Substrate integrated waveguides optimized for ultrahigh-speed digital interconnects

This paper reports an experimental and computational study of substrate integrated waveguides (SIWs) optimized for use as ultrahigh-speed bandpass waveguiding digital interconnects. The novelty of this study resides in our successful design, fabrication, and testing of low-loss SIWs that achieve 100% relative bandwidths via optimal excitation of the dominant TEio mode and avoidance of the excitation of the TE₂₀ mode. Furthermore, our optimal structures maintain their 100% relative bandwidth while transmitting around 45° and 90° bends, and achieve measured crosstalk of better than -30 dB over the entire passband. We consider SIWs operating at center frequencies of 50 GHz, accommodating in principle data rates of greater than 50 Gb/s. These SIWs are 35% narrower in the transverse direction and provide a 20% larger relative bandwidth than our previously reported electromagnetic bandgap waveguiding digital interconnects. Since existing circuit-board technology permits dimensional reductions of the SIWs by yet another factor of 4:1 relative to the ones discussed here, bandpass operation at center frequencies approaching 200 GHz with data rates of 200 Gb/s are feasible. These data rates meet or exceed those expected eventually for proposed silicon photonic technologies.