Ka-Band SISL-to-AFSIW Transitions With Fabrication Tolerance Characteristics

In this paper, the interconnection/transition between two popular printed circuit board (PCB) technologies, i.e., the substrate integrated suspended line (SISL) and the air-filled substrate integrated waveguide (AFSIW), is studied and designed. To obtain a smooth wave propagation and mode transition between quasi-TEM to TE10, a novel compact transition structure is proposed and investigated. In addition, the fabrication tolerance is investigated through the multilayer misalignment analysis. To experimentally validate the circuit, two Ka-band back-to-back transitions, also known as the single-layer and double-layer structures, are designed for potential multifunction applications with enhanced power handling capability and fabricated only using the low-cost FR-4 substrate. The measurements show an operation bandwidth of 26.5-40 GHz/26.5-39 GHz, the insertion loss of 0.4-1.03 dB/0.5-1.27 dB, and the return loss of better than 13 dB/12 dB of the two back-to-back transitions.