Loss Analysis of PCB-Based mm-Wave Air-Filled Substrate Integrated Waveguides

This paper presents a detailed analysis of the determining complex propagation constants in printed circuit board (PCB) based, rectangular air-filled substrate-integrated waveguides (AFSIWs). The top and bottom layers of the proposed three-layered AFSIW enclose a high-frequency PCB material, including a milled-out air cavity and two rows of vias close to the cavity's edges. Practical design rules are extracted from this analysis, assisting RF designers to select the width of the remaining in-cavity dielectric slabs for minimal insertion loss while maintaining mechanical integrity. To validate the methods accuracy, various AFSIW samples were fabricated through a standard low-cost PCB process. Our manufactured prototypes yield an attenuation of 14.8 dB/m at 28 GHz, ensuring that the dielectric loss remains below 0.2 dB/m. The AFSIW technology paves the way for a new generation of low-profile high-performance wireless systems for the millimeter-wave (mm-Wave) satellite, communication, and radar applications.