Bench-top measurement method, apparatus and system for phased array radar apparatus calibration

• US 8,686,896 B2
• Filed: 02/11/2011
• Issued: 04/01/2014
• Est. Priority Date: 02/11/2011
• Status: Active Grant

• Current Assignee: SRC, Inc.
• Original Assignee: SRC, Inc.
• Inventors: Schuman, Harvey K., Davis, Anthony M., McPherson, Donald M., Robinson, Michael, Hagenmayer, David R., Wiley, John G.
• Primary Examiner(s): GREGORY, BERNARR E
• Application Number:
  US13/025,652
• Publication Number:
  US 20120206291A1
• Time in Patent Office: 1,145 Days
• Field of Search: 342165-175, 342/195, 342/360, 342368-377, 342 73- 82, 342/89, 342/350, 343/700.R, 343/703, 702/85, 702/106, 702/127, 702182-185
• US Class Current: 342/173
• CPC Class Codes: G01S 2013/0245 Radar with phased array antenna
• CPC Class Codes: G01S 7/4026 Antenna boresight
• CPC Class Codes: G01S 7/403 in azimuth, i.e. in the horizontal plane
• CPC Class Codes: G01S 7/4034 in elevation, i.e. in the vertical plane
• CPC Class Codes: H01Q 21/205 providing an omnidirectional coverage turnstile aerials H01Q21/26
• CPC Class Codes: H01Q 3/242 Circumferential scanning
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices

Abstract

A method for determining beamformer scattering parameters for a plurality of phased array radar antenna subarrays that each include a radiating (e.g., dipole) component and a beamformer component provides for obtaining for the plurality of phased array radar antenna subarrays a plurality of electromagnetic measurements at a plurality of ports. Analogous electromagnetic measurements are obtained for a reference subarray including a radiating component but absent a beamformer component. The plurality of phased array radar antenna subarray electromagnetic measurements and the reference subarray electromagnetic measurements provide a plurality of beamformer scattering parameter values for the plurality of phased array radar antenna subarrays that may be used in modeling and calibrating a phased array radar apparatus that may be assembled from the plurality of phased array radar antenna subarrays.

Claims

1. A method for determining scattering parameters for an operational phased array radar antenna subarray, the method comprising the steps of:

measuring, using a reference subarray that includes a dipole component but not a beamformer component, values for a plurality of reference electromagnetic parameters;

measuring, using an operational phased array radar antenna subarray that includes the dipole component and the beamformer component, values for a plurality of operational electromagnetic parameters; and

calculating from the values for the plurality of operational electromagnetic parameters and the values for the plurality of reference electromagnetic parameters beamformer scattering parameters for the operational phased array radar antenna subarray.

2. The method of claim 1 wherein the plurality of reference electromagnetic parameters includes reference port parameter signals.

3. The method of claim 1 wherein the plurality of operational electromagnetic parameters includes operational port parameter signals.

4. The method of claim 1 wherein the measuring the values for the plurality of reference electromagnetic parameters and the measuring the values for the plurality of operational electromagnetic parameters is undertaken in an electrical test apparatus that electromagnetically energizes one test port and measures a signal at the remaining test ports.

5. The method of claim 1 wherein the calculating uses the equation:

B_cd=T_ca(T_aa−

S_aa+S_adS<sup>−

1</sup>_ddS_da)<sup>−

1</sup>S_adS<sup>−

1</sup>_dd

where;

B, S and T denote scattering parameter row (B_cd, T_ca) and square (S_aa, T_aa, S_ad, S_dd, S_da) matrices with identical normalizing impedances; and

subscripts xy, where x and y are independently a, c and d, are reflected signal at the x port with respect to incident signal at the y port.

6. The method of claim 1 wherein the calculating uses the equation:

B_dd=[S_da(T_aa−

S_aa)<sup>−

1</sup>S_ad+S_dd]¹

where;

B, S and T denote scattering parameter square matrices with identical normalizing impedances; and

subscripts xy, where x and y are independently a, c and d, are reflected signal at the x port with respect to incident signal at the y port.

7. The method of claim 1 wherein the calculating uses the equation:

B_dd=[S_ad+(T_aa−

S_aa)S<sup>−

1</sup>_daS_dd]<sup>−

1</sup>(T_aa−

S_aa)S<sup>−

1</sup>_da

where;

B, S and T denote scattering parameter square matrices with identical normalizing impedances; and

subscripts xy, where x and y are independently a, c and d, are reflected signal at the x port with respect to incident signal at the y port.

