A Novel Switchable Absorber/Reflector Based on Diode-embedded Square-loop Array

The switchable absorber/reflector with diode-embedded square-loop array is designed for radar cross section (RCS) of target. The proposed structure consists of a top switchable layer, an air spacer, and a bottom metal ground. As the core component, the top layer contains the square-loop array connected by four metallic strips. Total eight p-i-n diodes are soldered in the outer square-loop to switch wideband absorption or high-efficiency reflection, and four lumped resistors are loaded into the metallic strips to consume external wave energy. In addition, by using these metal strips, the p-i-n diodes can be driven without additional bias lines, thus reducing the influence of bias network on the electromagnetic characteristics of the proposed structure. When all p-i-n diodes are turned ON, the parallel resonance provided by the ON-state dual square-loops can generate a narrowband transmission window. And the background reflects the incident wave, resulting in a high-efficiency reflection at 4.92 GHz with 0.5 dB return loss. By flipping the working state of p-i-n diodes, the outer square-loop is divided into many small segmentations by OFF-state p-i-n diodes, so the entire structure is viewed as a circuit analog absorber with −10 dB bandwidth ranging from 3.2 GHz to 7.0 GHz (corresponding to a fractional bandwidth of 74.5%). Compared with previous switchable absorber/reflector designs, the proposed integrated structure can not only realize wideband absorption, but also achieve high-efficiency reflection in the absorption band.