System and method for active electronically scanned array test and calibration

1 . A test system for validating and calibrating an active electronically scanned array (AESA) having a plurality of distinct transceiver elements with associated RF channels, the test system comprising:

a static mount configured to fixedly receive the AESA;

at least one test probe fixedly located relative to the static mount and configured to transmit and receive complex radiation patterns to and from the AESA;

an RF measurement device communicatively coupled to the AESA and the at least one test probe, and configured to transmit and receive complex RF amplitudes and phases and/or time delays of the test probe and the AESA; and

a test processor communicatively connected to the RF measurement device, and configured to:

predict free space path losses and propagation delays between the AESA and the at the at least one probe based on radiation patterns of each and corresponding vectors defining known relative positions of the at least one test probe and each of the plurality of distinct transceiver elements;

estimate far field (FF) patterns of the AESA based on post-processing of the amplitudes and phases and/or time delays received via the RF measurement device, compensating for the predicted free space path losses and propagation delays;

calculate FF figures of merit (FoMs) for the AESA as a function of frequency, beam scan, and environmentals, based on the estimated FF patterns of the AESA; and

validate the AESA based on the FF FoMs.

2 . The test system of claim 1 , further comprising an anechoic enclosure surrounding the static mount and the at least one test probe.

3 . The test system of claim 2 , wherein the anechoic enclosure has width and height less than double corresponding dimensions of the AESA.

4 . The test system of claim 1 , wherein the test processor predicts the free space path losses and propagation delays via a Friis spatial transfer function.

5 . The test system of claim 1 , further comprising a beam steering controller (BSC) electronically connected to the AESA and operable to control beam-forming integrated circuits of each of the associated RF channels.

6 . The test system of claim 5 , wherein:

the test processor is configured to command the BSC to traverse of all permutations of the RF channels by incoherently driving the AESA through all amplitude and time-dependence states for each RF channels; and

estimating FF patterns of the AESA comprises analytically extrapolating from individual element analyses received from the RF measurement device to the FF pattern using Hadamard orthonormal transformations.

7 . The test system of claim 1 , wherein the RF measurement device is a precision vector RF measurement device configured for RF evaluation of coherently connected two-port transmit and receive parameters including the amplitudes and the phases and/or time delays.

8 . The test system of claim 1 , wherein the test processor is configured to iteratively repeat the estimation of FF patterns and the calculation of FF FoMs, and to adjust calibrations of the AESA between these iterations in response to the FF FoMs falling outside of accepted ranges, such that the validation occurs once any adjustments to the calibrations produce FF FoMs within the accepted ranges.

9 . The test system of claim 8 , wherein the calculation of FF FoMs comprises:

estimating first FoMs characterizing borescope FF performance of the AESA;

evaluating whether the first FoMs fall within first acceptable ranges; and

in response to the first FoMs falling within acceptable ranges, evaluating second FoMs characterizing the AESA over frequency and scan volume.

10 . The test system of claim 9 , wherein the calculation of FF FoMs further comprises:

evaluating whether the second FoMs fall within second acceptable ranges; and

in response to the second FoMs falling within acceptable ranges, evaluating third FoMs characterizing the AESA over environmentals including humidity, pressure, and temperature; and

evaluating whether the third FoMs fall within third acceptable ranges.

11 . The test system of claim 10 , wherein the test processor is configured to adjust element-level gains and/or phases of the RF channels in response to the first, second, or third FoMs falling outside of respective first, second, and third acceptable ranges.

12 . The test system of claim 2 , wherein the anechoic enclosure includes tools configured to control and sense multiple environmental parameters from among temperature, pressure, and humidity, within the anechoic isolating enclosure.

13 . A method of testing an AESA, the method comprising:

mounting the AESA and a test probe in a fixed geometric relationship, the AESA comprising a plurality of individual antenna elements with respective radiofrequency (RF) channels;

surrounding the AESA and the test probe in an anechoic enclosure;

collecting RF amplitudes and phases and/or time delays of the test probe and the AESA using a precision network analyzer (PNA);

predicting free space path losses and propagation delays between the AESA and the test probe based on the fixed geometric relationship;

estimating far field (FF) patterns of the AESA based on post-processing of the collected RF amplitudes and phases and/or time delays, and based on the predicted free space path losses and propagation delays;

calculating FF figures of merit (FoMs) for the AESA over frequency, beam scan, and environmentals based on the estimated FF patterns of the AESA.

14 . The method of claim 13 , further comprising evaluating the FF FoMs against acceptable ranges, and recalibrating the RF channels of the individual antenna elements of the AESA in response to the FF FoMs falling outside of the acceptable ranges.

15 . The method of claim 14 , wherein evaluating the FF FoMs comprises successively testing FF FoMs over frequency, then over frequency and beam scan, then over frequency, beam scan, and environmentals.

16 . The method of claim 13 , further comprising controlling at least one of humidity, temperature, and pressure within the enclosure, wherein calculating FF FoMs over environmentals comprises evaluating AESA performance at environmental conditions within the enclosure at selected values of humidity, temperature, and/or pressure.

17 . The method of claim 13 , wherein estimating FF patterns of the AESA comprises extrapolating from disentangled characterizations of the individual RF elements to an overall FF pattern based on orthonormal transformations.