Flexible Convoluted Ring Shaped FSS for X-Band Screening Application

A flexible and low profile frequency selective surface (FSS) with bandstop behavior for $X$ -band signals is demonstrated in this paper to support the demand of the flexible wireless communication devices in the today’s market. The resonating element of the FSS is realized using the convoluted ring loop element that is inspired by the conventional ring loop element. An additional of four stubs are added at each 90° of the conventional ring loop to miniaturize its overall dimension. The convoluted ring loop FSS has reduced the overall dimension of the conventional ring shape FSS to 0.25 $\lambda _{0}$ with a reduction of 33%. The proposed FSS is developing by utilizing the flexible polyethylene terephthalate substrate with the measured thickness of 0.125 mm and dielectric constant of 2.7. From the simulated transmission response of the FSS, it shows that the proposed convoluted ring loop FSS with planar feature manages to provide a signal attenuation up to 37 dB at 10 GHz for both normal and oblique angle of incidence up to 45° at TE and TM polarization. For validation purpose, the prototype of the FSS is manufactured using the inkjet printing technique. The FSS is bent in a different manner, such as bending the array FSS with different radius and bending the unit cell convoluted ring FSS row by row, to examine the bending effect toward the transmission response performance. All the simulated results are compared with the measured results, and these results are in concurrence with each other. By having the conformal features, the employability of the FSS is enhanced whereby the proposed flexible FSS can be employed as the sub-reflector for wearable antenna and conformal shields for electromagnetic compatibility applications.