Absolute RCS Calibration of a UAV Ultrawideband Surface Penetrating Radar Using a Disk

Recent advancements in the uncrewed aerial vehicles (UAVs) as remote system platforms have enabled low-cost and easy-to-use options for various applications. An example of such a remote sensing system is a software-defined radar (SDRadar) mounted on a UAV. There is a need to accurately calibrate the radar system with low-cost and field-ready schemes to utilize the full potential of the radar system. Our system is an SDRadar mounted on a small UAV. The waveform of the radar has a 1-GHz bandwidth with a center frequency set to 750 MHz. The calibration employs a 59-cm-diameter disk elevated above the ground as an external passive target. Our results demonstrate a calibration accuracy of approximately 1 dB across most of the transmitted band, in both laboratory and field conditions. However, calibration challenges persist in the lowest parts of the frequency range, which are affected by the high side lobes and grating lobes in the antenna pattern. This calibration process is adaptable to various bandwidths and center frequencies.