Method and apparatus for antenna calibration

1. A radio unit, comprising:

a plurality of transmit/receive (TX/RX) paths;

a plurality of radio frequency (RF) ports connected with the plurality of TX/RX paths;

a coupler, coupled with the plurality of TX/RX paths and configured to inject an uplink (UL) calibration signal into at least one of the plurality of RX paths, extract a downlink (DL) calibration signal from at least one of the plurality of TX paths, and extract transmit signal power from at least one of the plurality of TX paths to supervise a connection status between the radio unit and an antenna array;

wherein the coupler comprises a switch array connected to one TX/RX path of the plurality of TX/RX paths, and the one TX/RX path is reused, in a time division manner, for transmitting the UL calibration signal to the coupler, receiving the DL calibration signal from the coupler, and receiving the extracted transmit signal power from the coupler.

2. The radio unit of claim 1 , wherein the transmit signal power comprises a forward power and a reverse power.

3. The radio unit of claim 1 , further comprising:

a stand-alone TX/RX path, and

the coupler comprises a switch array connected to the stand-alone TX/RX path, and the stand-alone TX/RX path is used for transmitting the UL calibration signal to the coupler, receiving the DL calibration signal from the coupler, and receiving the extracted transmit signal power from the coupler.

4. The radio unit of claim 1 , when used in a frequency division duplex (FDD) system, the radio unit further comprises a transmitter observation receiver (TOR), and the coupler comprises a switch array connected to the TOR and to one TX path of the plurality of TX/RX paths, and the TX path is reused for transmitting the UL calibration signal to the coupler, and the TOR is used for receiving the DL calibration signal from the coupler and receiving the extracted transmit signal power from the coupler.

5. The radio unit of claim 1 , wherein the plurality of RF ports is configured to connect to a plurality of RF ports of an antenna array without RF cables.

6. A base station, comprising:

a radio unit of claim 1 ;

an antenna array having a plurality of RF ports;

wherein the plurality of RF ports connected with the plurality of RF ports of the radio unit without RF cables.

7. A method for calibrating an antenna array within a base station, wherein the base station comprises a radio unit, and the radio unit comprises a plurality of TX/RX paths, a plurality of RF ports connected with the plurality of TX/RX paths, and a coupler coupled with the plurality of TX/RX paths, the method comprising:

transmitting a UL calibration signal to at least one of the plurality of RX paths via the coupler;

receiving a DL calibration signal from at least one of the plurality of TX paths via the coupler;

determining, based on at least one of the UL calibration signal and the DL calibration signal, calibration coefficients of the at least one RX path and TX path; and

extracting transmit signal power from at least one of the plurality of TX paths to supervise a connection status between the radio unit and an antenna array;

wherein one of the plurality of TX/RX paths is reused, in a time division manner, for transmitting the UL calibration signal, receiving the DL calibration signal, and extracting the transmit signal power.

8. The method of claim 7 , wherein the UL calibration signal is transmitted to the coupler via one TX path of the plurality of TX/RX paths.

9. The method of claim 7 , wherein the UL calibration signal is transmitted to the coupler via a stand-alone transmitter path.

10. The method of claim 7 , wherein the DL calibration signal is transmitted from the coupler to one RX path of the plurality of TX/RX paths.

11. The method of claim 7 , wherein the DL calibration signal is transmitted from the coupler to a stand-alone receiver path.

12. The method of claim 7 , wherein the DL calibration signal is transmitted from the coupler to a transmitter observation receiver (TOR).