Half-mode substrate integrated plasmonic waveguide for filter and diplexer designs

A half-mode substrate integrated waveguide (HMSIW) combined with spoof surface plasmon polariton (SSPP) structure is proposed to realize bandpass filter (BPF) characteristic and miniaturization, which is termed as the half-mode substrate integrated plasmonic waveguide (HMSIPW). Compared with the conventional HMSIW structure having identical cutoff frequency, this new design of HMSIPW not only supports SSPP modes, but also realizes a transversal size reduction of 19.4% and longitudinal reduction of more than 60%. Then, a diplexer based on two back-to-back placed HMSIPW BPFs is designed, and it has only one row of metallized via holes to further reduce the transversal size. The experimental prototypes of the filters and diplexer have been manufactured, and the measurement results agree well with simulation ones. Due to the size miniaturization and simple structure, the proposed designs will have many potentials in the integrated devices and circuits for wireless communication systems.