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In active phased array antennas, transmit and receive functions are distributed at the aperture using transmit and receive (T/R) modules. Active phased arrays are typically calibrated in a near-field antenna range at the factory. The performance of active phased array antennas would degrade over time due to changes in the characteristics of active devices and would require recalibration in the field. The conditions and methods required for the active phased-array antenna (APAA) measurements, initial alignment, further automatic diagnostics and performance monitoring are described. Special attention is paid to constructive peculiarities of APAA and measurement restrictions. A numerical model of performance monitoring process has been developed and many test cases examined in an effort to isolate and characterize errors commonly found in the built-in performance-monitoring systems (BPMS). Both simulation and measurement results are presented to demonstrate the utility of the proposed measurement and monitoring techniques. Future research directions in applying BPMS are highlighted.

active phased-array antenna; antenna measurements; automatic fault diagnostics; calibration; initial alignment; performance monitoring