METHOD FOR CALIBRATING AN ANTENNA SYSTEM, CONTROL DEVICE, COMPUTER PROGRAM AND COMPUTER PROGRAM PRODUCTS

• US 20190149250A1
• Filed: 06/08/2016
• Published: 05/16/2019
• Est. Priority Date: 06/08/2016
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: JIDHAGE, Henrik, ENGDAHL, Christer
• Granted Patent: US 10,516,491 B2
• Time in Patent Office: Days
• CPC Class Codes: H04B 17/12 of transmit antennas, e.g. of the amplitude or phase
• CPC Class Codes: H04B 17/19 Self-testing arrangements
• CPC Class Codes: H04B 7/0617 for beam forming

Abstract

A method of calibrating an antenna system comprising a number of antenna elements is provided. The method comprises transmitting and measuring at least for first and second reference antenna elements, thereby obtaining first and second sets of corresponding number of measurement values; calculating, for a first type of beamforming and for each calibration antenna element j a correction value—ΔR_ij^{k,Type 1}, thereby obtaining a first part of a correction matrix; calculating, for a second type of beamforming and for each branch j a correction value ΔR_i,j^{Type 2}, thereby obtaining a second part of the correction matrix; performing an optimization procedure using as input the correction matrix thereby obtaining, for each row of the correction matrix, a respective optimized constant, and calculating a compensation value Δr_i for each antenna element based on the respective optimized constant.

Claims

1. A method of calibrating an antenna system comprising a number of antenna elements, the method being performed in a control device and comprising:

transmitting a signal from a first reference antenna element selected among the antenna elements,

measuring the signal in two or more calibration antenna elements selected among the remaining antenna elements, and obtaining a first set of corresponding number of measurement values,

repeating the transmitting and measuring at least for a second reference antenna element different than the first reference antenna element, thereby obtaining a second set of corresponding number of measurement values,

calculating, for a first type of beamforming and for each calibration antenna element j a correction value Δ

R_ij^{k,Type 1}, based on the at least first and second sets of measurement values, thereby obtaining a first part of a correction matrix comprising for row i correction values for calibration antenna elements j relative antenna element k with antenna element i as the reference antenna element,

calculating, for a second type of beamforming and for each branch j a correction value Δ

R_i,j^{Type 2}, based on the at least first and second sets of measurement values, thereby obtaining a second part of the correction matrix comprising for row i correction values for branch j with antenna element i as the reference antenna element,

performing an optimization procedure using as input the correction matrix, wherein each column of the first part of the correction matrix, except one, is multiplied with a respective constant c_i, i={1, . . . , N} and each column of the second part of the correction matrix is multiplied with a respective constant c_i, i={N+1, . . . , 2N} thereby obtaining, for each row of the correction matrix, a respective optimized constant c₁^opt, and

calculating a compensation value Δ

r_i for each antenna element based on the respective optimized constant c₁^opt.

2. The method as claimed in claim 1, wherein the measuring the signal is performed for each of the antenna elements not selected as reference antenna element.

3. The method as claimed in claim 1, wherein the measuring the signal is performed only for neighboring elements selected among the antenna elements not selected as reference antenna element.

4. The method as claimed in claim 1, wherein the calculating the correction values Δ

R_ij^{k,Type 1} for the first type of beamforming comprises calculating for correction antenna element j relative antenna element k the correction values according to;

5. The method as claimed in claim 1, wherein the calculating the correction values Δ

R_ij^{Type 2} for the second type of beamforming comprises calculating for correction branch j using element i as reference element, the correction values according to;

6. The method as claimed in claim 1, wherein the performing the optimization procedure comprises performing a least square optimization comprises using expression:

7. The method as claimed in any claim 1, wherein the calculating the compensation value comprises calculating an averaged compensation value Δ

r_i for each antenna element i by using equation;

8. The method as claimed in claim 1, wherein the first type of beamforming is a standard beamforming and the second type of beamforming is a reciprocity based beamforming.

9. A computer program for a control device for calibrating an antenna system, the computer program comprising computer program code, which, when executed on at least one processor on the control device causes the control device to perform the method according to claim 1.

10. A computer program product comprising a computer program as claimed in claim 9 and a computer readable means on which the computer program is stored.

11. A control device for calibrating an antenna system comprising a number of antenna elements, the control device being configured to:

transmit a signal from a first reference antenna element selected among the antenna elements,

measure the signal in two or more calibration antenna elements selected among the remaining antenna elements, and obtaining a first set of corresponding number of measurement values,

repeat the transmitting and measuring at least for a second reference antenna element different than the first reference antenna element, thereby obtaining a second set of corresponding number of measurement values,

calculate, for a first type of beamforming and for each calibration antenna element j a correction value Δ

R_ij^{k,Type 1}, based on the at least first and second sets of measurement values, thereby obtaining a first part of a correction matrix comprising for row i correction values for calibration antenna elements j relative antenna element k with antenna element i as the reference antenna element,

calculate, for a second type of beamforming and for each branch j a correction value Δ

R_i,j^{Type 2}, based on the at least first and second sets of measurement values, thereby obtaining a second part of the correction matrix comprising for row i correction values for branch j with antenna element i as the reference antenna element,

perform an optimization procedure using as input the correction matrix, wherein each column of the first part of the correction matrix, except one, is multiplied with a respective constant c_i, i={1, . . . , N} and each column of the second part of the correction matrix is multiplied with a respective constant c_i, i={N+1, . . . , 2N} thereby obtaining, for each row of the correction matrix, a respective optimized constant c_i^opt, and

calculate a compensation value Δ

r_i for each antenna element based on the respective optimized constant c_i^opt.

12. The control device as claimed in claim 11, configured to measure the signal for each of the antenna elements not selected as reference antenna element.

13. The control device as claimed in claim 11, configured to measure the signal only for neighboring elements selected among the antenna elements not selected as reference antenna element.

14. The control device as claimed in claim 11, configured to calculate the correction values Δ

R_ij^{k,Type 1} for the first type of beamforming by calculating for correction antenna element j relative antenna element k the correction values according to;

15. The control device as claimed in claim 11, configured to calculate the correction values Δ

R_ij^{Type 2} for the second type of beamforming by calculating for correction branch j using element i as reference element, the correction values according to;

16. The control device as claimed in claim 11, configured to perform the optimization procedure comprises performing a least square optimization by using expression:

17. The control device as claimed in claim 11, configured to calculate the compensation value by calculating an averaged compensation value Δ

r_i for each antenna element i by using equation;

18. The control device as claimed in claim 11,

wherein the first type of beamforming is a standard beamforming and the second type of beamforming is a reciprocity based beamforming.