Balanced Dual-band SIW Bandpass Filter With Enhanced Selectivity

The contribution of this work is to propose a novel substrate integrated waveguide (SIW) dual-band balanced bandpass filter (BPF) with enhanced selectivity. In order to achieve this aim, both source-to-load and cross-couplings are employed by implementing four resonant nodes in two cavities, for the purpose of generating one pair of additional transmission zeros (TZs). Within this design, TE
₁₀₂
and TE
₂₀₁
are two dominant modes inside each cavity and each correlates with one passband responses. Due to their symmetric field distributions, balanced inputs/outputs can be assigned. The center frequencies of two passbands can be easily tuned by changing dimensions of cavities, while out-of-band skirt are tuned by changing dimensions of coupling slots. A second-order prototype is designed and fabricated for the demonstration. A good agreement is obtained between simulated and measured results.