Study Examines How Printed Circuit Boards Affect Terahertz Waveguide Performance in Compact Electronics
Researchers have experimentally and numerically demonstrated that placing 3D-printed polypropylene dielectric waveguides near printed circuit board (PCB) substrates induces measurable excess transmission loss at terahertz frequencies (220–325 GHz). The study tested bare FR4, fully copper-clad, and periodic copper-trace PCB configurations at varying clearances, finding that direct contact with bare FR4 creates a frequency-selective high-loss band due to phase-matched leakage into a substrate-supported leaky mode. The findings provide practical design guidance for clearance control and metallization strategies in compact terahertz interconnect packaging.
As demand grows for high-capacity, low-loss short-reach data links in densely integrated electronic systems, terahertz (THz) dielectric waveguides have emerged as promising interconnect channels. However, because these air-clad waveguides have evanescent fields extending beyond their physical boundaries, nearby PCB structures can interfere with signal transmission. This study by Jianjun Ma and colleagues, submitted to Nano Communication Networks, used continuous-wave THz measurements and terahertz time-domain spectroscopy to characterize how three PCB configurations — bare FR4, continuous copper-clad, and periodic copper-trace — affect transmission in 3D-printed polypropylene rectangular waveguides. The key finding is that bare FR4 in direct contact with the waveguide produces a frequency-selective high-loss band, attributed to phase-matched coupling of the guided mode into a leaky branch supported by the substrate. Copper metallization on the PCB surface was found to alter this interaction, offering a potential mitigation strategy. The results establish PCB proximity as a critical layout parameter that must be carefully managed in compact THz system-in-package designs. The work provides quantitative guidance on minimum clearance distances and metallization choices to minimize proximity-induced losses.
What's missing
The paper has not yet completed peer review, as it is a preprint submitted to Nano Communication Networks. Long-term reliability and fabrication tolerance of the 3D-printed polypropylene waveguides under realistic thermal and mechanical PCB assembly conditions are not addressed.
What different sources said
- arXiv physicsCenter
Near-Field Coupling of Polypropylene Dielectric Waveguide Routed Near PCB Board at Terahertz Frequencies
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