A free-space dielectric system with X-band coaxial-to-waveguide adapters for nondestructive fertility detection in unincubated chicken eggs: Optimizing spectrum, orientation, features, and classifiers

Detecting infertile eggs before incubation can significantly improve hatch rates and reduce losses associated with billions of infertile eggs. This study employed a free-space dielectric setup with X-band coaxial-to-waveguide adapters to assess egg fertility prior to incubation. Scattering parameters within the 8–12 GHz microwave spectrum were analyzed in both reflectance and transmittance modes, with eggs examined in two distinct orientations. Each sample orientation generated eight spectra, which were preprocessed using various techniques. Seven classifiers were applied to differentiate fertile from infertile eggs, resulting in 576 classification models aimed at identifying the optimal spectrum, sample orientation, preprocessing method, and classifier for distinguishing unincubated fertile and infertile eggs. The insertion loss spectrum in S₂₁ mode (IL_S₂₁) in the vertical orientation was identified as the optimal condition. Several feature selection methods were then evaluated to determine the most informative frequencies. Predictive models were developed using artificial neural networks (ANN), random forest (RF), and boosted trees (BT), leveraging the selected effective frequencies. Notably, the competitive adaptive reweighted sampling (CARS) approach consistently outperformed other methods, yielding robust BT models with an exceptional F1-score of 100 %. In the BT model, CART-based features achieved a sensitivity of 96.00 %, specificity of 93.55 %, precision of 92.31 %, accuracy of 94.64 %, and an F1-score of 94.12 %, comparable to the BT model based on full spectral data (F1-score of 98.04 %). A trade-off exists between the higher accuracy of CARS-selected features and the more localized frequency selection in the CART-based approach. This study highlights the effectiveness of free-space dielectric setups in reliably distinguishing fertile from infertile eggs prior to incubation, offering substantial implications for the poultry industry.