RF Balanced-to-Single-Ended Out-of-Phase/3-dB Filtering Power Divider With Differential-Mode Input-Quasi-Reflectionless Behavior

A novel class of balanced-to-single-ended (BTSE) out-of-phase/3-dB power divider with added high-selectivity filtering and RF-input-quasi-absorptive capabilities is reported. This type of RF multifunctional power-division/filtering component consists of a planar/single-layer mixed-mode magic-T on microstrip-to-slotline transition with a resistively-terminated multistage transmission-line section loaded at its $\Sigma$ port, along with two reflective-type quadruplet-based bandpass-filter (BPF) units and phase-delay stages at its arms. In this manner, the fourth-order sharp-rejection filtering transfer function with two transmission zeros (TZs) of the embedded quadruplet BPF unit is co-integrated along with the RF power-splitting function. Furthermore, owing to the transversal cancellation at the input access between the out-of-band RF signals reflected by both the branches after the action of the phase-delay stage at the input of one arm, a differential-mode (DM) RF-input-quasi-absorptive behavior is obtained. The basic theoretical foundations and equivalent circuit model of the devised DM-input-quasi-reflectionless BTSE filtering power divider are shown. Furthermore, for practical validation purposes, a 3-GHz proof-of-concept prototype is built and tested.