Design and Validation of Groundless Uni- and Bi-Directional Electromagnetic Absorbers Using Lossy Metagratings

In this article, a design methodology for groundless metagrating absorbers is proposed. By strategically arranging sub wavelength microstrip capacitors in series with chip resistors on the upper and lower layers of a dielectric substrate, uni- or bi-directional electromagnetic absorption can be effectively realized at a desired operating frequency. The entire design process is based on a fully analytical derivation, with clear mathematical theory, and is applicable across a broad range of frequencies, including microwave, millimeter-wave, and even terahertz bands. The full-wave simulation results of the proposed uni- and bi-directional absorbers show excellent agreement with theoretical calculations, validating the efficacy of the methodology. Additionally, for the bi-directional absorber, a prototype operating around 10 GHz is fabricated and measured, with experimental results aligning well with the simulated ones. Compared to other grounded metamaterial/metasurface absorbers, the proposed groundless structure offers adaptability in terms of conformability, making it more suitable for practical applications. This enhanced conformability suggests a promising potential for the future application of external electromagnetic stealth and internal electromagnetic compatibility.