the reflected radio frequency electromagnetic energy for determining the proximity of the mobile communication device to the human body.

27. The method as claimed in claim 26, wherein the power of the reflected radio frequency electromagnetic energy is measured, the power of the reflected radio frequency electromagnetic energy being decreased when the mobile communication device is in proximity to the human body.

28. The method as claimed in claim 26, further comprising determining a reflection coefficient from the reflected radio frequency electromagnetic energy, wherein the determined reflection coefficient deviates from a predetermined reflection when the mobile communication device is in proximity to the human body.

29. The method as claimed in claim 28, further comprising ascertaining that mobile communication device is not in proximity to the human body when the determined reflection coefficient for the antenna is greater than a lower threshold reflection coefficient and less than an upper threshold reflection coefficient within a transmit band of the mobile communication device.

30. A mobile communication device capable of operating in a first mode wherein the mobile communication device is suitable for use in proximity to a human body and a second mode wherein the mobile communication device is unsuitable for use in proximity to the human body, the mobile communication device comprising:

a sensor assembly for detecting when the mobile communication device is in proximity to the human body; and

a controller for controlling radiation of radio frequency electromagnetic energy by the mobile communication device,

wherein the controller is capable of reducing at least one of the average power and duration of the radio frequency electromagnetic energy radiated by the mobile communication device when the mobile communication device is in the second mode and the sensor assembly senses that the mobile communication device is in proximity to the human body.

31. The mobile communication device as claimed in claim 30, wherein the first mode is suitable for voice communication and the second mode is suitable for data communication.

32. The mobile communication device as claimed in claim 30, wherein the controller ascertains a minimum power level for maintaining a communication link between the mobile communication device and a second communication device, such that the power of the radio frequency electromagnetic energy radiated by the mobile communication device is not reduced below the minimum power level.

33. The mobile communication device as claimed in claim 30, the sensor assembly comprising:

a sensor for sensing radio frequency electromagnetic energy within a predetermined frequency band;

an antenna capable of changing its impedance for changing the amount of radio frequency electromagnetic energy reflected when the antenna is in proximity to the human body; and

a coupler for directing at least a part of the radio frequency electromagnetic energy reflected by the antenna to the sensor;

wherein proximity of the mobile communication device to the human body is determined by measuring radio frequency electromagnetic energy reflected by the antenna.

34. The mobile communication device as claimed in claim 33, wherein the antenna is detuned when no human body is present.

35. The mobile communication device as claimed in claim 34, wherein the sensor measures the power of the radio frequency electromagnetic energy reflected by the antenna, the power of the radio frequency electromagnetic energy reflected by the antenna being decreased when the mobile communication device is in proximity to the human body.

36. The mobile communication device as claimed in claim 33, wherein the controller determines a reflection coefficient from the radio frequency electromagnetic energy reflected by the antenna, and wherein the determined reflection coefficient deviates from a predetermined reflection coefficient for the antenna in free space when the mobile communication device is in proximity to the human body.

37. The mobile communication device as claimed in claim 36, wherein when the determined reflection coefficient for the antenna is one of greater than a lower threshold reflection coefficient and less than an upper threshold reflection coefficient within a transmit band of the mobile communication device, the mobile communication device is determined to be not in proximity to the human body.