A Fully Polarimetric Radar System for Non-Destructive Testing of Fiber Glass Layers

During the production of fiber composites, individual layers can be displaced, which can drastically influence the load-bearing capacity of the object to be manufactured. Existing systems in the field of non-destructive testing of fiber composites are either impractical to use in everyday production or do not offer the possibility of examining the structure of the individual fiber layers. For this reason, we present a novel sensor concept that can detect typical defects caused during manufacturing. The concept is based on a millimeter wave SAR approach using a fully polarimetric FMCW radar sensor working at a center frequency of 60.5 GHz, with 17 GHz bandwidth. The sensor offers a phase noise of -77 dBc/Hz at 1 MHz offset from the carrier, with chirp times of 1 ms over the whole bandwidth, while maintaining a RMS frequency deviation of 1.24 ppm. Using a polarimetric decomposition scheme, we can detect the displacement of individual fiber layers, although the thickness of the layers is below the theoretically achievable range resolution of the radar.