Multi-band transmit antenna

• US 9,673,872 B2
• Filed: 07/13/2012
• Issued: 06/06/2017
• Est. Priority Date: 11/15/2011
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Low, Zhen Ning, Kasturi, Sreenivas
• Primary Examiner(s): Barnie, Rexford
• Assistant Examiner(s): Mourad, Rasem
• Application Number:
  US13/549,314
• Publication Number:
  US 20130119924A1
• Time in Patent Office: 1,789 Days
• Field of Search: 307104
• CPC Class Codes: H04B 5/263 Multiple coils at either side
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

This disclosure provides systems, methods and apparatus for tuning a transmit antenna for operation in a plurality of frequency bands. In one aspect, a transmitting antenna system is provided. The transmitting antenna system includes an active transmit antenna and a tunable passive antenna. The active antenna is configured to transmit a field over a plurality of operating frequencies. The passive antenna is configured to transmit a field over at least two frequencies of the plurality of operating frequencies. In one aspect, the tunable passive antenna includes a network of a plurality of reactive elements. In another aspect, the plurality of operating frequencies is selected from a set including a charging frequency, an NFC frequency, and a communication frequency.

Claims

1. An apparatus for wireless charging comprising a transmitting antenna comprising:

an active antenna circuit configured to generate a first wireless field; and

a passive antenna circuit including a parasitic element and at least one capacitor and at least one inductor that are connected to the parasitic element, the passive antenna circuit configured to generate a second wireless field, the passive antenna circuit having a first reactance at a first operating frequency and a second reactance at a second operating frequency, the at least one capacitor and the at least one inductor configured to tune the passive antenna circuit to generate the second wireless field at the first and second operating frequencies, a combination of the first wireless field and the second wireless field creates a combined wireless field having a field strength that does not deviate beyond 60% across a first axis of the active antenna in a charging area.

2. The apparatus of claim 1, wherein said passive antenna circuit comprises a network of a plurality of reactive elements.

3. The apparatus of claim 1, wherein the first operating frequency is one of at least two frequencies of a plurality of operating frequencies and the second operating frequency is not one of the at least two frequencies of the plurality of operating frequencies.

4. The apparatus of claim 1, wherein the at least one capacitor is chosen with a fixed, non-switchable capacitance and the at least one inductor is chosen with a fixed, non-switchable inductance, and wherein the first frequency determines the first reactance and the second frequency determines the second reactance.

5. The apparatus of claim 1, wherein the second reactance comprises an effectively infinite reactance.

6. The apparatus of claim 1, wherein the second reactance comprises an effectively zero reactance.

7. The apparatus of claim 1, wherein the first operating frequency is about 6.78 MHz.

8. The apparatus of claim 1, wherein the second operating frequency is around 13.56 MHz.

9. The apparatus of claim 1, wherein the second operating frequency is around 40.68 MHz.

10. A method of charging a wireless device, the method comprising:

generating, at an active antenna circuit, a first wireless field at a first operating frequency;

generating, at a passive antenna circuit including a parasitic element and at least one capacitor and at least one inductor that are connected to the parasitic element, a second wireless field at the first operating frequency; and

generating, at the passive antenna circuit, the second wireless field at a second operating frequency,

the passive antenna circuit having a first reactance at the first operating frequency and a second reactance at the second operating frequency, the at least one capacitor and the at least one inductor configured to tune the passive antenna circuit to generate the second wireless field at the first and second operating frequencies, a combination of the first wireless field and the second wireless field creates a combined wireless field having a field strength that does not deviate beyond 60% across a first axis of the active antenna circuit in a charging area.

11. The method of claim 10, wherein said passive antenna circuit comprises a network of a plurality of reactive elements.

12. The method of claim 10, wherein the second reactance comprises an effectively infinite reactance.

13. The method of claim 10, wherein the second reactance comprises an effectively zero reactance.

14. The method of claim 10, wherein the first operating frequency is about 6.78 MHz.

15. The method of claim 10, wherein the second operating frequency is around 13.56 MHz.

16. The method of claim 10, wherein the second operating frequency is around 40.68 MHz.

17. An apparatus for charging a wireless device, the apparatus comprising:

means for actively generating a first wireless field at a first operating frequency; and

means for passively generating a second wireless field at the first operating frequency and at a second operating frequency, the means for passively generating comprising means for providing a first reactance at the first operating frequency and a second reactance at the second operating frequency; and

means for tuning the means for passively generating the second wireless field at the first and second operating frequencies, a combination of the first wireless field and the second wireless field creates a combined wireless field having a field strength that does not deviate beyond 60% across a first axis of the means for actively generating in a charging area.

18. The apparatus of claim 17, wherein said means for passively generating comprises means for providing reactance.

19. A non-transitory computer-readable medium comprising code that, when executed, causes an apparatus to:

generate, at an active antenna circuit, a first wireless field at a first operating frequency;

generate, at a passive antenna circuit including a parasitic element and at least one capacitor and at least one inductor that are connected to the parasitic element, a second wireless field at the first operating frequency; and

generate, at the passive antenna circuit, the second wireless field at a second operating frequency,

the passive antenna circuit having a first reactance at the first operating frequency and a second reactance at the second operating frequency, the at least one capacitor and the at least one inductor configured to tune the passive antenna circuit to generate the second wireless field at the first and second operating frequencies, a combination of the first wireless field and the second wireless field creates a combined wireless field having a field strength that does not deviate beyond 60% across a first axis of the active antenna circuit in a charging area.