Undesired Resonances in High-Speed Differential Pair due to Non-Ideal Return Path Design

This paper studies a specific G-S-S-G style high-speed differential pair. Simulation shows that resonances exist in both common- and differential-mode signals. With the further investigation, it turns out to be that a quarter-wavelength resonant structure is incautiously created, which is responsible for the resonances. To remove the resonances, two methods are recommended in this paper. Each method has its own benefits and limitations. The proposed solutions can be treated as design rules when similar differential pairs are designed.