Novel tri-operational mode synthesized transmission line

A slow-wave tri-mode synthesized transmission line, showing distinct responses at three different frequencies, is proposed in this paper. The tri-mode line, consisting of a dispersive lumped-element network and two conventional microstrip sections, can be designed and analyzed using a set of synthesis equations. As a proof of concept, a synthesized microstrip line, operating as a 35-Ω 90-degree line, an open circuit, and a 50-Ω line respectively at 0.7, 1.85, and 3.55 GHz, is developed and validated. The design principle, equivalent circuit model, formulation, and experimental results are introduced and discussed.