A Simple and Effective Method for Designing Frequency Adjustable Balun Diplexer With High Common-Mode Suppression

A simple and effective structure based on traditional coupled-line theory and the configuration of folded open-loop ring resonators (OLRRs) was used to design a balanced-to- unbalanced (balun) diplexer. The two resonant frequencies of the balun diplexer are easily adjusted by changing the physical dimensions of OLRRs and microstrip lines and they had high common-mode suppression. In this study, the designed balun diplexer is investigated for LTE (2.6 GHz) and WLAN (5.2 GHz) band applications.