ELECTRONIC DEVICE WITH ISOLATED ANTENNAS

• US 20100156741A1
• Filed: 12/19/2008
• Published: 06/24/2010
• Est. Priority Date: 12/19/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Xu, Hao, Chiang, Bing, Vazquez, Enrique Ayala
• Granted Patent: US 8,866,692 B2
• Time in Patent Office: Days
• US Class Current: 343/846
• CPC Class Codes: H01Q 1/2291 used in bluetooth or WI-FI devices of Wireless Local Area Networks [WLAN] H01Q1/241 takes precedence; WLAN in general H04W
• CPC Class Codes: H01Q 1/48 Earthing means; Earth screens; Counterpoises
• CPC Class Codes: H01Q 1/521 reducing the coupling between adjacent antennas

Abstract

Antennas for electronic devices are provided. First and second antennas may be mounted within an electronic device. Free-space coupling between the first and second antennas may give rise to interference. The first and second antennas may be coupled to a global ground. The global ground may be formed using a conductive member in the electronic device such as a conductive frame member. Signals that pass between the antennas through the global ground may serve as canceling signals that reduce the magnitude of free-space interference signals and thereby improve antenna isolation. The antennas may be coupled to the global ground using electrical paths or through near-field electromagnetic coupling. Coupling efficiency to the global ground may be enhanced by configuring the conductive traces of one or both of the antennas to form a resonant circuit.

Claims

1. An electronic device, comprising:

a first antenna having a first antenna resonating element and a first antenna local ground;

a second antenna having a second antenna resonating element and a second antenna local ground, wherein antenna interference results when a first version of a transmitted antenna signal from the first antenna is received by the second antenna through a free-space path; and

a global ground structure that is coupled to the first antenna and that is coupled to the second antenna, wherein a second version of the transmitted antenna signal from the first antenna is received at the second antenna through the global ground structure and reduces the antenna interference.

2. The electronic device defined in claim 1 wherein the global ground structure comprises a metal frame member for the electronic device.

3. The electronic device defined in claim 1 wherein the first antenna comprises a first planar substrate and wherein the second antenna comprises a second planar substrate and wherein the first and second planar substrates do not lie in a common plane.

4. The electronic device defined in claim 1 wherein the first antenna comprises conductive traces that are configured to form a resonant circuit.

5. The electronic device defined in claim 1 wherein the first antenna local ground comprises a conductive trace having two ends spaced apart by a gap to form a series capacitance for a resonant circuit.

6. The electronic device defined in claim 1 wherein the first antenna local ground comprises a conductive trace having two ends spaced apart by a gap to form a series capacitance for a resonant circuit.

7. The electronic device defined in claim 6 wherein the first antenna local ground comprises a C-shaped conductive trace.

8. The electronic device defined in claim 1 wherein the first antenna local ground comprises a C-shaped conductive trace.

9. The electronic device defined in claim 1 wherein the first antenna comprises conductive traces that are configured to electromagnetically couple to the global ground structure.

10. The electronic device defined in claim 9 further comprising a conductive path between the second antenna and the global ground structure.

11. The electronic device defined in claim 1 further comprising a conductive path between the second antenna and the global ground structure.

12. The electronic device defined in claim 1 wherein the first antenna is a single band antenna that is configured to operate at 5 GHz and the second antenna is a dual band antenna that is configured to operate at 2.4 GHz and 5 GHz.

13. An antenna system, comprising:

a global ground structure formed at least partly from a metal structural member in an electronic device;

a first antenna that is coupled to the global ground structure; and

a second antenna that is coupled to the global ground structure, wherein signals that pass between the first and second antennas through the global ground structure at least partially cancel interference signals that pass between the first and second antennas over a free-space path and increase isolation between the first and second antennas.

14. The antenna system defined in claim 13 wherein the first antenna comprises a local ground trace having a portion that is parallel to the metal structural member.

15. The antenna system defined in claim 13 wherein the first antenna comprises conductive structures that form a resonant circuit.

16. The antenna system defined in claim 15 wherein the conductive structures that form the resonant circuit comprise a C-shaped local ground trace for the first antenna.

17. An electronic device, comprising:

storage and processing circuitry;

radio-frequency transceiver circuitry coupled to the storage and processing circuitry;

a metal member;

a first antenna; and

a second antenna, wherein the first antenna is electromagnetically coupled to the metal member so that signals pass between the first and second antennas through the metal member and at least partially cancel interference signals that pass between the first and second antennas over a free-space path to increase isolation between the first and second antennas.

18. The electronic device defined in claim 17 wherein the metal member comprises a planar metal frame for the electronic device, the electronic device further comprising a first transmission line that is coupled between the radio-frequency transceiver circuitry and the first antenna and a second transmission line that is coupled between the radio-frequency transceiver circuitry and the second antenna, wherein the first transmission line has a first conductor connected to a first trace in the first antenna, and wherein the first transmission line has a second conductor connected to a ground trace in the first antenna.

19. The electronic device defined in claim 18 wherein the ground trace comprises portions forming a loop that creates an inductance and a gap that creates a capacitance in series with the inductance.

20. The electronic device defined in claim 19 wherein the first and second antennas comprise planar substrates that do not lie in a common plane, wherein the electronic device is a wireless base station, and wherein the storage and processing circuitry comprises at least one disk drive for the wireless base station.