Wideband Three-Way FPD With Unequal Division Ratio Based on Coaxial-to-RWG Transition

A simple design approach of wideband three-way filtering power divider (FPD) with unequal division ratio based on coaxial-to-rectangular waveguide (RWG) transition is investigated. The bandpass filtering response is achieved using high-pass characteristic of RGW and bandgap characteristic of coaxial-to-RWG transition improved by loading T-type resonators. The allocation of power depends solely on the distance between the outputs and the central plane of the rectangular cavity. Meanwhile, the filtering functions and power splitting are independent of each other, achieving sharped roll-off of the upper stopband and unequal power division ratio. For validation, a wideband unequal FPD with center frequency at 4.1 GHz and with 3-dB fractional bandwidth (FBW) of 58.5% is designed, simulated, and fabricated. The insertion loss (IL) of all three outputs is less than 0.4 dB (excluding ideal loss), demonstrating the advantage of low loss in the rectangular cavity.