Synthesis and Measurement of DBE Exceptional Points in Substrate-Integrated Waveguides

International audienceThis paper proposes a method to engineer degenerate band-edge conditions in periodic substrate-integrated waveguides (SIWs). A degenerate band edge is a fourth-order exceptional point originating from the coupling of four Floquet-Bloch modes; it leads to a dispersion relation flatter than a regular band edge and is suitable to design slow-wave structures and high Q-factor resonators. Design guidelines to achieve a degenerate band edge point are given based on Bloch analyses of unit cells. An oblique line of vias in SIW is proposed to form a suitable modal coupling between adjacent waveguides enabling a degenerate band-edge condition. The effect of losses and the robustness to parameter variations are discussed by means of rigorous Bloch analyses. A unit cell showing the best behavior concerning the losses and geometric tolerances is selected and prototypes of finite-length resonators are realized. Measurements validate simulated results and confirm the typical N 5 scaling of the loaded Q factor to the number of cells N of the resonator