Athree–dimensional(3-D)broadbanddual-layermultiaperaturemicrostripdirectionalcouplerispresentedinthispaper.Thedual-layer,multiaperaturedirectionalcouplerconsistsoftwo-layerback-to-backsubstrateswith15smallcouplingaperturesonthecentergroundplane.Anovelrectangularmultiaperaturecouplingstructurew