A Low-Profile Ultra-Wideband Absorber Using Lumped Resistor-Loaded Cross Dipoles With Resonant Nodes

This article presents the design and analysis of a dual-polarized low-profile circuit analog absorber with wideband absorption characteristics. A lossy frequency selective surface consisting of cross dipole with central resonant node element is used as the top layer, while there is a continuous copper ground as the bottom layer. The novelty of the design lies in the use of the resonant node as it improves the absorption bandwidth by providing an additional resonance without compromising the low-profile nature of the design. It has a thickness of 0.077
$\lambda_{L}$
(where
$\lambda {\_}L$
is the wavelength corresponding to the lowest operating frequency). The absorber also exhibits a stable absorption characteristics up to 30
$^\circ$
angle of incidence and can avoid grating lobes within the operating bandwidth up to 40.79
$^\circ$
angle of incidence. An equivalent circuit model is proposed to discuss the operating principles of the design. The validation of the design is done experimentally using the time-gating technique, and a good agreement between the measured and the simulated results is observed. The 10-dB reflection reduction bandwidth and the thickness-to-bandwidth ratio of the absorber are obtained as 108.67% (from 3.58 to 12.10 GHz) and 0.104 from full-wave simulation and 115.67% (from 3.5 to 13 GHz) and 0.098 from measurement, respectively.