Antenna Matching for MIMO Transceivers

• US 20100248651A1
• Filed: 03/27/2009
• Published: 09/30/2010
• Est. Priority Date: 03/27/2009
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Dent, Paul Wilkinson
• Granted Patent: US 8,055,216 B2
• Time in Patent Office: Days
• US Class Current: 455/78
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• CPC Class Codes: H01Q 21/28 Combinations of substantially independent non-interacting antenna units or systems multiple beam H01Q25/00
• CPC Class Codes: H04B 17/14 of the whole transmission and reception path, e.g. self-test loop-back
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity

Abstract

A multiple antenna system is described herein that mitigates the negative effects of mutually coupled antennas on the connected transmitters and/or receivers. The antenna system comprises a directional coupler and two or more antennas. The directional coupler comprises multiple communication ports that each connect to corresponding antenna ports. The connection ports each connect to a different transmitter, receiver, or transceiver. A transmission line connects each antenna port to an antenna. The lengths of the transmission lines and the coupling factor of the directional coupler are selected to decouple the communication ports of the directional coupler. More particularly, the coupling factor and the transmission line lengths are selected so that antenna crosstalk signals caused by mutual coupling between the antennas and the coupled signals produced by the directional coupler have the same magnitude but opposite phase at the communication ports of the directional coupler.

Claims

1. An antenna system for a communication terminal comprising:

a directional coupler comprising multiple communication ports that each connect to a respective antenna port;

a plurality of antennas; and

a plurality of transmission lines, each connecting the antenna ports of the directional coupler to respective antennas, wherein the lengths of the transmission lines are selected so that antenna crosstalk signals caused by mutual coupling between the antennas and coupled signals produced by the directional coupler have opposite phase at the communication ports of the directional coupler.

2. The antenna system of claim 1 further comprising a plurality of transmitters, each connected to a different communication port of the directional coupler.

3. The antenna system of claim 2 wherein the selected transmission line lengths further enable the antenna crosstalk signals and transmission signals to be in phase at the antenna ports of the directional coupler.

4. The antenna system of claim 1 wherein the directional coupler comprises a plurality of conductive traces disposed on a multi-layer printed circuit board in a predetermined pattern.

5. The antenna system of claim 4 wherein the directional coupler is substantially lossless.

6. The antenna system of claim 1 wherein the directional coupler comprises a quadrature coupler.

7. The antenna system of claim 1 wherein coupling factors associated with the directional coupler equal in magnitude the mutual coupling between the corresponding antennas so that the amplitude of the antenna crosstalk signals and the amplitude of the coupled signals are substantially the same at the communication ports of the directional coupler.

8. The antenna system of claim 1 further comprising a plurality of receivers, each connected to a different communication port of the directional coupler.

9. A communication terminal comprising:

a directional coupler comprising multiple communication ports that each connect to a respective antenna port;

a plurality of transmitters, each connected to a different communication port of the directional coupler; and

a plurality of transmission lines, each connecting the antenna ports of the directional coupler to respective antennas, wherein the lengths of the transmission lines are selected to decouple the transmitters such that antenna crosstalk signals received during signal transmission and coupled signals produced by the directional coupler have opposite phase at the communication ports of the directional coupler.

10. The communication terminal of claim 9 wherein the selected transmission line lengths further enable the antenna crosstalk signals and the transmission signals to be in phase at the antenna ports of the directional coupler.

11. The communication terminal of claim 9 wherein the directional coupler comprises a plurality of conductive traces disposed on a multi-layer printed circuit board in a predetermined pattern.

12. The communication terminal of claim 11 wherein the directional coupler is substantially lossless.

13. The communication terminal of claim 9 wherein coupling factors associated with the directional coupler equal in magnitude the mutual coupling between the corresponding antennas so that the amplitude of the antenna crosstalk signals and the amplitude of the coupled signals are substantially the same at the communication ports of the directional coupler.

14. A communication terminal comprising:

a directional coupler comprising multiple communication ports that each connect to a respective antenna port;

a plurality of receivers, each connected to a different communication port of the directional coupler; and

a plurality of transmission lines connecting the antenna ports of the directional coupler to respective antennas, the lengths of the transmission lines selected such that antenna crosstalk signals caused by mutual coupling between the antennas and coupled signals produced by the directional coupler have opposite phase at the communication ports of the directional coupler.

15. The communication terminal of claim 14 wherein the selected transmission line lengths further enable the antenna crosstalk signals to be substantially in phase with the coupled signals at the antenna ports of the directional coupler.

16. The communication terminal of claim 14 wherein the directional coupler comprises a plurality of conductive traces disposed on a multi-layer printed circuit board in a predetermined pattern.

17. The communication terminal of claim 16 wherein the directional coupler is lossless.

18. The communication terminal of claim 14 wherein coupling factors associated with the directional coupler equal in magnitude the mutual coupling between the corresponding antennas.