Method for calibrating an antenna system, control device, computer program and computer program products

• US 10,516,491 B2
• Filed: 06/08/2016
• Issued: 12/24/2019
• Est. Priority Date: 06/08/2016
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Jidhage, Henrik, Engdahl, Christer
• Primary Examiner(s): Le, Thanh C
• Application Number:
  US16/307,157
• Publication Number:
  US 20190149250A1
• Time in Patent Office: 1,294 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 number of antenna elements,

measuring the signal in two or more calibration antenna elements selected among remaining antenna elements of the number of 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 selected among the number of antenna elements and 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 at least the first set of corresponding number of measurement values and the second set of corresponding number of measurement values, thereby obtaining a first part of a correction matrix comprising for row i correction values for calibration antenna elements j relative to antenna element k with antenna element i being one of the first reference antenna element or the second 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 at least the first set of corresponding number of measurement values and the second set of corresponding number 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 being one of the first reference antenna element and the second 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 first respective constant c_i, i={1, . . . , N} and each column of the second part of the correction matrix is multiplied with a second 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

calculating a compensation value Δ

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

2. The method as claimed in claim 1, wherein the measuring of the signal is performed for each of the number of antenna elements not selected as the first reference antenna element when the signal is transmitted from the first reference antenna element or not selected as the second reference antenna element when the signal is transmitted from the second 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 number of antenna elements not selected as the first reference antenna element when the signal is transmitted from the first reference antenna element or not selected as the second reference antenna element when the signal is transmitted from the second reference antenna element.

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

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

R_ij^{k,Type 1} according to;

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

R_ij^{Type 2} according to;

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

7. The method as claimed in any claim 1, wherein the calculating of 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 non-transitory computer readable medium having a computer program stored thereon, the 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 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 number of antenna elements,

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

repeat the transmit and the measure at least for a second reference antenna element selected among the number of antenna elements and 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 at least the first set of corresponding number of measurement values and the second set of corresponding number of measurement values, thereby obtaining a first part of a correction matrix comprising for row i correction values for calibration antenna elements j relative to antenna element k with antenna element i being one of the first reference antenna element or the second 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 at least the first set of corresponding number of measurement values and the second set of corresponding number 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 being one of the first reference antenna element and the second 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 first respective constant c_i, i={1, . . . , N} and each column of the second part of the correction matrix is multiplied with a second 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.

11. The control device as claimed in claim 10, configured to measure the signal for each of the number of antenna elements not selected as the first reference antenna element when the signal is transmitted from the first reference antenna element or not selected as the second reference antenna element when the signal is transmitted from the second reference antenna element.

12. The control device as claimed in claim 10, configured to measure the signal only for neighboring elements selected among the number of antenna elements not selected as the first reference antenna element when the signal is transmitted from the first reference antenna element or not selected as the second reference antenna element when the signal is transmitted from the second reference antenna element.

13. The control device as claimed in claim 10, configured to calculate the correction value Δ

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

R_ij^{k,Type 1} according to;

14. The control device as claimed in claim 10, configured to calculate the correction value Δ

R_ij^{Type 2} for the second type of beamforming by calculating for correction branch j using element i being one of the first reference antenna element and the second reference antenna element, the correction value Δ

R_ij^{Type 2} according to;

15. The control device as claimed in claim 10, configured to perform the optimization procedure by performing a least square optimization by using expression:

16. The control device as claimed in claim 10, configured to calculate the compensation value by calculating an averaged compensation value Δ

r_i for each antenna element i by using equation;

17. The control device as claimed in claim 10, wherein the first type of beamforming is a standard beamforming and the second type of beamforming is a reciprocity based beamforming.