Compact Multilayer Half Mode Substrate Integrated Waveguide 3-dB Coupler

In this letter, a wideband compact 3-dB coupler is designed based on the multilayer half mode substrate integrated waveguide (HMSIW) theory and Bethe hole coupling theory. The design utilizes higher band of quasi-TE
_0.5,0
mode in HMSIW and dual-layer structure to reduce the size of component. This letter also theoretically proposes a relationship between SIW and HMSIW broad wall coupler with the same coupling section, which can obviously simplify the design procedure and maintain stable coupling differences. Meanwhile, this coupler shows a 3-dB coupling over a wide bandwidth with a single row of only five small apertures, which needs more in SIW and waveguide circuits. In long term, the method of cutting SIW components along magnetic wall to get HMSIW components can also play an important role in the future design, especially in size reduction and performance improvement of the circuits. Simulation results are in agreement with the measured data.