Symmetric tri-band balun architecture with a systematic design procedure

A new structure for a passive tri-band balun, operating at three arbitrary frequencies, is presented in this paper. The proposed technique makes effective use of the existing dual-band balun. The resulting architecture is symmetric and enables simple even- and odd-mode analysis to simplify the design equations. The simplified analysis leads to closed form equations with two free design variables. The presence of free design variables provide the opportunity to develop a simplified systematic design procedure for wide range of frequencies. The proposed technique is validated at arbitrarily chosen frequencies of 1GHz, 2GHz, and 2.5GHz in a simulation framework. Furthermore, to demonstrate the effectiveness of the proposed technique, a prototype has been developed on Rogers 5880 substrate. The obtained simulation and measurement results are in good agreement.