Balanced-to-Single-Ended Out-of-Phase Filtering Power Divider With Continuously Tunable Center Frequency and Bandwidth Using Compact Patch Resonators

This paper presents a novel compact balanced-to-single-ended out-of-phase filtering power divide with continuously tunable center frequency and bandwidth. By introducing a T-shaped slot on the isosceles right triangle patch resonator to perturb the TM10 mode and exploring varactors-loaded stubs, a new tunable miniaturized patch resonator is created. The proposed filter comprised three new tunable patch resonators connected by back-to-back varactors to adjust bandwidth in between. By studying the electric field distribution of the odd mode TM10 and grounded isolation resistors, the wished out-of-phase output signal and good port-to-port isolation can be generated. Based on such a simple structure, a balanced-to-single-ended out-of-phase filtering power with tunable bandwidth is designed and realized with a center frequency tuning range covering from 1.60 to 1.95 GHz (19.7%) and 3-dB bandwidth tuning range covering from 265 to 328 MHz at 1.90 GHz.