Near-Omnidirectional Broadband Metamaterial Absorber for TM-Polarized Wave Based on Radiation Pattern Synthesis

The satisfactory realization of metamaterial (MM) absorber simultaneously occupying low profile, wide bandwidth, particularly and fully angular stability characteristics is a long-term challenge. In this paper, we propose a new design method to accomplish above realization based on radiation pattern synthesis. In the design, a mushroom-type MM absorber is simply covered with different resistive sheets, which empower it with the admirable low profile, wide bandwidth, and near-omnidirectional absorption for TM polarized wave. In order to guide our design, the characteristic mode theory is first employed to synthesize omni-directional radiation pattern and the dissipation tailoring is then utilized to achieve the impedance matching and near-omnidirectional absorption conversion. A proof-of-concept sample is fabricated and measured for verification. At quasi-normal incidence, the measured bandwidth characterized by absorption more than 90% covers 1.5-4.5 GHz with fractional bandwidth (FBW) 100% and the thickness about 0.11λ0 at 1.5 GHz. In the frequency band of 1.9–4.2 GHz, the simulation results indicate that the absorption for TM and TE polarizations of approximately 90% can respectively up to incident angles of 82° and 45°, and its effectiveness within 100-700 is verified with measurements.