UAS-Based Antenna Pattern Measurements of the Fully Digital Horus Phased Array Radar

Fully digital phased array radars (PAR) are highly sophisticated systems that require accurate on-site assessments of each active element to produce the desired beam pattern. We present a novel approach to validate the antenna pattern by harnessing the capabilities of the Radio Frequency Sonde (RFSonde) uncrewed aerial system (UAS). This custom-made UAS performs pre-defined flight trajectories to evaluate power and reconstruct the radiation pattern in the far-field region of the radar. It is equipped with a modified 3-axis gimbal to ensure mechanical alignment with the antenna under testing, in line with the Ludwig-3 definition of cross-polarization [1]. Such an approach minimizes errors from the probe misalignment and maximizes the onboard power sensor's dynamic range. Through various field tests, the RFSonde has proven its effectiveness in validating radiation patterns by measuring both co-polar and cross-polar patterns of the S-band Horus PAR system [2]. The results of this work lay down the foundations to continue using UAS for on-site antenna pattern measurements leading to the formulation of methods to calibrate and validate polarimetric observations of PAR systems for weather research and applications.