Abstract
Abstract
This paper proposes a new general rotationally symmetric coupled feeding structure and its applications to the design of single- and dual-band balanced filters for high common-mode (CM) suppression. The balanced feeder consists of two coupling lines coupled with a ring resonator, which can be either a uniform impedance ring resonator or a stepped impedance ring resonator. Under differential-mode (DM) excitation, the voltage distributions of the coupling-line and resonator are both rotationally even-symmetric and the total coupling coefficient adds up, which indicates that the proposed feeding structure can achieve DM transmission characteristic. Under CM excitation, their voltage distributions are rotationally even- and odd-symmetric, respectively, so the total coupling coefficient cancels out to zero and CM suppression property is achieved. For demonstration, four single- and dual-band balanced filters with wide range of CM and harmonic suppression are designed, fabricated, and measured, and the simulation and measured results match well.
Funder
National Natural Science Foundation of China
State Key Laboratory of Millimeter Waves
High Performance Computing Center of Central South University