Calibration of differential frequency-dependent characteristics of a radio communications system

• US 6,570,527 B1
• Filed: 09/28/2001
• Issued: 05/27/2003
• Est. Priority Date: 09/28/2001
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: ArrayComm LLC (Ygomi LLC)
• Inventors: Lindskog, Erik D., Trott, Mitchell D., Kerr, Adam B.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US09/967,258
• Time in Patent Office: 606 Days
• Field of Search: 342/42-52, 342/57, 342/58, 342/165, 342/173, 342/174, 342/175, 342/195, 342/368-377, 370/315-325, 370/328, 370/329, 370/335, 370/342, 370/343-350
• US Class Current: 342/174
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices
• CPC Class Codes: H04B 17/12 of transmit antennas, e.g. of the amplitude or phase
• CPC Class Codes: H04B 17/21 for calibration; for correcting measurements
• CPC Class Codes: H04B 7/0613 using simultaneous transmission H04B7/0686 takes precedence
• CPC Class Codes: H04B 7/0837 using pre-detection combining H04B7/0868 takes precedence
• CPC Class Codes: H04B 7/12 Frequency diversity

Abstract

A method and apparatus are provided that determine a frequency dependent calibration vector for a set of transmit or receive chains of a radio communications system using only differential phase and amplitude between the transmit chains and the receive chains, respectively. In one embodiment, the invention includes an antenna array adapted to transmit and receive radio communications signals with a plurality of other terminals, a transmit chain to transmit a calibration signal through the antenna array to a transponder on at least two different frequency bands, and a receive chain to receive through the antenna array a transponder signal from the transponder, the transponder signal being received on at least two different frequency bands and being based on the calibration signal. A signal processor determines a frequency dependent calibration vector based on the at least two frequency bands of the transponder signal as received through the receive chain by comparing relative characteristics for the transponder signal at a first one of the at least two frequencies to relative characteristics for the transponder signal at a second one of the at least two frequencies.

Claims

1. A radio communications system comprising:

an antenna array adapted to transmit and receive radio communications signals with a plurality of other terminals;

a transmit chain to transmit a calibration signal through the antenna array to a transponder on at least two different frequency bands;

a receive chain to receive through the antenna array a transponder signal from the transponder, the transponder signal being received on at least two different frequency bands and being based on the calibration signal; and

a signal processor to determine a frequency dependent calibration vector based on the at least two frequency bands of the transponder signal as received through the receive chain by comparing relative characteristics for the transponder signal at a first one of the at least two frequencies to relative characteristics for the transponder signal at a second one of the at least two frequencies.

2. The system of claim 1, wherein determining a frequency dependent calibration vector comprises comparing relative phases for the transponder signal at a first one of the at least two frequencies to relative phases for the transponder signal at a second one of the at least two frequencies to determine a group delay.

3. The system of claim 1, wherein the transponder signal is shifted in frequency as compared to the calibration signal.

4. The system of claim 1, wherein the relative characteristics comprise the relative phases and amplitudes of the transponder signal as received by the receive chain.

5. The system of claim 4:

wherein the receive chain comprises a plurality of receive chains;

wherein each receive chain receives the transponder signal;

wherein the frequency dependent calibration vector comprises group delay; and

wherein the signal processor determines a group delay by comparing the relative phases and amplitudes of the transponder signal at each frequency as received by each receive chain.

6. The system of claim 5 wherein determining a frequency dependent calibration vector comprises determining a receive chain group delay by comparing a phase difference between at least two receive chains for the transponder signal at a first one of the at least two frequency bands to a phase difference between the same two receive chains for the transponder signal at a second one of the at least two frequency bands.

7. The system of claim 6, wherein one of the plurality of receive chains is selected as a reference receive chain and the group delay for each receive chain is characterized with respect to the reference receive chain.

8. The system of claim 4 wherein the relative characteristics comprise measured phases and amplitudes of the transponder signal, wherein the signal processor determines an uplink signature of the transponder at the antenna array at each frequency of the transponder signal using the measured phases and amplitudes of the transponder signal and wherein the signal processor determines the frequency dependent calibration vector for the receive chain using the uplink signatures of the transponder.

9. The system of claim 4 wherein the relative characteristics comprise measured phases and amplitudes of the transponder signal, wherein the signal processor determines a downlink signature of the transmit chain at the transponder using measured phases and amplitudes at each frequency of the transponder signal and wherein the signal processor further determines the frequency dependent calibration vector for the transmit chain using the downlink signatures of the transmit chain.

