All-PCB transmission line with low loss and dispersion up to Ka band

A novel approach for constructing a low-cost transmission line by stacking machined printed circuit boards (PCBs) is proposed. The line mimics the fully enclosed rectangular coaxial line with over 75% air and, therefore, demonstrates a low-loss and low-dispersion performance. The approach is employed to design and fabricate a transmission line operating up to the Ka band with only 0.15 dB/cm maximum measured insertion loss at 40 GHz. This study demonstrates the suitability of the stacked PCBs for realization of wideband 3D transmission lines for centimeter-wave and millimeter-wave applications with much lower cost than the available microfabrication processes.