Generation and Mitigation of Common-Mode Noise for Differential Traces With Adjacent Ground Line and Ground Plane

Abstract

Abstract-This study investigates the generation and mitigation of common-mode noise (CMN) in a common structure which consists of differential traces with adjacent ground lines and a ground plane. For simplicity, a simple test structure similar to the common structure is proposed. The test structure is divided into three parts. One part is composed of differential traces with adjacent ground lines. The second is composed of differential traces with adjacent ground lines that are connected to a ground plane. The third comprises differential traces with an adjacent ground line and an adjacent ground plane. The generation and mitigation of CMN in these three parts are studied. Test structures with different designs are investigated to confirm the effectiveness of the CMN mitigation schemes. Based on these analyses, design guidelines for mitigating CMN are provided. The proposed design guidelines reduce the peak-to-peak CMN amplitude by 81% from that achieved using unsuitable design of test structure. In the frequency domain, the reduction of the magnitude of differential-to-common mode conversion (|S cd21 |) at the resonant peaks exceeded 40 dB in the frequency range 0 GHz ∼ 6 GHz. Finally, a comparison between simulated and measured results verifies the favorable CMN mitigation performance of the proposed design guidelines.