CONTROLLING MTD ANTENNA VSWR AND COUPLING FOR SAR CONTROL

• US 20140125546A1
• Filed: 06/21/2012
• Published: 05/08/2014
• Est. Priority Date: 06/21/2011
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Harel, Haim, Kludt, Kenneth, Chen, Phil
• Granted Patent: US 9,525,203 B2
• Time in Patent Office: Days
• US Class Current: 343/860
• CPC Class Codes: H01Q 1/50 Structural association of antennas with earthing switches, lead-in devices or lightning protectors
• CPC Class Codes: H03H 7/40 Automatic matching of load impedance to source impedance
• CPC Class Codes: H04B 1/0458 Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages matching circuits in general H03H
• 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

Abstract

A method and apparatus has been developed to reduce SAR for a mobile device by designing appropriate matching circuits between each antenna and its power amplifier. In the presence of such matching circuits the normal phase adjustments may be carried out to provide a preferred safe SAR level that can be maintained during phase adjustment without sacrificing TRP.

Claims

1. A mobile transmit diversity device comprising

a plurality of antennas within each others near field, each antenna receiving a signal from a respective power amplifier mediated by a matching circuit, said matching circuits having

a network topology comprising a plurality of impedance components wherein the values of impedance are chosen to produce reflection coefficients and VSWR values that reduce TRP at a phase setting that produces the worst case SAR by the coupled signals among the antennas.

2. The mobile transmit diversity device of claim 1, where the network topology is an L topology and the impedance components are either inductive or capacitive components.

3. A mobile transmit diversity device being subject to a SAR limit comprising

a plurality of antennas, each antenna receiving a signal from a respective power amplifier mediated by a matching circuit, said matching circuits having

a network topology comprising a plurality of impedance components wherein the values of impedance are chosen to produce reflection coefficients and VSWR values that produces constant average TRP without exceeding the SAR limit.

4. The mobile transmit diversity device of claim 3 where the network topology is an L topology and the impedance components are either inductive or capacitive components.

5. A mobile transmit diversity unit being subject to a SAR limit comprising

a plurality of antennas, each antenna receiving a signal from a respective power amplifier mediated by a matching circuit, said matching circuits having

a network topology chosen to produce high antenna coupling as measured by VSWR values and that produces higher average TRP without exceeding the SAR limit.

6. The mobile transmit diversity unit of claim 5, wherein the network topology is an L topology and the impedance components are either inductive or capacitive components.

7. A mobile transmit diversity unit comprising

a plurality of antennas within each others near field, each antenna receiving a signal from a respective power amplifier mediated by a matching circuit, said matching circuits chosen to minimize a worst case SAR value.

8. The mobile transmit diversity unit of claim 7, wherein the network topology is an L topology and the impedance components are either inductive or capacitive components.

9. A method for selecting matching circuits in a mobile transmit diversity device having a plurality of antennas, each antenna receiving a signal from a respective power amplifier mediated by a matching circuit, comprising

determining the point at which the SAR achieves its highest value, and if that highest value exceeds a preset SAR threshold then

sending an interference maximum of the antenna radiation pattern to that point by selecting a phase difference between the antennas and

adjusting the matching circuits to reduce TRP so that SAR is below a preset SAR threshold.

10. The method of claim 9, wherein the matching circuits are adjusted by selecting the impedance value of components.