Fraunhofer Institute for High Frequency Physics and Radar Techniques FHRAdvanced 3D ISAR methods for imaging moving targets enable detailed capture of the spatial structure of objects in motion—even when they move quickly and complexly. In this competency area, Fraunhofer FHR develops methods that allow manned and unmanned aircraft, ground vehicles, and ships to be imaged and characterized three-dimensionally. The work aims to reflect realistic operating conditions and to provide robust, operationally usable solutions.
The focus is on moving targets captured from different perspectives: from the ground we primarily observe aircraft; from the air we image moving ground vehicles and ships at sea. Furthermore, the institute also investigates 3D imaging of aircraft from other flying platforms. In this way, the competency covers a broad spectrum of militarily relevant scenarios for moving target recognition and image characterization.
Contractual support along the entire 3D ISAR signal processing chain
Based on these efforts, Fraunhofer FHR supports industrial and military partners along the entire chain of 3D ISAR signal processing: from conception and simulation to experimental testing and prototypical implementation. Typical questions range from evaluating and optimizing existing sensor systems to developing target imaging and identification methods, up to preparing operational demonstrators in realistic scenarios.
High-resolution 3D radar echo data analysis
Technically, the work relies on high-resolution analysis of radar echoes in three dimensions. In the range direction, the target’s structure is precisely resolved via pulse propagation time measurements. A second image dimension arises from the Doppler frequency, which results from the relative motion between radar and target. The third spatial dimension is obtained through interferometric phase differences across multiple receiving channels. This yields three-dimensional point clouds or images that reveal the targets’ shape, extent, and characteristic structures.
Compressed Sensing enables precise 3D imaging
For 3D reconstruction, we employ compressed sensing methods. This allows fine target structures to be reconstructed even under limited measurement conditions—such as short observation times or restricted viewing angles—and enables efficient use of available data. Multi-channel received echoes additionally support precise estimation of target motion. This combination is especially crucial for complex flight and maneuvering movements to compensate for motion effects and generate sharp, informative 3D images.
Studies and experiments demonstrate the capabilities of 3D ISAR
The expertise in 3D ISAR is reinforced by own studies and numerous experimental projects. For example, the institute has imaged moving ships at sea in three dimensions using multi-channel radar systems mounted on aircraft. In laboratory setups, we used a Ka-band radar system to measure rotating objects in three dimensions from above on a rotation stage, thereby validating the methods under controlled conditions. Other experiments demonstrated the capabilities of our 3D ISAR approaches in the three-dimensional capture and imaging of a flying drone (quadrocopter).