Single-Layer Slow-Wave Substrate Integrated Waveguide with Enhanced Capacitance
In this paper, a novel slow-wave transmission line structure substrate integrated waveguide (SIW) is proposed and investigated. The slow-wave effect is achieved by the enhanced capacitance between the signal trace grid and periodic grounded patches on the same top layer. Such slow-wave effect can provide more than 40% size reduction in lateral dimension compared with the conventional SIW with the same cutoff frequency. At the same time, the longitudinal dimension can also be reduced by more than 40%. To demonstrate its applications, two-pole bandpass filters (BPF) built from conventional SIW and proposed slow-wave SIW (SW-SIW) are compared through simulations and experiments. The BPF implemented with SW-SIW reduces the size by 58.8%. Its measured unloaded quality factor (Qu) is up to 120.2.