Method and apparatus for improving the performance of a multi-band antenna in a wireless terminal

• US 20060139211A1
• Filed: 12/29/2004
• Published: 06/29/2006
• Est. Priority Date: 12/29/2004
• Status: Active Grant

• Current Assignee: Sony Ericsson Mobile Communications USA Incorporated (Sony Group Corp.)
• Original Assignee: Sony Ericsson Mobile Communications USA Incorporated (Sony Group Corp.)
• Inventors: Vance, Scott LaDell, Wilcox, Bruce
• Granted Patent: US 7,265,731 B2
• Time in Patent Office: Days
• US Class Current: 343/700.MS
• CPC Class Codes: H01Q 5/328 between a radiating element and ground
• CPC Class Codes: H01Q 5/378 Combination of fed elements with parasitic elements
• CPC Class Codes: H01Q 9/0421 with a shorting wall or a shorting pin at one end of the element H01Q9/0414 takes precedence
• CPC Class Codes: H01Q 9/0442 with particular tuning means

Abstract

A method and apparatus for improving the efficiency of a multi-band antenna in a wireless terminal over a wide range of frequencies is described herein. To compensate for the undesirable coupling that occurs in a low frequency band between a parasitic antenna and a primary antenna in certain designs, a matching network is connected to at least one ground port of the multi-band antenna. The matching network controls the multi-band antenna performance based on the current transmission frequency band. In some embodiments, the matching network is configured to operate as an open circuit when multi-band antenna operates in the low frequency band, and to operate as a short circuit when multi-band antenna operates in the high frequency band.

Claims

1. A multi-band antenna system for a wireless terminal comprising:

a multi-band antenna having a feed port and a ground port;

a transmission circuit connected to the feed port, said transmission circuit configured to provide transmission signals to the multi-band antenna; and

a matching network connected to the ground port, said matching network configured to operate as an open circuit when the multi-band antenna operates in a first frequency band and wherein the matching network is configured to operate as a short circuit when the multi-band antenna operates in a second frequency band.

2. The multi-band antenna system of claim 1 wherein the first frequency band comprises a low frequency band and wherein the second frequency band comprises a high frequency band.

3. The multi-band antenna system of claim 1 wherein the first frequency band comprises a high frequency band and wherein the second frequency band comprises a low frequency band.

4. The multi-band antenna system of claim 1 wherein the matching network comprises a passive circuit configured to operate as an open circuit when the multi-band antenna operates in the first frequency band and to operate as a short circuit when the multi-band antenna operates in the second frequency band.

5. The multi-band antenna system of claim 4 wherein the passive circuit comprises a series inductor-capacitor circuit in parallel with a capacitor or inductor.

6. The multi-band antenna system of claim 5 wherein the passive circuit comprises the series inductor-capacitor circuit in parallel with the inductor when the first frequency band comprises a low frequency band and the second frequency band comprises a high frequency band.

7. The multi-band antenna system of claim 5 wherein the passive circuit comprises the series inductor-capacitor circuit in parallel with the capacitor when the first frequency band comprises a high frequency band and the second frequency band comprises a low frequency band.

8. The multi-band antenna system of claim 1 wherein by controlling the impedance of the multi-band antenna, the matching network implements different antenna types for different transmission frequencies.

9. The multi-band antenna system of claim 8 wherein the first antenna comprises an inverted F-antenna or a planar inverted F-antenna and wherein the second antenna comprises a monopole antenna or bent monopole antenna.

10. The multi-band antenna system of claim 1 wherein the matching network comprises:

a first circuit path;

a second circuit path; and

a switching circuit to selectively connect the ground port to the first circuit path or the to second circuit path based on the current transmission frequency band.

11. The multi-band antenna system of claim 10 wherein the first circuit path comprises an open circuit path and wherein the second circuit path comprises a short circuit path.

12. The multi-band antenna system of claim 11 wherein the switching circuit selectively connects the ground port to the open circuit path when the multi-band antenna operates in a low frequency band and wherein the switching circuit selectively connects the ground port to the short circuit path when the multi-band antenna operates in a high frequency band.

13. The multi-band antenna system of claim 1 further comprising:

a second ground port; and

a second matching network connected to the second ground port, wherein said second matching network is configured to further control the multi-band antenna performance based on the current transmission frequency band.

14. The multi-band antenna system of claim 1 wherein the multi-band antenna comprises:

a primary antenna including the feed port; and

a parasitic antenna capacitively coupled to the primary antenna, said parasitic antenna including a parasitic ground port,

wherein said matching network is connected to the parasitic ground port.

15. A method of improving an efficiency of a multi-band antenna over a wide range of frequencies, the method comprising:

connecting a matching network to a ground port of the multi-band antenna to control an impedance of the multi-band antenna based on a current transmission frequency band, wherein the matching network comprises a matching network configured to operate as an open circuit when the multi-band antenna operates in a first frequency band and to operate as a short circuit when the multi-band antenna operates in a second frequency band.

16. The method of claim 15 wherein the first frequency band comprises a low frequency band and wherein the second frequency band comprises a high frequency band.

17. The method of claim 15 wherein the matching network comprises a first circuit path, a second circuit path, and a switch, wherein connecting the matching network to the ground port comprises selectively controlling the switch to connect the ground port to the first or second circuit paths based on the current transmission frequency band.

18. The method of claim 15 further comprising:

connecting a second matching network to a second ground port of the multi-band antenna; and

configuring the second matching network to further control the impedance of the multi-band antenna based on the current transmission frequency band.

19. The method of claim 15 wherein the multi-band antenna comprises a parasitic antenna capacitively coupled to a primary antenna, wherein connecting the matching network to the ground port comprises connecting the matching network to a parasitic ground port of the parasitic antenna.