A bandpass filtering balun based on circular sector patch

A feasible design of balun filter is implemented using a circular sector patch element with simplicity in design and fabrication. In order to further improve bandpass filtering properties and compress the circuit size simultaneously, complementary split ring resonators are introduced on the patch element. For demonstration, two patch balun filters operating at different frequencies are fabricated and measured to validate the feasibility of the presented structures. The results of the measurement match the simulation results well.