Investigation of Bending Losses for the PTFE Dielectric Waveguide in the Sub-THz band

In this work, the bending performance of a solid cir-cular polytetrafluoroethylene (PTFE) dielectric waveguide with a 1.5 mm diameter is studied in the sub-THz band. Simulations and measurements of the 90° bending PTFE dielectric waveguides are carried out with 5/10/30 mm bending radii and the dominant HE
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mode under two orthogonal polarizations, and the investigated frequency band ranges from 88 to 140 GHz. The simulated and measured results can generally agree with each other, and the measured bending losses with a 5 mm bending radius are 0.5-7.8 dB with vertical polarized HE
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mode and 1.9-13.2 dB with hori-zontal polarized HE
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mode, respectively. In particular, the bending loss can be neglected when the radius is larger than 30 mm and the frequency is higher than 120 GHz, and adopting the polarization orthogonal to the bending direction can also decrease the bending loss. This investigation is helpful in the applications of the PTFE dielectric waveguide in the sub-THz band.