Vertical Integration of Passive Microwave Components Using Functional Via Structures in LTCC Multilayer Substrates

A recently developed concept for designing passive microwave components using functional vertical interconnect accesses (vias) for vertical integration in printed circuit boards (PCBs) is extended and transferred to the low temperature cofired ceramic (LTCC) technology. Given the changed material properties and new technology constraints, it is shown how and to what extent the controlled vertical interconnect accesses (via) structures can behave as quasi-transmission lines, thus allowing for another degree of freedom in component design. To demonstrate the validity and utility of functional vias, several novel microwave components are proposed and subsequently analyzed including vertically integrated 2- and 3-way Wilkinson power dividers, as well as vertically integrated 90° and 180° hybrid couplers. Prototypes for the 2-way and 3-way power dividers were manufactured on an LTCC multilayer substrate. Both measurement and full-wave simulation results are in excellent agreement and thus provide a proof of the concept.