Design of a Compact Wideband Filtering Power Divider with Improved Isolation

A novel design of wideband filtering power divider (FPD) with high selectivity, good isolation and widen upper stopband is presented in this paper. A new topology is proposed by adding an isolation resistor between two tri-mode resonators to guarantee the isolation. Besides, owing to the intrinsic characteristics of tri-mode resonators and coupled lines with one of them terminated by an open-circuited stub, four transmission zeros (TZs) can be generated outside the operating band to improve the signal selectivity. For demonstration, a FPD operating at 2.35 GHz with 3-dB fractional bandwidth of 25.6% is designed, fabricated and measured. The measured isolation is better than 15.5 dB and the upper stopband is extended to 7.6 GHz (3.23f0) with a rejection level of 20 dB.