Local compensation of failed elements of an active antenna array

• US 5,083,131 A
• Filed: 05/31/1990
• Issued: 01/21/1992
• Est. Priority Date: 05/31/1990
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Julian, Michael D.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US07/531,200
• Time in Patent Office: 600 Days
• Field of Search: 342/372, 342/373, 342/174, 342/165, 342/173
• US Class Current: 342/372
• CPC Class Codes: G01S 7/2813 Means providing a modification of the radiation pattern for cancelling noise, clutter or interfering signals, e.g. side lobe suppression, side lobe blanking, null-steering arrays specially adapted to secondary radar systems G01S13/762; aerials or aerials systems H01Q21/29, H01Q25/00
• CPC Class Codes: G01S 7/4004 of parts of a radar system
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices

Abstract

Compensation for a failed element of an active antenna array is acheived by turning the failed element off and selecting a plurality of adjacent, properly working elements as local compensators. A selected voltage and phase increment is then added to the complex output voltage which each local compensator would normally produce. The magnitude of the voltage increment is selected by dividing the magnitude of the failed element'"'"'s voltage, were it not failed, by the number of compensators. The phase increment is selected to scan the associated voltage increment at a depression angle of about 30 degrees below the horizon.

Claims

1. A method for compensating for a failed element of an active antenna array, said array including said failed element and a plurality of adjacent elements, said method comprising the steps of:

turning the failed element off;

selecting a plurality of said adjacent elements as local compensators; and

adjusting the phase and voltage of each local compensator to compensate for said failure.

2. The method of claim 1 wherein the step of adjusting the phase and voltage includes the steps of dividing the magnitude of the voltage signal which would have been radiated by the failed element if it were working properly by the number of said local compensators to determine a voltage factor by which to increment the voltage of the signal radiated by each local compensator.

3. The method of claim 1 wherein the step of adjusting the phase and voltage further includes the step of determining a selected phase to be assigned to each local compensator.

4. The method of claim 2 wherein the step of adjusting the phase and voltage further includes the step of determining a selected phase increment assigned to each said voltage factor.

5. The method of claim 3 wherein said selected phase is determined so as to scan the voltage increment at a selected depression angle.

6. The method of claim 3 wherein said step of determining a selected phase further includes the step of determining a first phase increment by adding the phase of the original failed element to a phase increment Δ

φ and

determining a second phase increment by subtracting Δ

φ

from the phase of the original failed element.

7. The method of claim 6 wherein said phase increment Δ

φ

is determined according to the equation;

##EQU13## where s is the vertical spacing of the compensating elements above and below the failure;

λ

is the wavelength of the emitted signal; and

θ

is a desired depression angle.

8. The method of claim 7 wherein the desired depression angle θ

is 30 degrees.

9. The method of claim 4 wherein the selected voltage at the selected phase for each respective local compensator are added to the original complex voltage assigned to the respective local compensator to form an adjusted compensator voltage.

10. The method of claim 7 wherein the selected voltage at the selected phase for each respective local compensator are added to the original complex voltage assigned to the respective local compensator to form an adjusted compensator voltage.

11. The method of claim 9 wherein, if the magnitude of the adjusted compensator voltage exceeds the saturation amplitude of the local compensator element, the magnitude of the adjusted compensator voltage is set to said saturation value.

12. The method of claim 10 wherein, if the magnitude of the adjusted compensator voltage exceeds the saturation amplitude of the local compensator element, the magnitude of the adjusted compensator voltage is set to said saturation value.

13. The method of claim 1 wherein said failed element and the plurality of adjacent elements is a diamond lattice with said failed element lying at the intersection of first and second diagonal line segments, said local compensators comprising first, second, third, and fourth said elements, one disposed at each end of said first and second line segments.

14. The method of claim 11 wherein said failed element and the plurality of adjacent elements is a diamond lattice with said failed element lying at the intersection of first and second diagonal line segments, said local compensators comprising first, second, third, and fourth said elements, one disposed at each end of said first and second line segments.

15. The method of claim 1 wherein said failed element and the plurality of adjacent elements is a rectangular lattice comprising a matrix of rows and columns of elements and wherein a single element immediately above said failed element and a single element immediately below said failed element are selected as local compensators.

16. The method of claim 11 wherein said failed element and the plurality of adjacent elements is a rectangular lattice comprising a matrix of rows and columns of elements and wherein a single element immediately above said failed element and a single element immediately below said failed element are selected as local compensators.

17. The method of claim 1 wherein said step of locating includes the steps of:

evaluating the performance of a plurality of modules of said array, wherein said step of evaluating comprises the steps of;

determining an FFT power spectrum related to the operation of said module, said spectrum including a power component related to the module under test and a plurality of additional power components; and

comparing selected said components to evaluate the performance of said module.

18. The method of claim 1 wherein each element of said array includes a transmit phase shifter and a receive phase shifter, and said step of locating includes the step of testing each element of the array to detect a failed element, each element being tested by:

turning off all elements of the array but one, said one element comprising an element under test;

cycling said element under test through alternating receive and transmit states;

shifting the phase of the element under test after each successive pair of receive and transmit states;

sampling first and second signals, the first signal being representative of the transmit phase shifter output, the second signal being representative of the receive phase shifter output, said first signal being sampled during each transmit state, said second signal being sampled during each receive state;

collecting the output samples taken in the receive state into a first set and those taken in the transmit state into a second set;

determining the average power in a succession of Fourier transform filters taken over the samples of said first set;

determining the average power in a succession of Fourier transform filters taken over the samples of said second set; and

comparing the power in selected said filters and rejoicing the element under test as failed based upon said comparison.

19. The method of claim 18 wherein said samples comprise the output of a receiver supplied with in-phase and quadrature phase signals and wherein one output sample is collected for each phase state through which the element under test is shifted for both the transmit and receive states.