Phased array calibration and characterization based on orthogonal coding: Theory and experimental validation

This paper presents the Control Circuit Encoding (CCE) technique used for calibrating digitally controlled phased arrays. The CCE method employs sets of orthogonal codes that are sequentially applied to all attenuators and phase-shifters in the beamformer, allowing elements to be measured in-situ simultaneously with a calibration probe in the far or near field of the array. In addition to calibrating commanded gain & phase settings the technique enables the assessment of antenna array RMS gain & phase error, as well as fast and accurate measurement of in-situ element patterns and amplifier characteristics. The paper describes the theory and presents measured results performed on various active phased array antennas.