Fabricating X-Band Frequency Selective Surface on Glass Fabric by Screen Printing Method

Abstract

Frequency selective surfaces (FSSs), periodic metallic patterns on radiotransparent materials, are used to decrease radar cross section (RCS) of a radiating structure by allowing the transmittance of signals of the desired frequency band(s). A particular surface of interest is the glass fiber woven fabric which is used to manufacture polymer composite radomes. It is particularly challenging to pattern such surfaces due to inherent topography and problems regarding handling of glass fabric. This study presents modeling and manufacturing of X-band (8–12 GHz) FSS patterns on glass fabric substrate, using commercially available silver-based paste applied by the optimized screen-printing method. FSS patterns containing crossed dipole unit cells showing bandpass behavior at X-band were printed on 110 GSM (g/m2) plain weave glass fabric substrates using two different conductive pastes Type-1 (micro) and Type-2 (micro and nano) with different size distributions. Electromagnetic (EM) performances of both samples were measured using free space method and compared with each other as well as with simulation results. Experiments showed that due to the porous-like (perforated) structure of the glass fabric, accumulation characteristics of these pastes on the substrate surface are different from each other, and printed FSS layers exhibit different EM performances. As the Type-1 paste with relatively large conductive particles accumulated on the surface of the glass fabric with limited interpenetration into the fiber bundles, it acted as a continuous conductive surface which provided almost fully matching reflection and transmission characteristics with that of the simulation. In contrast, Type-2 paste with smaller conductive particles penetrated the bundles forming a partially discontinuous conductive pattern, which resulted in deviation from the expected EM behavior. Consequently, by selecting a suitable off-the-shelf conductive paste with proper characteristics for the substrate material, FSS layer with desired EM performance can be manufactured via screen-printing process without need of cumbersome surface modification.