Antenna element self-test and monitoring

1. A method of testing a phased array antenna that includes a plurality of antenna element pairs, each antenna element pair of the plurality of antenna element pairs including a first antenna element and a second antenna element, said method comprising:

for each antenna element pair of the plurality of antenna element pairs, performing a first cross element gain measurement from the first antenna element to the second antenna element of that antenna element pair; and

determining whether there is a problem associated with the phased array antenna by examining the first cross element gain measurements for the plurality of antenna element pairs.

2. The method of claim 1 , further comprising:

for each antenna element pair of the plurality of antenna element pairs,

performing a second cross element gain measurement from the second antenna element to the first antenna element of that antenna element pair,

wherein determining whether there is a problem associated with the phased array antenna also involves examining the second cross element gain measurements for the plurality of antenna element pairs.

3. The method of claim 2 , wherein determining whether there is a problem associated with the phased array antenna also involves, for each antenna element pair among the plurality of antenna element pairs, comparing the first and second cross element gain measurements for that antenna element pair.

4. The method of claim 2 , further comprising:

for each antenna element pair of the plurality of antenna element pairs,

performing a first return loss measurement for the first antenna element of that antenna element pair and performing a second return loss measurement for the second antenna element of that antenna element pair,

wherein determining whether there is a problem associated with the phased array antenna also involves examining the first and second return loss measurements for the plurality of antenna element pairs.

5. The method of claim 2 , wherein, for each antenna element pair of the plurality of antenna element pairs, performing the first cross element gain measurement from the first antenna element to the second antenna element of that antenna element pair comprises measuring the power of a signal sent to the first antenna element of that antenna element pair and measuring the power received by the second antenna element of that antenna element pair.

6. The method of claim 2 , wherein within each antenna element pair among the plurality of antenna element pairs the first and second antenna elements of that pair are orthogonally oriented with respect to each other.

7. The method of claim 6 , wherein within each antenna element pair among the plurality of antenna element pairs the first and second antenna elements of that pair are cross-polarized (±45°) pairs.

8. The method of claim 6 , wherein within each antenna element pair among the plurality of antenna element pairs the first and second antenna elements of that pair are H—V polarized pairs.

9. An apparatus system comprising:

a phased array antenna comprising an array of antenna elements, the array of antenna elements forming a plurality of antenna element pairs, each antenna element pair of the plurality of antenna element pairs including a first antenna element and a second antenna element;

a plurality of transmitter circuits, each transmitter circuit of the plurality of transmitter circuits connected to a different corresponding one of the antenna elements within the array of antenna elements;

for each transmitter circuit among the plurality of transmitter circuits, a bidirectional coupler connected between that transmitter circuit and the antenna element to which that transmitter circuit is connected;

a detector system for measuring a signal characteristic;

a switching system for selectively connecting signals from the bidirectional couplers for the plurality of transmitter circuits to the detector system; and

a processor system programmed to use the switching system and the detector system to perform the operations of:

for each antenna element pair of the plurality of antenna element pairs, performing a first cross element gain measurement from the first antenna element to the second antenna element of that antenna element pair; and

determining whether there is a problem associated with the phased array antenna by examining the first cross element gain measurements for the plurality of antenna element pairs.

10. The apparatus of claim 9 , wherein the processor system is further programmed to use the switching system and the detector system to perform the operations of:

for each antenna element pair of the plurality of antenna element pairs,

performing a second cross element gain measurement from the second antenna element to the first antenna element of that antenna element pair; and

determining whether there is a problem associated with the phased array antenna by also examining the second cross element gain measurements for the plurality of antenna element pairs.

11. The apparatus of claim 10 , wherein the processor system is further programmed to determine whether there is a problem associated with the phased array antenna by also, for each antenna element pair among the plurality of antenna element pairs, comparing the first and second cross element gain measurements for that antenna element pair.

12. The apparatus of claim 10 , wherein the processor system is further programmed to use the switching system and the detector system to perform the operations of:

for each antenna element pair of the plurality of antenna element pairs,

performing a first return loss measurement for the first antenna element of that antenna element pair and performing a second return loss measurement for the second antenna element of that antenna element pair, and

determining whether there is a problem associated with the phased array antenna by also examining the first and second return loss measurements for the plurality of antenna element pairs.

13. The apparatus of claim 9 , wherein within each antenna element pair among the plurality of antenna element pairs, the first and second antenna elements of that pair are orthogonally oriented with respect to each other.

14. The apparatus of claim 13 , wherein within each antenna element pair among the plurality of antenna element pairs, the first and second antenna elements of that pair form a cross-polarized)(±45°) pair.

15. The apparatus of claim 13 , wherein within each antenna element pair among the plurality of antenna element pairs, the first and second antenna elements of that pair form a H—V polarized pair.

16. The apparatus of claim 10 , further comprising:

an RF pilot signal source;

for each transmitter circuit among the plurality of transmitter circuits, a directional coupler connected to supply a signal to that transmitter circuit; and

a second switching system for selectively connecting signals from the RF pilot signal source to the directional couplers for the plurality of transmitter circuits, and

wherein the processor system is further programmed to also use the RF pilot signal source and the second switching system to perform the operations of: for each antenna element pair of the plurality of antenna element pairs, performing the first cross element gain measurement from the first antenna element to the second antenna element of that antenna element pair and performing the second cross element gain measurement from the second antenna element to the first antenna element of that antenna element pair.

17. The apparatus of claim 16 , wherein the processor system is further programmed to also use the RF pilot signal source and the second switching system to perform the operations of:

for each antenna element pair of the plurality of antenna element pairs, performing a first return loss measurement for the first antenna element of that antenna element pair and performing a second return loss measurement for the second antenna element of that antenna element pair.