Fig. 1. Layout of the proposed negative coupling structure

Fig. 2. Electric-field distributions of the two coupled SIW cavities

Fig. 3. Extracted coupling coefficient and normalized inverter K/Z₀

Fig. 4. Filtering responses based on coupling matrixes

Fig. 5. Structure, simulated and measured data of the proposed filter I

Fig. 6. Structure, simulated and measured data of the proposed filter II

Fig. 7. The influence of weak dispersive cross coupling on the locations of transmission zeros