Radar waves are able to penetrate through materials like cardboard or plastics and thus are able to inspect hidden objects. A 3D inspection system based on radar imaging is introduced. Opposed to X-Ray imaging, no harmful radiation is used. The system scans through the object, while it is passing on a conveyor belt. The inspection system uses a curved antenna layout, which is shown to have higher resolution than flat layouts. For processing, a custom flexible and performant algorithm is derived.