Design of A Novel Wideband Microwave Absorber with High Absorptance

In this paper, a wideband microwave absorber with high absorptance based on double layer structure is proposed. Two similar metal rings loaded with resistances are attached to the upper and lower surfaces of the dielectric substrate. Its bandwidth is mainly determined by the two high resonant points of lower layer and two low resonant points of upper layer. The size of unit is 40mm$\times$ 40mm$\times$ 11mm. The simulated results show that the absorber can achieve more than 95% absorption rate from 2.67GHz-6.88GHz under normal incidence, the fractional bandwidth is 88.1% and the band-in average absorption rate is 97.1%. The total thickness is only 0.097$\lambda_{L}$, where $\lambda_{L}$ is the wavelength at 2.67GHz. Meanwhile, the absorber maintains good absorptance within the range of 40° at oblique incidence.