Terahertz Channel Transmission in Dielectric Waveguide Near PCB Substrate

TL;DR

This study investigates terahertz dielectric waveguide transmission near PCB substrates, revealing how proximity and PCB composition affect signal loss, and offers insights for designing packaging-aware THz interconnects.

Contribution

It provides experimental and simulation analysis of THz waveguide behavior near PCB substrates, highlighting the impact of PCB materials and separation on signal attenuation.

Findings

Bare PCB contact causes severe frequency-selective loss.

Copper layers suppress substrate leakage and reduce loss.

Increasing separation decreases excess attenuation.

Abstract

The growing demand for high-capacity, low-loss short-reach links in highly integrated electronic systems makes it necessary to understand how terahertz (THz) dielectric waveguides behave in realistic PCB-level packaging environments. In this article, we investigate the channel transmission of a 3D-printed polypropylene dielectric waveguide placed near representative PCB substrates. Continuous-wave THz measurements are carried out for bare, fully copper-clad, and periodic copper-trace PCBs with different waveguide-PCB separations, while terahertz time-domain spectroscopy is used to characterize the dielectric properties of the substrate materials. In parallel, an equivalent radiation-channel model and simulations are employed to interpret the proximity-induced excess attenuation. Most notably, direct contact with a bare PCB produces severe and frequency-selective excess loss, whereas a waveguide-facing copper layer suppresses substrate-assisted leakage and reduces the excess loss, with the attenuation rapidly decreasing as the clearance increases. These results reveal the dominant near-field coupling mechanisms between dielectric waveguides and nearby PCB structures, and provide practical guidance for packaging-aware THz interconnect design.