Coupling analysis of polytetrafluoroethylene dielectric waveguides in the sub-THz band

This letter investigates the coupling between two parallel-placed polytetrafluoroethylene (PTFE) dielectric waveguides over the frequency band from 90 to 110 GHz. The coupling is considered under different working frequencies, coupling spacings, coupling lengths, and polarizations. Simulations and measurements are carried out, and the results indicate the coupling can be significantly reduced by increasing the operating frequency and coupling spacing and adopting vertical polarization (VP) for a specific coupling length. In particular, the simulated and measured results with a 9-mm coupling distance under two polarization states can be kept under -30 dB for 50- and 100-mm coupling lengths, leading to negligible interference. In the practical arrangement of PTFE dielectric waveguides working at the other frequencies, one can follow the same rule to reduce the coupling between waveguides and thus avoid interference.