Crosstalk Suppression by Shielding in Dielectric Waveguide Interconnect Arrays

To obtain a high data rate density (Gb/s/mm) in arrays of mm-wave dielectric waveguide (DWG) interconnects, the interconnect pitch must be small. Unfortunately, small pitch results in significant field coupling, hence crosstalk, between adjacent waveguides. To quantify the effect of coupling on interconnect density, we first determine crosstalk between two parallel unshielded DWGs and calculate the minimum pitch required for acceptable crosstalk (−30 dB) in 1–10 m links. We find that DWGs using alumina cores, with expanded PTFE (e-PTFE) cladding, can tolerate smaller pitch at a given crosstalk than DWGs using PTFE cores. Then we analyze a DWG design where a metallic shield surrounding the e-PTFE cladding suppresses crosstalk; with appropriate cladding size, this shield only negligibly increases DWG attenuation. Constraining crosstalk to −30 dB, for a 10 m link, the shielded designs provide 14:1 greater interconnect density (guides/mm2) for PTFE-core DWGs and 8:1 greater interconnect density for alumina-core DWGs.