Design of substrate integrated magic-T based on hard-soft EBG materials

This study presents an innovative substrate-integrated magic-T design incorporating multilayer soft-and-hard electromagnetic bandgap (EBG) structures, which effectively overcomes the electromagnetic compatibility limitations associated with slot-coupled configurations in conventional single-layer substrate-integrated magic-T devices. The proposed design features a groundbreaking integration of soft and hard surfaces within the substrate architecture, simultaneously addressing interlayer contact reliability challenges in multilayer implementations while achieving a fully-enclosed structure with performance characteristics comparable to waveguide magic-T components. Experimental validation at Ka-band demonstrates excellent performance metrics: better than 15 dB return loss across all ports, typical insertion loss of 4.2 dB for both sum and difference ports, with phase characteristics showing 2.3°~4.7° imbalance for the sum port and 184.1°~187.4° deviation for the difference port. The compact design achieves significant size reduction over conventional waveguide magic-T structures while maintaining superior electrical performance, offering an advanced solution for spaceborne antenna beamforming systems requiring compact sum-and-difference networks.