Study on the effects of distortions and common-mode noise in high-speed PAM-4 systems
A study of different distortions in high-speed differential PAM-4 signals, including the linear distortions, i.e. amplitude mismatch, channel skew and bandwidth mismatch, and the non-linear distortion, i.e. the mismatch between rising and falling edges is presented. It is observed that only the non-linear distortion introduces a large common-mode (CM) noise at the double Nyquist frequency, which causes electromagnetic interference (EMI) in high-speed serial links. At last, Monte-Carlo simulations are performed to investigate the impact of signal distortions on the EMI-related CM noise.
