Wideband circuits designed on one-third equilateral triangular cavity

In this paper, a one-third triangular resonator with two electric walls and two magnetic walls is discussed as a basic resonant element to realize wideband passive circuits. 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. Therefore this structure is actually a weak resonant cavity. As a result, the OTMSIR can be used to construct wideband microwave components. Moreover, some transmission version components, for example, Magic-T can also be realized based on the OTMSIR. Different from other SIW-based ones or conventional ones fulfilled by waveguides, these transmission version microwave components proposed are realized based on the coupled-resonators technique.