An improved coplanar waveguide to slotline transition for multi-layer circuit structures

A novel transition from coplanar waveguide (CPW) to slotline is presented in this paper, which utilizes conduct vias and metal strips to connect two ground planes of CPW instead of air bridges. The metal strips which connect the two ground planes in the back of CPW are used to suppress the reflected slotline mode in order to reduce the return loss and enlarge the bandwidth. The CPW stub used as a phase shifter converts the CPW mode to slotline mode. Due to the absence of the air bridges in the component structure, the transition can be integrated on a multilayered microwave and millimeter-wave circuits. Compared to other transitions, the proposed transition has the advantages of higher compactness, simpler fabrication, lower radiation and lower cost. The simulation results and measurement data have verified the proposed transition.