High-Performance Common- and Differential-Mode Reflectionless Balanced Band-Pass Filter Using Coupled Ring Resonator
Yifan Zhang, Yongle Wu, Weimin Wang, Jie Yan
Abstract
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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda /2$ </tex-math></inline-formula> 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.