A Compact Filtering Balun with Wideband and Wide Stopband Using Half-Mode SIW and Spoof Surface Plasmon Polariton

This paper presents a novel wideband filtering balun with compactness and wide stopband using the dielectriccovered F-shaped groove (DCFSG) half-mode substrate integrated waveguide and spoof surface plasmon polariton (HMSIW-SSPP) structure. Due to the DCFSG HMSIW-SSPP unit cell's dispersion curve featuring a wideband passband and low upper cut-off frequency, the proposed filtering balun has wideband properties and compact size. The proposed filtering balun is fabricated and measured. It has a wide passband (29.9% 3-dB fractional bandwidth from 6.4 to 8.65 GHz) and a wide stopband rejection (25-dB at 2.15 times the center frequency).