Non-invasive microwave imaging for metallic contaminant detection in packaged peanut butter

This paper presents a simple, fast, and non-invasive microwave imaging (MWI) approach for the detection of metal foreign objects embedded within commercially packaged peanut butter jars. The proposed MWI system consists of ten ultrawide-bandwidth (UWB) coplanar Vivaldi antennas arranged in a circular array operating over a frequency range of 3.32–8.71 GHz, a vector network analyzer for acquiring scattering parameters, an automatic high-speed switching system, and a computer. The scattering parameters are subsequently used to reconstruct microwave images of metallic inclusions. Experimental validation was performed on a commercial peanut butter jar, demonstrating that the system can reliably detect metallic foreign objects with diameters as small as 1 cm while providing accurate localization and size estimation. Furthermore, the proposed approach successfully identified the simultaneous presence of multiple metallic objects within the packaged product. These results indicate that MWI is a promising non-destructive technique for real-time foreign object detection in packaged peanut butter inspection.