Quantifying the impact of seam compression on embroidered textile substrate-integrated structures

Embroidered textile electromagnetic structures based on substrate-integrated technology use computer-controlled stitching with metalized yarns to form metallic side walls. In these structures, the tensile stress of the thread compresses the flexible substrate along the seams. As a consequence, the overall shape of a manufactured design is modified, which will both impact the frequency and efficiency of the structure. In this paper, the mechanical impact of the seam compression on manufactured antennas is first estimated for two types of low-permittivity substrates, namely closed foam and felt material. Then, the influence of the depth and width of the compression is quantified in terms of electromagnetic performance for a textile half-mode substrate-integrated cavity antenna, a substrate-integrated waveguide and a shielded stripline. It is demonstrated that seam compression significantly improves the efficiency of this type of structures, but comes at a cost of of slightly increased overall dimensions.