Design and Verification of a Q-Band Test Source for UAV-Based Radiation Pattern Measurements

In the last years, the unmanned aerial vehicles (UAVs) generated significant innovations in in situ antenna measurements. UAV-mounted test sources have been exploited to characterize the radiation pattern of receiving antennas and arrays for HF radars, radio telescopes in very high-frequency (VHF) band, and up to the X-band for radar characterization. A UAV test source operating in the Q-band has been recently developed within the large-scale polarization explorer (LSPE) project. It will be used for the in situ validation of a ground-based cluster of coherent polarimeters for cosmology observation. This article presents the payload solution that is actually applicable to general UAV-based radiation pattern measurements in the Q-band. It is based on a phase-locked loop synthesizer and an active multiplier coupled with a power detector to compensate for signal power drifts in postprocessing. Relevant system tests have been performed in both laboratory environment and operative conditions. The measured outdoor radiation patterns are in good agreement with both the anechoic chamber measurements and simulated data.