Filtering power divider with high selectivity using modified coupled-line bandpass filter

This letter presents a filtering power divider using modified parallel coupled-line bandpass filter (BPF) with multiple coupling from source/load to resonators. This novel coupling topology includes additional coupling between source/load and non-adjacent resonators, namely, extra cross-coupling paths, for a better selectivity. Then less resonators are required to achieve the same stopband performance compared with conventional parallel coupled-line BPF with the same order. Three isolation resistors, instead of only one in the conventional power dividers, are used for flexible optimization of isolation. For validation, a three-order filtering power divider operating at 3.4 GHz is demonstrated with more than 14 dB in-band isolation. Three transmission zeros are generated at 2.02 GHz, 2.56 GHz and 4.34 GHz to achieve a better selectivity.