Broadband Filtering Power Divider Employing Hybrid Quarter Circular/Cambered SIW Cavity and MSL Resonators

In this letter, a broadband filtering power divider (FPD) based on a quarter circular/cambered substrate integrated waveguide (QCCSIW) cavity and microstrip line (MSL) resonators is proposed. First, a second-order bandpass filter (BPF) is designed based on the arc-shaped coupling of the QCCSIW. Second, a pair of quarter-wavelength ( $\lambda $ /4) MSL resonators are integrated into the QCCSIW cavity to form a fourth-order asymmetric BPF with a pair of transmission zeros (TZs). Finally, a hybrid QCCSIW and MSL FPD with isolation is investigated. For verification, all BPFs and FPD are simulated, fabricated, and measured. The proposed FPD demonstrates a center frequency of 4.99 GHz, a 3-dB fractional bandwidth (FBW) of 37.11% (1.85 GHz), and an insertion loss (IL) of 0.8 dB. The port isolation is greater than 11 dB within the entire passband. Meanwhile, a pair of TZs are generated at 3.62 and 6.35 GHz respectively. The proposed hybrid QCCSIW and MSL FPD possesses an overall size of $1.73\times 1.74~\lambda _{g}$ , featuring advantages of broad bandwidth, compact size, and superior selectivity.