“…However, the unload quality factors (Q u ) of SIW cavities are deteriorated by the special slot lines, which results in large in-band insertion loss (IL). The second one is using the incomplete mode SIW cavities, e.g., half-mode SIW (HMSIW) [13,14,15,16,17], quarter-mode SIW (QMSIW) [18,19,20,21,22,23], and eighth-mode SIW (EMSIW) cavities [19,22,23,24]. The sizes of them can be reduced, especially in the EMSIW cavity.…”