A Polarization-Insensitive Broadband Metamaterial Absorber with Controllable Absorption Intensity

The work presents a wideband, polarization-insensitive, and dynamically tunable metamaterial absorber. The absorber is constructed with a simple design consisting of a top layer circular array loaded with four PIN diodes, a middle dielectric substrate, and a bottom metal layer. Simulation results illustrate that by adjusting the bias voltage applied to the PIN diodes, the absorber can dynamically tune from near-total reflection to below −13 dB over a broad frequency range spanning from 4 to 12 GHz. Additionally, the absorber maintains its polarization insensitivity due to its symmetric structure. An accurate equivalent circuit is developed to explain the underlying physical mechanism of the absorber, and the absorption peaks are analyzed by examining the electric field distribution. Experimental samples of the absorber are fabricated and tested, demonstrating close agreement with the simulation results.