Design of a New Dual-Band Balanced-to-Balanced Filtering Power Divider Based on the Circular Microstrip Patch Resonator

A novel compact dual-band balanced-to-balanced (BTB) filtering power divider (FPD) based on the circular microstrip patch resonator is presented, for the first time in this brief. Firstly, in order to elucidate its principle of operation, the resonant property of the circular microstrip patch resonator is researched. After that, a prototype of the dual-band BTB FPD is developed. It is mainly constructed by two coupled circular patch resonators, two impedance matching ports, and three pairs of balanced ports. Its operating mechanism can be strictly illustrated by the field distributions of the concerned resonant modes. Hereinto, desired dual-band balanced filtering response is attained by elaborately exploiting TM
₁₁
and TM
₃₁
modes while suppressing other modes from the patches. Ultimately, for validation, a dual-band BTB FPD centered at 4.2 GHz and 9.4 GHz is designed, fabricated, and tested. Good agreement between simulated and measured results validates that expected differential mode (DM) response, prominent DM isolation, nice common-mode (CM) suppression, high selectivity, and satisfactory harmonic suppression.