Design of Two layer Frequency Selective Rasorber for Dual Band Absorption and In Band Transmission

In this paper, a frequency selective rasorber (FSR) with two absorption bands and an in-band transmission window is being proposed. The proposed structure has a two-layer geometry in which the top lossy layer consists of a circular ring having T shaped arm extensions with loaded lumped elements and a circular convoluted loop, whereas the lossless layer consists of an asterisk-based slot. The lossy and lossless layers are separated by an air spacer. The designed unit cell has a periodicity of
$0.17\lambda_{\mathrm{L}}\times 0.17\lambda_{\mathrm{L}}$
, where
$\lambda_{\mathrm{L}}$
corresponds to the wavelength of the lowest absorption frequency. The equivalent circuit modelling (ECM) concept has been used to design the FSR unit cell. The parametric analysis has been done using the Full wave simulation software. The optimized FSR design exhibits an absorptivity of more than 80% in the frequency ranges of 2.68 GHz to 6.84 GHz and 8.59 GHz to 12.89 GHz. The 3dB transmission bandwidth is in the frequency range of 7.75 GHz to 8.99 GHz with a low insertion loss of 0.29dB at 8.35GHz. The proposed structure can be used for applications that require communication as well as stealth.