Multi-port Filtering Power Dividing Networks

Multi-port filtering power dividing networks have been applied widely in modern communication systems due to their high integration level by fusing filtering function and power dividing function into one component. The reported filtering power dividing networks are realized by using filters cascading to power dividing network or using the two identical filtering structures symmetrically coupled to one input feed line, which always suffer from large circuit size. In this paper, three different methods for size reduction are reviewed, summarized and compared with each other, such as utilizing filtering structures to replace the quarter-wavelength transmission structures of power dividing network, using couplings between the four resonators formed in a ring-type coupling topology, as well as employing one filtering structure coupled with input/output feed lines. Each method is demonstrated by one specific case.