8. A method for calibrating a phased array radar, the method comprising the steps:

measuring, using a reference subarray that includes a dipole component but not a beamformer component reference array port, parameter signals for the reference subarray;

measuring, for each of a plurality of operational phased array radar antenna subarrays each of which include the dipole component and the beamformer component, a corresponding plurality of operational array port parameter signals for the plurality of operational phased array radar antenna subarrays;

calculating for the plurality of operational phased array radar antenna subarrays a corresponding plurality of calculated beamformer parameters from the reference array port parameter signals and the plurality of operational phased array antenna subarray port parameter signals; and

using the plurality of calculated beamformer parameter values for the plurality of operational phased array radar antenna subarrays in a general electromagnetic analysis model to determine modeled radar performance characteristics for a phased array radar comprising the plurality of operational phased array radar antenna subarrays.

9. The method of claim 8 further comprising correlating the modeled radar performance characteristics with a look-up table to calibrate the phased array radar.

10. The method of claim 8 wherein the calculated beamformer parameters comprise beamformer scattering parameters for the plurality of operational phased array radar antenna subarrays.

11. The method of claim 8 wherein the general electromagnetic model uses a computational electromagnetic analysis computer code.

12. The method of claim 8 wherein the calculating uses the equation:

B_cd=T_ca(T_aa−

S_aa+S_adS<sup>−

1</sup>_ddS_da)<sup>−

1</sup>S_adS<sup>−

1</sup>_dd

where;

B, S and T denote scattering parameter row (B_cd, T_ca) and square (S_aa, T_aa, S_ad, S_dd, S_da) matrices with identical normalizing impedances; and

subscripts xy, where x and y are independently a, c and d, are reflected signal at the x port with respect to incident signal at the y port.

13. The method of claim 8 wherein the calculating uses the equation:

B_dd=[S_da(T_aa−

S_aa)<sup>−

1</sup>S_ad+S_dd]<sup>−

1</sup>

where;

B, S and T denote scattering parameter square matrices with identical normalizing impedances; and

subscripts xy, where x and y are independently a, c and d, are reflected signal at the x port with respect to incident signal at the y port.

14. The method of claim 8 wherein the calculating uses the equation:

B_dd=[S_ad+(T_aa−

S_aa)S<sup>−

1</sup>_daS_dd]<sup>−

1</sup>(T_aa−

S_aa)S<sup>−

1</sup>_da

where;

B, S and T denote scattering parameter square matrices with identical normalizing impedances; and

subscripts xy, where x and y are independently a, c and d, are reflected signal at the x port with respect to incident signal at the y port.

15. A test apparatus comprising:

an array of test ports that terminate with an array of test dipoles that mate with an array of dipoles on a phased array radar antenna subarray; and

means for energizing one of the test ports with an external signal while measuring a response to the external signal at the remainder of the test ports.

16. The test apparatus of claim 15 wherein the phased array radar antenna subarray is separate from a phased array radar apparatus.

17. A test system comprising:

a test apparatus comprising;

an array of test ports that terminate with an array of test dipoles that mate with an array of dipoles on a phased array radar antenna subarray; and

means for energizing one of the array of test ports with an external signal while measuring a response to the external signal at the remainder of the test ports; and

a computer programmed for calculating values for beamformer scattering parameters from the external signal and the response to the external signal.

18. The test system of claim 17 wherein the calculating uses the equation:

B_cd=T_ca(T_aa−

S_aa+S_adS<sup>−

1</sup>_ddS_da)<sup>−

1</sup>S_adS<sup>−

1</sup>_dd

where;

B, S and T denote scattering parameter row (B_cd, T_ca) and square (S_aa, T_aa, S_ad, S_dd, S_da) matrices with identical normalizing impedances; and

subscripts xy, where x and y are independently a, c and d, are reflected signal at the x port with respect to incident signal at the y port.

19. The test system of claim 17 wherein the calculating uses the equation:

B_dd=[S_da(T_aa−

S_aa)<sup>−

1</sup>S_ad+S_dd]<sup>−

1</sup>

where;

B, S and T denote scattering parameter square matrices with identical normalizing impedances; and

subscripts xy, where x and y are independently a, c and d, are reflected signal at the x port with respect to incident signal at the y port.

20. The test system of claim 17 wherein the calculating uses the equation:

B_dd=[S_ad+(T_aa−

S_aa)S<sup>−

1</sup>_daS_dd]<sup>−

1</sup>(T_aa−

S_aa)S<sup>−

1</sup>_da

where;

B, S and T denote scattering parameter square matrices with identical normalizing impedances; and

subscripts xy, where x and y are independently a, c and d, are reflected signal at the x port with respect to incident signal at the y port.