Miniaturised frequency selective surface‐based rasorber with wideband two‐sided absorption and switchable transmission/reflection band

A new rasorber with a switchable transmission/reflection band between two wide absorption bands is proposed based on an ultrathin low-profile frequency selective surface. To miniaturise the periodicity in the lossy layer, convoluted elements and lumped capacitors are applied, while in the bandpass layer, non-resonate elements are implemented with PIN diodes embedded. Moreover, a square loop loaded with resistors is introduced to the bottom of the lossy layer, which consequently extends the bandwidth of the high-frequency absorption band without an increase in thickness. The simulation indicates that the proposed design presents a switchable transmission/reflection band in two-sided absorption bands with a periodicity of 0.089 lambda(L) (wavelength at the lowest operating frequency) and thickness of 0.066 lambda(L). Angular stability and polarisation insensitivity are also obtained due to the low profile and symmetry. A prototype was fabricated and measured, according to which the switchable transmission band covers 3.67-3.93 GHz; the absorption bands cover 2.37-3.23 GHz and 4.09-6.63 GHz in the OFF state of the diodes, and 2.23-3.02 GHz and 4.01-6.53 GHz in the ON state. As reasonable agreements between the measurement and simulation results are observed, the performance of the design is verified.