System and method for adaptive beamforming for specific absorption rate control

• US 8,442,457 B2
• Filed: 09/07/2010
• Issued: 05/14/2013
• Est. Priority Date: 09/08/2009
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Harel, Haim, Chen, Phil F., Kludt, Kenneth
• Primary Examiner(s): VO, NGUYEN THANH
• Application Number:
  US12/876,977
• Publication Number:
  US 20110059706A1
• Time in Patent Office: 980 Days
• Field of Search: 455/575.7, 455/101, 455/115.1, 455/115.3, 455/117, 455/129
• US Class Current: 455/101
• CPC Class Codes: H01Q 3/00 Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system means for positioning H01Q1/125
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
• 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 17/103 Reflected power, e.g. return loss
• CPC Class Codes: H04B 7/0404 the mobile station comprising multiple antennas, e.g. to provide uplink diversity
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0689 using different transmission schemes, at least one of them being a diversity transmission scheme
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A system may include a modifiable mobile device having at least two antennas coupled to fractional amplifiers, with returned power detectors. A beamformer unit provides adaptive beam shaping pattern, and a baseband processor provides beam pattern requirements, wherein the beamformer unit modifies the beam pattern requirements with return loss sampling information to shape the adaptive beam pattern so that a transmitted beam pattern minimizes transmitted power reflected back to the mobile device. A method may include regularly measuring a return power level, if output power is greater than a specific absorption rate level, comparing the return power level to a first threshold, else implementing mobile transmit diversity (MTD), and repeating. If the return power level is greater than the first threshold, implementing a MTD combined with reflection-based beamforming that modifies beam pattern requirements of the mobile device with return loss sampling information to create an adaptive beam pattern.

Claims

1. A method comprising the steps of:

a) measuring a return power level present at antennas of a modifiable mobile communication device at regular time intervals;

b) if an output power of the modifiable mobile communication device is greater than a predefined specific absorption rate level, comparing the return power level to a first threshold and skip to step e);

c) if an output power of the modifiable mobile communication device is less than or equal to a predefined specific absorption rate level, implementing mobile transmit diversity; and

d) repeating steps a-c;

e) if the return power level is greater than the first threshold, implementing a mobile transmit diversity algorithm combined with a reflection-based beamforming technique, the reflection-based beamforming technique providing an adaptive beam shaping pattern that shapes a transmitted beam pattern to minimize an amount of reflected transmitted power;

f) re-measuring the return power level;

g) if the return power level has increased, applying a change to a diversity parameter of the mobile transmit diversity algorithm based on the results of the evaluating step;

h) if the return power level is less than a second threshold, repeating steps a-c; and

i) if the return power level is equal to or greater than the second threshold, repeating steps e-g.

2. The method of claim 1, further including the step of obtaining the first threshold from a lookup table.

3. The method of claim 1, further including the step of calculating the first threshold.

4. The method of claim 3, wherein the first threshold equals a loaded return loss minus an unloaded return loss plus a margin.

5. The method of claim 1, wherein the reflection-based beamforming technique includes the step of modifying a beam pattern requirement of the modifiable communication device with return loss sampling information to create the adaptive beam shaping pattern.

6. The method of claim 1, further including the step of skipping phase diversity parameters in a gradient-seeking mobile transmit diversity algorithm that result in return loss increases.

7. The method of claim 6, wherein if a phase continuity constraint is mandated for the modifiable mobile communication device, a resolution in the changes to the phase diversity parameter can be minimized by further including the step of reducing transmitted power by an amount of power exceeding specific absorption rate levels at a current frequency and diversity value.

8. A method comprising the steps of;

a) measuring a return power level present at antennas of a modifiable mobile communication device at regular time intervals;

b) if an output power of the modifiable mobile communication device is greater than a predefined specific absorption rate level, comparing the return power level to a first threshold and skip to step e);

c) if an output power of the modifiable mobile communication device is less than or equal to a predefined specific absorption rate level, implementing mobile transmit diversity; and

d) repeating steps a-c;

e) if the return power level is greater than the first threshold, implementing a mobile transmit diversity algorithm combined with reflection-based beamforming, the reflection-based beamforming providing an adaptive beam shaping pattern that shapes a transmitted beam pattern to minimize an amount of reflected transmitted power;

f) re-measuring the return power level;

g) if the return power level has increased, reducing the output power of the modifiable mobile communication device;

h) if the return power level is less than a second threshold, repeating steps a-c; and

i) if the return power level is equal to or greater than the second threshold, repeating steps e-g.

9. The method of claim 8, further including the step of obtaining the first threshold from a lookup table.

10. The method of claim 8, further including the step of calculating the first threshold.

11. The method of claim 10, wherein the first threshold equals a loaded return loss minus an unloaded return loss plus a margin.

12. The method of claim 8, wherein the reflection-based beamforming includes the step of modifying a beam pattern requirement of the modifiable communication device with return loss sampling information to create the adaptive beam shaping pattern.