Half-Air-Filled Ball-Grid-Array-Based Substrate-Integrated Groove-Gap Waveguide and its Transition to Microstrip at W-Band

A half-air-filled substrate-integrated groove-gap waveguide is proposed for millimeter-wave and terahertz applications. The waveguide is constructed by a ball grid array using a flip-chip technique without metallic vias with lightweight and low profile. The possible leakage perpendicular to the groove is prevented by solder balls as modeled by an equivalent circuit. Besides, an inline transition between the proposed waveguide and a microstrip line is proposed, fabricated, and measured. The design concept and working mechanism are explained. Good agreement between simulation and measurement is observed. The simulation shows that the proposed waveguide can cover the entire ${W}$ -band (70–118 GHz), and the measurement demonstrates that the proposed transition can operate at 90–98.8 GHz.