Compact concavo-convex cavity filters using multilayer substrate integrated waveguide

A compact bandpass filter based on concavo-convex cavity resonators is proposed. The reported resonator is developed from a conventional rectangular cavity resonator by introducing a concave surface. Compared to a conventional rectangular cavity, this new resonator has a low resonant frequency, compact size and a wider relative mono-mode bandwidth. Using the substrate integrated waveguide technique to integrate the concavo-convex cavity on a eight-layer low temperature co-fired ceramics substrate, a demonstration filter is designed, fabricated and tested to show the validity of the proposed structure.