Novel slow-wave coupled lines with coupling enhancement

A novel coupled line structure is studied based on two layers of crossing strips with dense interconnecting vias. The two arrays of vias resembling fence walls in substrate integrated waveguides help enhance the inductive coupling significantly. Dispersion characteristics of both odd and even modes are investigated with emphasis on phase equalization and impedance design as well as coupling enhancement. A specific slow-wave coupled-line structure with enhanced coupling is designed, fabricated and tested as an example. Good agreements are found between measured and simulated results of slow-wave factors, line impedances, and coupling level.