Design of A Ultra- Wideband Absorber in the UHF Band

In this paper, a UWB absorber in the UHF band is proposed. The structure of the absorber is manly consisted by two absorbing layers. For the upper layer, resistive film is periodically printed on the FR-4 substrate. For the lower layer, a metal ring loaded with lumped resistances is attached to the same dielectric substrate, which extend the absorbing band to lower frequency. The size of unit is 50mm× 50mm× 67mm(0.072?_max) and the simulated results illustrate that the absorber can achieve more than 90% absorption rate from 0.32GHz-1.13GHz with a 111.7% fractional bandwidth under normal incidence. Meanwhile, the absorber maintains good absorptance within the range of 30°at oblique incidence.