This　paper　presents　a　substrate　integrated　waveguide　(SIW)　cavity-backed　slot　antenna　for　dual-band　operation.　By　etching　a　pair　of　triangular　complementary　ring　slots　in　the　antenna＇s　back　cavity　for　radiation,　these　slots　can　effectively　excite　narrow-gap　hybrid　modes　inside　the　SIW　cavity.　One　of　the　modes　is　shifted　upward　in　the　lowest　mode　(TE120　or　TE210　mode)　and　the　other　is　shifted　downward　in　the　highest　mode　(TE320　or　TE230　mode).　The　two　modes　appear　paired　together,　which　significantly　improves　antenna　performance.　The　prototype　of　this　antenna　is　fabricated　on　a　lowcost　substrate　via　printed-circuit-board　technology.　Simulation　results　show　that　the　antenna　operates　in　two　frequency　bands　of　11.　80‒12.　50　GHz　(0.　70　GHz)　and　14.　50‒15.　00　GHz　(0.　50　GHz).　It　resonates　at　frequencies　of　12.　00　GHz　and　14.　80　GHz,　with　peak　gains　of　6.　40　dBi　and　4.　90　dBi,　respectively.　Additionally,　this　antenna　features　a　high　gain　and　a　stable　unidirectional　radiation　pattern.　©　2025　Universitat　zu　Koln.　All　rights　reserved.