Built-in test systems of active phased-array antennas

In the active phased array antennas, transmit and receive functions are distributed over the aperture using transmit and receive (T/R) modules. Active phased arrays are typically calibrated in the near-field antenna range on a factory. The performance of the active phased array antennas degrades over the course of time due to the changes in the characteristics of active devices and it requires recalibration in the field. The conditions and methods required for the measurements of the active phased-array antennas (APAA), the initial alignment, the automatic diagnostics and performance monitoring are described. Special attention is given to the constructive peculiarities of APAA and restrictions of measurements. A numerical model of a process of performance monitoring has been developed and a large number of test cases examined in order to isolate and characterize errors commonly occured in the built-in performance-monitoring systems (BPMS). The test methods used for APAA transmit or receive performance testing must be analyzed separately. During the alignment and testing of APAA, especially with high-power transmitting potential, it is necessary to fulfill some special requirements of measurement facilities and analytical software that are not encountered in other areas of applications of antenna measurements. Either simulation or measurement results are presented to demonstrate the utility of the proposed measuring and monitoring techniques. Future directions of investigation of application of BPMS are highlighted.