Abstract
This paper considers the four most common equivalent network models of a single-layer circuit-analog absorber, and demonstrates that the series RLC configuration performs superior to the others. With proper selection of the component values, this configuration can realize two resonances, which lead to an overall wideband absorption. Based on this finding, we derive closed-form design expressions for an optimally thin and wideband single-layer absorber. To demonstrate the superiority of the series RLC absorber, a design example has been provided where 10-dB bandwidth of 128% is obtained through a single-layer absorber whose thickness is less than lambda/11 at the lowest frequency of absorption.