Self-Packaged mm-Wave Broadband Air-Filled SIW Filtering Power Divider With Sharp Roll-Off Skirt and High In-Band Isolation

A self-packaged air-filled substrate-integrated waveguide (AFSIW) filtering power divider (FPD) operating at Ka-band with the characteristics of low loss, broadband, high in-band isolation, and sharp roll-off skirt is proposed in this letter. The filtering network is dexterously integrated into the branches of the T-junction, which is simple and compact. It is investigated in a 1-2way modified T-junction with integrated absorbers, which exhibits broadband and high in-band isolation characteristics. Cross-coupling technology is used to further improve frequency selectivity by introducing controllable transmission zeros (TZs). The prototype of FPD with a center frequency of 31.3 GHz, a $-$ 3-dB fractional bandwidth (FBW) of 16.8%, an insertion loss (IL) of 3.9 dB, a return loss (RL) of more than 18.2 dB, an in-band isolation ( $\vert S_{23}\vert)$ of not less than 17.6 dB, and an out-of-band suppression of more than 24 dB is designed, fabricated, and measured. The measured and simulated results agree well.