Design of Out-of-Phase Filtering Power Divider Based on Slotline and Microstrip Resonator

A new design of filtering power divider (FPD) with a pair of highly isolated out-of-phase outputs is presented. By combining the conventional slotline-microstrip transition with microstrip resonators, the proposed FPD is initially constructed. Owing to the field conversion from the slotline to the microstrip line, two signals with equal magnitude and 180° phase difference are simultaneously obtained at two output ports. Specifically, to isolate two output ports, a new isolation network composed of a microstrip line and a grounded resistor is loaded on the differential symmetrical plane. By adopting the even-/odd-mode analysis method, the working principles for both of filtering and isolation are explained with design equations. For demonstration, two prototypes of out-of-phase FPDs operating at 3.4 GHz with 3-dB fractional bandwidths of 8% and 18% are designed, fabricated and tested, respectively. Simulated and measured results are displayed to verify the theoretical design equations.