Design of a Wide-Band Circuit Analog Absorber Using Modified Square Loop Loaded with Lumped Resistors

In this paper, a modified square loop based circuit analog absorber with improved performance is presented. The absorber consists of a substrate with two FR4 dielectric layers separated by an air gap. On the top of the layer, a modified square loop loaded with lumped resistors is used. There is a continuous metal ground plane at the bottom layer. The proposed absorber produces three resonance frequencies in the absorption band, increasing the 10 dB reflection reduction bandwidth. It has the thickness of $0.08\lambda_{\mathrm{L}}$, where $\lambda_{\mathrm{L}}$ is a wavelength corresponding to the lowest frequency of the absorption bandwidth. It offers 10 dB absorption bandwidth of 99.24% from 3.98 GHz to 11.82 GHz which includes C band and a major part of X band, making it suitable for radar signature related applications. The simulation results show stable absorption performance for oblique incidences up to 30 degree for both the TE and TM polarized waves.