In-situ, high-resolution radar imaging of dynamic targets using an ultra-wideband radar
This dissertation investigates in-situ, high-resolution radar imaging of dynamic targets using an ultra-wideband (UWB) radar. Three challenging classes of dynamic targets are investigated: wind turbines, vehicles, and small consumer drones. First, the measurement and processing methodologies are developed to capture the inverse synthetic aperture radar (ISAR) image of an operating horizontal-axis wind turbine. Measurement data of a small three-blade wind turbine are collected using a UWB radar, and the measured signatures are compared to simulation results based on physical optics. The backscattering phenomenology is examined in the sinogram, spectrogram, and ISAR image domains. The same methodologies are then applied to generate the in-situ ISAR imagery of an 18-blade windmill and a 1.7 MW utility-class wind turbine. Next, the radar signatures of a vertical-axis wind turbine are studied. Measurement and simulation are carried out for a 1.5 m tall Darrieus-type turbine model. Interpretation of the dominant backscattering mechanisms is carried out. Subsequently, the radar signatures of a 112 m tall turbine are examined using simulation. Second, wide-angle ISAR imaging of vehicles is investigated. Measurement data of moving vehicles are collected using a stationary roadside UWB radar. The generated baseline ISAR images show a clear distinction between different-sized vehicles. The images are further focused through motion compensation using a p-norm minimization. The resulting images are well focused and correspond closely to the physical dimensions of the vehicles. Third, the ISAR imaging of small consumer drones is considered. Laboratory measurement is conducted first, where the drones are rotated on a turntable and the backscatterered data are collected over a wide frequency band to form high-resolution images. The effects of frequency band, aspect, polarization, dynamic blade rotation, camera mount, and drone types are examined. Subsequently, ISAR imaging of in-flight drones, from data collected using a stationary UWB radar on the ground, is demonstrated. Finally, synthetic aperture radar (SAR) imaging using a small drone as the radar platform is explored. The entire system including a UWB radar, antennas, a camera, and a single-board computer fits on the small drone and is controlled through a Wi-Fi connection. Both the side-looking and downward-looking SAR scenarios are presented.