Antenna array calibration

• US 6,157,343 A
• Filed: 04/21/1997
• Issued: 12/05/2000
• Est. Priority Date: 09/09/1996
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Ovesjo, Fredrik Bengt, Petersson, Sven Oscar, Andersson, Soren, Forssen, Ulf
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US08/844,638
• Time in Patent Office: 1,324 Days
• Field of Search: 342/174, 342/371, 342/372, 342/375, 342/173, 455/67.4
• US Class Current: 342/371
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices

Abstract

A method and a system for calibrating the reception and transmission of an antenna array for use in a cellular communication system is disclosed. The calibration of the reception of the antenna array is performed by injecting a single calibration signal into each of a number of receiving antenna sections, in parallel. The signals are collected after having passed receiving components that might have distorted the phase and amplitude. Correction factors are generated and applied to received signals. The calibration of the transmission of the antenna array is performed in a similar way. A single calibration signal is generated and injected into each of a number of transmitting antenna sections, one at a time. The signals are collected, one at a time, after having passed transmitting components that might have distorted the phase and amplitude. Correction factors are generated and applied to signals that are to be transmitted.

Claims

1. A method for calibrating an antenna array that receives communicated signals in a CDMA radio communication system, said antenna array comprising a number of receiving antenna sections each comprising receiving components that might distort the phase and the amplitude of received signals, said method comprising the steps of:

a) generating a single calibration signal;

b) injecting said calibration signal into each receiving antenna section, in parallel;

c) collecting a resulting calibration signal from each receiving antenna section after having passed the receiving components in each antenna section, in parallel, wherein the collected signals are modeled as complex data samples;

d) generating correction factors for each receiving antenna section based on said collected signals, wherein said correction factors are generated as complex factors; and

e) adjusting said receiving antenna sections with said correction factors, wherein the CDMA radio communication system has a predetermined number of codes that are allowed for use during normal traffic, wherein a code that is not intended to be used for traffic is used for calibration.

2. A method for calibrating an antenna array according to claim 1, wherein said step of injecting said calibration signal into each receiving antenna section comprises dividing said calibration signal into one divided signal for each receiving antenna section.

3. A method for calibrating an antenna array according to claim 2, wherein said calibration signal is divided into equal divided signals.

4. A method for calibrating an antenna array according to claim 1, wherein said generation of correction factors for each receiving antenna section comprises the steps of:

a) selecting one of the receiving antenna sections as a reference section;

c) determining a correction factor for the reference section; and

d) generating correction factors for the rest of the receiving antenna sections, relative the correction factor of the reference section.

5. A method for calibrating an antenna array according to claim 1, wherein said calibration signal is a pure sinusoid.

6. A method for calibrating an antenna array according to claim 1, wherein the collected signals are modeled as complex data samples, and wherein said correction factors are generated as complex factors.

7. A method for calibrating an antenna array according to claim 1, wherein said correction factors compensate for signal errors introduced by the receiving components in each antenna section, and for signal errors introduced by means used for calibrating the reception of the antenna array.

8. A method for calibrating an antenna array according to claim 1, wherein said correction factors preserve information about the initial power of the received signals.

9. A method for calibrating an antenna array according to claim 1, wherein said correction factors adjust the phase of signals received on each antenna section.

10. A method for calibrating an antenna array according to claim 1, wherein said correction factors adjust the amplitude of signals received on each of said antenna sections.

11. A method for calibrating an antenna array according to claim 1, wherein said correction factors adjust the phase and amplitude of signals received on said antenna sections.

12. A method for calibrating an antenna array according to claim 1, wherein the correction factors are applied to received signals before active beamforming.

13. A method for calibrating an antenna array according to claim 1, wherein the calibration method is performed during a limited amount of time on a traffic channel in use.

14. A method for calibrating an antenna array according to claim 1, wherein the calibration method is performed during a limited amount of time on a traffic channel between the termination of one call on said channel and the set up of another call on said channel.

15. A method for calibrating an antenna array according to claim 1, wherein the calibration signal is a low-power spread spectrum signal that is injected into the normal traffic flow.

16. A method for calibrating an antenna array according to claim 1, wherein said method is repeated at certain time intervals.

17. A method for calibrating an antenna array according to claim 1, wherein said method is continuously repeated.

18. A CDMA radio communication system for calibrating an antenna array that receives communicated traffic signals for beamforming in a mobile radio communication system, said antenna array comprising a number of receiving antenna sections each comprising receiving components that might distort the phase and the amplitude of received signals, said system comprising:

means for generating a single calibration signal;

means for injecting said calibration signal into each receiving antenna section, in parallel;

means for collecting a resulting calibration signal from each receiving antenna section after having passed the receiving components in each antenna section, in parallel;

means for generating correction factors for each receiving antenna section based on said collected signals, wherein said correction factors are applied to the traffic signals before the beamforming; and

means for adjusting said receiving antenna sections with said correction factors, without interrupting the communication in said communication system, wherein the CDMA radio communication system has a predetermined number of codes that are allowed for use during normal traffic, wherein a code that is not intended to be used for traffic is used for calibration.

19. A system for calibrating an antenna array according to claim 18, wherein said correction factors adjust the phase of signals received on each antenna section.

20. A system for calibrating an antenna array according to claim 18, wherein said correction factors adjust the amplitude of signals received on each of said antenna sections.

21. A system for calibrating an antenna array according to claim 18, wherein said correction factors adjust the phase and amplitude of signals received on said antenna sections.

22. A system for calibrating an antenna array according to claims 18, wherein the correction factors are applied to received signals before active beamforming.