G-Band Mode-Coupler-Based Si Dielectric Waveguide for Multidrop Sub-THz Interconnect

This letter presents a G-band mode-coupler-based multimode Si dielectric waveguide (DWG) for multidrop sub-THz/THz interconnect. Three types of mode couplers, i.e., quasi-transverse electromagnetic (TEM) to $E_{11}^{y}$ mode, $E_{11}^{y}$ to $E_{21}^{y}$ mode, and $E_{11}^{y}$ to $E_{31}^{y}$ mode, are designed and demonstrated. The quasi-TEM to $E_{11}^{y}$ coupler works as microstrip line (MSL)-to-DWG transition. $E_{11}^{y}$ to $E_{21}^{y}$ and $E_{11}^{y}$ to $E_{31}^{y}$ mode couplers enable two more mode transmissions along the bus waveguide through the dedicated couplers where the phase match condition is satisfied. Tapers are used as the smooth transition between DWG sections, as well as mode filters to reduce the crosstalk between modes in (de)multiplexers. The measured minimum transition loss is about 5 dB with the 3-dB bandwidth of 143–200, 151–185, and 155–174 GHz for the three modes, respectively, and the measured crosstalk between modes is less than −26 dB.