Polarization Insensitive Metamaterial Absorber Operating at a Single Band for 5G and Advanced Sensing Technologies

This work presents a polarization-insensitive high Q metamaterial absorber operating at the 3.5 GHz 5 G band for ultra-sensitive material sensing. The proposed absorber is based on a compact single layer unit cell with a multi grooved square ring resonator and is fabricated on a low-cost FR-4 substrate. The structure exhibits a normalized electrical size of 0.12λ × 0.12λ × 0.018λ. At resonance, near unity absorption of 99.02% is achieved, while stable performance is maintained for both TE and TM polarizations under oblique incidence angles up to 80°. The absorber is designed to provide strong absorption along with a sharp resonance and a high Q-factor, which is essential for sensing applications at sub 6 GHz frequencies. For solid material sensing, the structure achieves a sensitivity of 13.828 with a quality factor of 304.348 and a figure of merit of 3923.515. In the case of oil sensing, a sensitivity of 13.371 with a quality factor of 323.511 and a figure of merit of 3734.241 is obtained. These results exceed many previously reported metamaterial absorber-based sensors operating in similar frequency ranges. The absorption mechanism is explained using surface current distributions, electromagnetic field analysis, impedance matching, and an equivalent circuit model, while the sensing behavior is attributed to resonance frequency shifts caused by variations in the permittivity of the material under test. The absorption performance is experimentally verified by fabricating and measuring a 100 × 100 mm 2 prototype array, which exhibits close agreement with simulation results. The proposed MMA offers a compact, robust, and practical solution for 5 G enabled sensing applications.