A compact planar magic-T using one-third triangular resonator of substrate integrated waveguide and slotline transition

In this paper, a one-third triangular resonator with two electric walls and two magnetic walls is used as a basic transmission element to realize a planar magic-T. The resonator is fulfilled by taking out about one-third of an isosceles or equilateral triangular resonator of the substrate integrated waveguide (SIW) version and therefore, is called as one-third-mode substrate integrated resonator (OTMSIR). Due to the two virtual magnetic walls that may cause some radiation losses, the OTMSIR has a semi open structure and has a very low Q-factor, so this structure is actually a weak resonant cavity. As a result, the OTMSIR can be used to construct wide band microwave components. Different from other SIW-based ones or conventional ones fulfilled by waveguides, the magic-T proposed is realized based on the coupled-resonators technique for the first time. This planar magic-T is fabricated and tested. The measured results agree well with the simulated ones.