METHOD, SYSTEM AND CALIBRATION TARGET FOR THE AUTOMATIC CALIBRATION OF AN IMAGING ANTENNA ARRAY

• US 20140247182A1
• Filed: 02/20/2013
• Published: 09/04/2014
• Est. Priority Date: 03/16/2012
• Status: Active Grant

• Current Assignee: Rohde & Schwarz GmbH & Company KG
• Original Assignee: Rohde & Schwarz GmbH & Company KG
• Inventors: Ahmed, Sherif Sayed
• Granted Patent: US 9,568,593 B2
• Time in Patent Office: Days
• US Class Current: 342/174
• CPC Class Codes: G01S 13/89 for mapping or imaging
• CPC Class Codes: G01S 7/4026 Antenna boresight
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices

Abstract

The system is used for the automatic calibration of an imaging array using an evaluation unit. The array transmits signals and receives the signals reflected from a calibration object of known shape. The calibration object provides at least one diffuse reflector. In the evaluation method, position coordinates of the calibration object are entered, and the following method steps are implemented after the measurement of the reflected signals: (i) calculate the reflections of the calibration object, (ii) calculate calibration data, (iii) prepare an image of the calibration object with the use of the calibration data, (iv) determine corrected position coordinates by evaluating the image of the at least one diffuse reflector, and (v) implement steps (i) to (iv) with corrected position coordinates.

Claims

1. A method for automatic calibration of an imaging array using an evaluation device, in which the imaging array transmits signals and receives signals reflected from a calibration object of known shape, wherein the calibration object provides at least one diffuse reflector, and wherein position coordinates of the calibration object are entered, the method comprising:

calculating the reflections of the calibration object;

calculating calibration data;

preparing an image of the calibration object with the use of the calibration data;

determining corrected position coordinates by evaluating the image of the at least one diffuse reflector; and

implementing the calculating, preparing, and determining steps with the corrected position coordinates.

2. The method according to claim 1, further comprising evaluating the image of the at least one diffuse reflector is evaluated with regard to brightness and/or resolution and/or distortion.

3. The method according to claim 2, wherein the evaluating step includes evaluating a distortion with regard to shape and orientation.

4. The method according to claim 1, wherein a numerical optimisation method is used to determine the corrected position coordinates.

5. The method according to claim 4, wherein the numerical optimisation method is applied to the image of respectively one diffuse reflector and/or several diffuse reflectors at the same time.

6. The method according to claim 3, wherein a gradient method or a heuristic algorithm is used as the optimisation method.

7. The method according to claim 1, wherein the position coordinates of the calibration object are defined by at least one spatial position.

17. The method according to claim 6, wherein the heuristic algorithm is a genetic optimisation algorithm.

18. The method according to claim 1, wherein the position coordinates of the calibration object are defined by the coordinates (x, y, z) and two angles of inclination (φ

_x-y, φ

_x-z).

8. A system for automatic calibration of an imaging array, comprising:

an evaluation device; and

a calibration object including a reflecting surface, which faces towards the imaging array, and at least one diffuse reflector directed towards the imaging array,

wherein the imaging array transmits signals and receives the signals reflected from the calibration object,

wherein the evaluation device evaluates the received signals, and

wherein the at least one diffuse reflector reflects in a diffuse manner signals which strike it.

9. The system according to claim 8, wherein the calibration object provides a flat surface and/or a cylindrical surface and/or an ellipsoid surface.

10. The system according to claim 8, wherein the at least one diffuse reflector is arranged on or near the reflecting surface.

11. The system according to claim 8, wherein at least one diffuse reflector is embodied as a needle-shaped, metallic or metallised pin and provides a tip, of which a spatial extension is in a same order of magnitude as a wavelength of the signals transmitted from the imaging array.

12. The system according to claim 8, wherein at least one diffuse reflector is embodied as a recess.

13. The system according to claim 8, wherein at least one diffuse reflector provides a round or cruciform contour.

14. The system according to claim 8, wherein the evaluation device includes provides:

an entry unit for entry of position coordinates of the calibration object,

a first calculation unit for calculating the reflections of the calibration object for the imaging array;

a second calculation unit for calculating calibration data;

an imaging unit for preparing an image of the calibration object using the calibration data;

a correction unit for determining corrected position coordinates by evaluating the image of the at least one diffuse reflector; and

an iteration unit which routes the corrected position coordinates once or several times to the first calculation unit.

15. The system according to claim 8, wherein the signals provide a frequency in the range between 30 GHz and 500 GHz.

19. The system according to claim 8, wherein the signals provide a frequency in the range between 50 GHz and 200 GHz.

16. A calibration object for automatic calibration of an imaging array with a reflecting surface comprising at least one diffuse reflector directed towards the imaging array on and/or near the reflecting surface, the at least one diffuse reflector reflecting in a diffuse manner signals which strike it,

wherein the diffuse reflector is embodied as a needle-shaped, metallic or metallised pin and provides a tip of which a spatial extension is in a same order of magnitude as a wavelength of the signals, and/or

wherein the diffuse reflector is embodied as a recess, and/or

wherein the diffuse reflector provides a material with a diffuse reflecting surface and provides a round or cruciform contour.