Design of diplexer-integrated filtering power divider with high isolation

A compact size and high isolation diplexer-integrated filtering power divider (D-IFPD) is presented in this study. The proposed multifunctional circuit consists of one distributed coupling feeding line, two different stub-loaded trimode resonators, and two open-ended three-line parallel coupled lines. With the utilization of the distributed coupling technique, no additional matching circuit is needed for D-IFPD design. The measured results show that the proposed D-IFPD is centered at 1.67/2.17 GHz with 3-dB fractional bandwidths of 18.0%/12.9%, less than 0.73/1.24 dB insertion losses, better than 16.5/15 dB return losses, and higher than 35.9 dB isolation.