Polarization Independent Super Thin Metamaterial Microwave Broadband Absorber for X-Band Application

In this paper polarization independent super thin metamaterial microwave broadband absorber for X-band application has been reported. The presented unit cell absorber is comprised with four chip resistor (lumped element) which are connected with the close ring resonator (CRR) and Inside the CRR the circular resonator is incorporated to improve the bandwidth of the absorber. The top metallic patch is printed on the super thin FR4 epoxy $((\varepsilon_{\mathrm{r}}=4.4),\ (\tan(\delta)=0.02))$ substrate having $\mathrm{t}\mathrm{h}\mathrm{i}\mathrm{c}\mathrm{k}\mathrm{n}\mathrm{e}\mathrm{s}\mathrm{s} (0.07\mathrm{m}\mathrm{m})$ with air spacer. The absorption of bandwidth is given by the presented unit cell is above the 90% in the frequency band of 6.3 GHz to 12 GHz. The unit cell is symmetrical in nature so it is given the same absorption at the different polarizations angles up to $90^{\mathrm{o}}$, thus shows polarization-insensitivity behavior. The response is stable for an oblique incident angle for both TE and TM mode up to $45^{\mathrm{o}}$ and with further increase in angles the absorption reduces significantly. The surface current distribution for absorption frequency are analyzed to study the absorption mechanism.