Application of vias as functional elements in microwave coupling structures

A novel application of vertical interconnects (vias) in multilayer structures, such as printed circuit boards (PCBs), is presented. By carefully designing the electromagnetic via environment, it is shown that a pair of signal vias can be used as a building block for microwave couplers. Due to the inductive nature of the coupling, the coupled port is the far end. Coupling of 0.1 dB and directivities beyond 20 dB in the frequency range from 10 to 20 GHz can be achieved. The coupling mechanisms in PCBs are investigated for different electromagnetic environments and the influence of the geometrical and material parameters on the coupler performance is explored. Results are validated by full-wave simulations and S -parameter measurements.