Development of Substrate Integrated Waveguides with Textile Materials by Hand-made Techniques

The substrate integrated waveguide (SIW) is an emergent technology that allows the fabrication of millimeter and microwave components and subsystems with the advantages of conventional metal waveguides, but being lighter and of easy integration of planar components and circuits . SIW is normally produced by creating rows of metallized holes using conductive cylinders or slots, which are embedded in the dielectric substrate and connect the two parallel metal plates. Some authors have presented the integration of SIW technology in new materials, such as textiles, for the fabrication of microwave components. In these works the metallized holes are made with rigid brass eyelets which already provide some flexibility, very important for further integration of the SIW components into garments. Taking this into account this paper presents the state of art about developing flexible SIW namely on textile substrates. Then, conductive materials, as for instance threads, tapes and knit strings are applied through handmade techniques to produce SIW in transmission lines. The results are then compared to transmission lines with SIW made with brass eyelet. Then, SIW antennas were also developed. All developed SIW probes were tested with a Vector Network Analyzer to measure the S11 and S21 parameters. The obtained results prove that the use of conductive threads through embroidery technique allows the implementation of more flexible SIW in textile substrates, with similar efficiency to the ones made with rigid eyelets currently in use. This technique can thus create new possibilities for the development of SIW textile antennas and components.