A novel oblique-incident stable dual-band octagonal symmetric metamaterial absorber for sensing applications

Powdered food products such as milk powder, horlicks, lactogen, and coffee powder exhibit varying dielectric properties that can be leveraged for material characterization and quality monitoring. Conventional methods for analyzing such materials often involve complex, time-consuming procedures. This paper presents a novel dual-band octagonal symmetric metamaterial absorber designed to detect dielectric variations in powdered foods through high-sensitivity electromagnetic sensing. The absorber operates at resonant frequencies of 9.86 GHz and 12.50 GHz with a unit cell dimension of approximately 0.591 λ₀ × 0.591 λ₀ at the lower frequency, corresponding to an effective medium ratio of 1.69. The X-band is dedicated to powdered food sensing, while the Ku-band supports general microwave absorption applications. The structure achieves an absorption rate of up to 99.99% at both bands and maintains stable performance under oblique incidence angles up to 60°, demonstrating strong angular resilience. Numerical simulations validate the absorber's electromagnetic response and confirm close alignment with theoretical predictions. The proposed design offers a compact, sensitive, and angularly stable solution involving dielectric property detection and electromagnetic wave absorption, making it suitable for wireless and sensing technologies.