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

The satisfactory realization of a metamaterial (MM) absorber simultaneously occupying low-profile, wide-bandwidth, particularly and fully angular stability characteristics is a long-term challenge. In this article, we propose a new design method to accomplish above realization based on the 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 the TM-polarized wave. In order to guide our design, the characteristic mode theory is first employed to synthesize the omnidirectional 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 $0.11\lambda _{0}$ 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 be, respectively, up to incident angles of 82° and 45°, and its effectiveness within 10°–70° is verified with measurements.