10. The system of claim 4:

wherein the transmit chain comprises a plurality of transmit chains;

wherein each transmit chain transmits the calibration signal;

wherein the frequency dependent calibration vector comprises group delay; and

wherein the signal processor determines a frequency dependent transmit calibration vector by comparing the relative phases of the transponder signal at each frequency of the transponder signal as received by each receive chain.

11. The system of claim 10, wherein the calibration signal comprises a plurality of signals, one from each transmit chain, each signal being individually identifiable based on a unique modulation sequence.

12. The system of claim 10 wherein determining a frequency dependent transmit calibration vector comprises comparing a phase difference between two transmit chains for the transponder signal at a first one of the at least two frequencies to a phase difference between the same two transmit chains for the transponder signal at a second one of the at least two frequencies to determine a group delay.

13. The system of claim 12 wherein one of the plurality of transmit chains is selected as a reference chain and the group delay of each transmit chain is defined with respect to the reference chain.

14. The system of claim 1, wherein the radio communication signals are adapted to conform to a code division multiple access standard.

15. A machine-readable medium having stored thereon data representing instructions which, when executed by a machine, cause the machine to perform operations comprising:

transmitting radio communications signal to a plurality of other terminals using a transmit chain;

receiving radio communications signals from a plurality of other terminals using a receive chain;

transmitting a calibration signal through transmit chain to a transponder on at least two different frequency bands;

receiving a transponder signal from the transponder, the transponder signal being received on at least two different frequency bands and being based on the calibration signal; and

determining a frequency dependent calibration vector based on the at least two frequency bands of the transponder signal as received through the receive chain by comparing relative characteristics for the transponder signal at a first one of the at least two frequencies to relative characteristics for the transponder signal at a second one of the at least two frequencies.

16. The medium of claim 15, wherein determining a frequency dependent calibration vector comprises comparing relative phases for the transponder signal at a first one of the at least two frequencies to relative phases for the transponder signal at a second one of the at least two frequencies to determine a group delay.

17. The medium of claim 16, wherein the relative characteristics comprise measured phases and amplitudes of the transponder signal, wherein the instructions, when executed by the machine, cause the machine to determine an uplink signature of the transponder at the antenna array at each frequency of the transponder signal using the measured phases and amplitudes of the transponder signal and wherein the instructions, when executed by the machine, cause the machine to determine the frequency dependent calibration vector for the receive chain using the uplink signatures of the transponder.

18. The medium of claim 15, wherein the relative characteristics comprise the relative phases and amplitudes of the transponder signal as received by the receive chain.

19. The medium of claim 18 wherein determining a frequency dependent calibration vector comprises determining a receive chain group delay by comparing a phase difference between at least two receive chains for the transponder signal at a first one of the at least two frequency bands to a phase difference between the same two receive chains for the transponder signal at a second one of the at least two frequency bands.

20. The medium of claim 19, wherein one of the plurality of receive chains is selected as a reference receive chain and the group delay for each receive chain is characterized with respect to the reference receive chain.

21. The medium of claim 15, wherein the radio communication signals are adapted to conform to a code division multiple access standard.

22. A method comprising:

transmitting radio communications signal to a plurality of other terminals using a transmit chain;

receiving radio communications signals from a plurality of other terminals using a receive chain;

transmitting a calibration signal through the transmit chain to a transponder on at least two different frequency bands;

receiving a transponder signal from the transponder, the transponder signal being received on at least two different frequency bands and being based on the calibration signal; and

determining a frequency dependent calibration vector based on the at least two frequency bands of the transponder signal as received through the receive chain by comparing relative characteristics for the transponder signal at a first one of the at least two frequencies to relative characteristics for the transponder signal at a second one of the at least two frequencies.

23. The method of claim 22, wherein determining a frequency dependent calibration vector comprises comparing relative phases for the transponder signal at a first one of the at least two frequencies to relative phases for the transponder signal at a second one of the at least two frequencies to determine a group delay.

24. The method of claim 22 wherein the relative characteristics comprise measured phases and amplitudes of the transponder signal, the method further comprising determining a downlink signature of the transmit chain at the transponder using measured phases and amplitudes at each frequency of the transponder signal and determining the frequency dependent calibration vector for the transmit chain using the downlink signatures of the transmit chain.

25. The method of claim 22 wherein determining a frequency dependent transmit calibration vector comprises comparing a phase difference between two transmit chains for the transponder signal at a first one of the at least two frequencies to a phase difference between the same two transmit chains for the transponder signal at a second one of the at least two frequencies to determine a group delay.

26. The method of claim 22, wherein the radio communication signals are adapted to conform to a code division multiple access standard.