Method and apparatus for testing phase shifter modules of a phased array antenna

• US 5,081,460 A
• Filed: 01/22/1991
• Issued: 01/14/1992
• Est. Priority Date: 01/22/1991
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Liu, Sien-Chang C.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US07/643,968
• Time in Patent Office: 357 Days
• Field of Search: 342/169, 342/170, 342/368, 342/369, 342/370, 342/371, 342/372, 342/373, 342/375, 342/376, 342/377
• US Class Current: 342/169
• CPC Class Codes: G01R 29/10 Radiation diagrams of antennas
• CPC Class Codes: G01S 7/4052 by simulation of echoes
• CPC Class Codes: G01S 7/4095 the external reference signals being modulated, e.g. rotating a dihedral reflector or modulating a transponder for simulation of a Doppler echo
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices

Abstract

Faulty subarray module circuit boards are detected in a phased array antenna having many subarray module circuit boards while the antenna is fully assembled and operationally integrated with a radar system. A far field ratio frequency test source illuminates the antenna. Binary digital signals that control subarray steering bits are set to a reference setting. A particular subarray module circuit board that is under test has its 180° main phase bit toggled between 0° and 180°. The radar selects the output of that particular subarray module by Doppler filter type of software filtering. The amplitude of the in-phase and quadrature phase signals from the radar is recorded. The binary digital signals that control subarray steering bits are set to a second setting. The 180° main phase bit of the module under test is again toggled between 0° and 180°. The output of the module under test is again selected by Doppler filter type of software filtering. The amplitude of the in-phase and quadrature phase signals from the radar is recorded. The phase difference from the reference setting to the second setting is computed and compared with a predetermined threshold. If desired, the test source may have a multi-element feed including multiple dipoles, each dipole having a radiation pattern wide enough to cover two rows of subarray modules, the test source being switched to the particular one of the dipoles that illuminates the row including the module under test.

Claims

1. A method for testing a phased array radar antenna having a plurality of subarray steering bit networks that provide subarray steering bits in unison in response to binary digital signals but that cannot be individually controlled, said method comprising the following steps:

illuminating the phased array radar antenna with a radio frequency test signal;

setting the binary digital signals that control subarray steering bits to a reference setting;

toggling the 180°

bit of the main phase bits of a subarray module under test between 0° and

180°

;

selecting the output of the subarray module under test by employing a predetermined filter;

setting the binary digital signals that control subarray steering bits to a second setting;

toggling the 180°

bit of the main phase bits of the subarray module under test between 0° and

180°

;

selecting the output of the subarray module under test by employing a predetermined filter; and

calculating the phase difference from the reference setting to the second setting and comparing it with a threshold.

2. The method of claim 1 which further comprises the step of recording the inphase and quadrature phase channel outputs from the radar receiver for each setting.

3. The method of claim 1 wherein each step of selecting the output of the subarray module comprises the step of selecting the output of the subarray module under test by employing Doppler filtering.

4. The method of claim 1 wherein each step of selecting the output of the subarray module comprises the step of selecting the output of the subarray module under test by employing a predetermined software filtering.

5. The method of claim 1 wherein each step of selecting the output of the subarray module comprises the step of selecting the output of the subarray module under test by employing a Doppler filter type of software filtering.

6. A method for testing a phased array radar antenna having a plurality of subarray steering bit networks that provide subarray steering bits in unison in response to binary digital signals but cannot be individually controlled, said method comprising the following steps:

illuminating the phased array radar antenna with a radio frequency test signal;

setting the binary digital signals that control subarray steering bits to a reference setting;

toggling the 180°

bit of the main phase bits of a subarray module under test between 0° and

180°

;

selecting the output of the subarray module under test by employing a Doppler filter type of software filtering;

recording the in-phase and quadrature phase channel outputs from the radar receiver;

setting the binary digital signals that control subarray steering bits to a second setting;

toggling the 180°

bit of the main phase bits of the subarray module under test between 0° and

180°

;

selecting the output of the subarray module under test by employing a Doppler filter type of software filtering;

recording the in-phase and quadrature phase channel outputs from the radar receiver; and

calculating the phase difference from the reference setting to the second setting and comparing it with a threshold.

7. Apparatus for testing subarray modules of a phased array antenna while it is integrated in a radar system comprising:

a phased array antenna comprising a plurality of subarray modules arrayed in a matrix pattern of rows and columns;

a radio frequency receiver coupled to said antenna for indicating the response of said subarray modules when illuminated with radio frequency energy;

a test source of radio frequency energy;

a multi-element feed comprising multiple dipoles coupled to said test source of radio frequency energy, and wherein said multi-element feed is disposed adjacent said phased array and having said phased array antenna aimed toward said multi-element feed, each dipole of said multi-element feed having a radiation pattern wide enough to cover two rows of said plurality of subarray modules, and wherein the test source is switchable to the particular one of said dipoles that illuminates the particular row of a particular one of said plurality of subarray modules that is under test.

8. The apparatus of claim 7 wherein said multi-element feed further comprises a mast and an RF cable coupled to said test source of radio frequency energy.

9. The apparatus of claim 7 wherein the phased array antenna has a plurality of subarray steering bit networks that provide subarray steering bits in unison in response to binary digital signals but that cannot be individually controlled.

10. The apparatus of claim 9 wherein the phased array antenna that is testable by:

illuminating the phased array antenna with a radio frequency test signal;

setting the binary digital signals that control subarray steering bits to a reference setting;

toggling the 180°

bit of the main phase bits of a subarray module under test between 0° and

180°

;

selecting the output of the subarray module under test by employing a predetermined filter;

setting the binary digital signals that control subarray steering bits to a second setting;

toggling the 180°

bit of the main phase bits of the subarray module under test between 0° and

180°

;

selecting the output of the subarray module under test by employing a predetermined filter; and

calculating the phase difference from the reference setting to the second setting and comparing it with a threshold.

11. The apparatus of claim 10 wherein the phased array antenna is further testable by recording the in-phase and quadrature phase channel outputs from the radar receiver for each setting.

12. The apparatus of claim 10 wherein the phased array antenna is further testable by selecting the output of the subarray module under test by employing Doppler filtering.

13. The apparatus of claim 10 wherein the phased array antenna is further testable by selecting the output of the subarray module under test by employing a predetermined software filtering.

14. The apparatus of claim 10 wherein the phased array antenna is further testable by selecting the output of the subarray module under test by employing a Doppler filter type of software filtering.