Near field food contamination detection technique employing a compact Antipodal Vivaldi antenna

This paper presents a simple yet robust technique for identification of the presence of contaminants in food samples by detecting the variation in the transmission coefficient ($S_{21}$) in a near field measurement setup. A compact step-notched antipodal Vivaldi antenna with a frequency range of operation 3 $-$ 18 GHz, and realized gain of 12.81 dB at 16 GHz having compact dimensions $60mm\times 40mm\times 0.51mm$, i.e., $0.6\times 0.4\times 0.005{\lambda }_0^3$ (where ${\lambda }_0$ is the free space wavelength at the lowest frequency of operation) is designed for contamination detection due to its compact size, high directivity and high boresight gain for near-field measurement. An equivalent image is constructed from the S $-$ parameters, measured at different positions and different antenna polarizations over the frequency range of 3-18 GHz for metallic contaminants, i.e., iron ball and aluminum foil. An algorithm is developed for detection of contamination from the images using the reference case of no-contamination scenario. The proposed algorithm is validated using full-wave simulation.