Wideband Out-of-Phase Filtering Power Divider with Ultra-Wide Isolation Band

A new design of wideband out-of-phase filtering power divider (FPD) with an ultra-wide isolation band is presented in this paper. By utilizing a vertical microstrip-slotline-microstrip (M-S-M) transition, wideband filtering performance is achieved. With a special feeding structure at input port as well as two shunted open-ended stubs at the output ports, four transmission zeros (TZs) are generated, resulting in the sharp skirt selectivity of the FPD. To well isolate the out-of-phase signals between two output ports, an isolation network consisting of grounded resistor and a microstrip line is located on the differential symmetrical plane. In addition, owing to the shunted stubs at output ports, two TZs are also generated in S
₂₃
, making the isolation bandwidth enlarged. For demonstration, generalized equivalent circuit is derived and analyzed. Finally, a prototype centered at 2.8 GHz with a 71 % of 15-dB return loss bandwidth is designed. Results indicate that the 15-dB isolation bandwidth of proposed out-of-phase FPD is up to 109 %.