High-Performance Common- and Differential-Mode Reflectionless Balanced Band-Pass Filter Using Coupled Ring Resonator

In this brief, for the first time, we propose common-mode (CM) and differential-mode (DM) reflectionless balanced bandpass filters (BPFs) using half-wavelength ring resonator. By loading absorptive stubs at input/output ports and the ends of the coupled-lines (CLs), the BPFs can realize input-/two-port wideband CM and DM reflectionless performance from dc, as well as wide filtering band and all-stop CM suppression. As for the input-reflectionless type, two extra transmission zeros (TZs) can be obtained by loading lambda/2 stubs between the CLs. Besides, the impedances of the CLs can determine the CM suppression level, and the absorption performance can be independently adjusted. The operational foundations and explicit equations are discussed and derived. Good agreements between the simulated and measured results verify the design theory.

Automated summary

In this paper, common-mode and differential-mode reflectionless balanced bandpass filters using half-wavelength ring resonator are proposed for the first time. By loading absorptive stubs and utilizing specific design techniques, the filters can achieve wideband reflectionless performance and robust common-mode suppression. The simulated and measured results confirm the feasibility of the design theory.