Optimizing EMI performance through spread spectrum clock generation in relaxation oscillator-based systems

Electromagnetic interference (EMI) represents a significant challenge in modern communication and embedded systems due to the increasing integration and switching activity of digital circuits. This paper investigates the application of spread spectrum clock generation (SSCG) techniques to reduce peak EMI levels by spreading signal energy across a wider frequency band. A configurable Matlab/Simulink model of an RC-based relaxation oscillator was developed to evaluate various modulation profiles, including triangular, piecewise linear, and Hershey-Kiss (HK). To ensure compliance with international standards (CISPR, ISO, FCC), a virtual EMI receiver model was integrated instead of using simple FFT-based analysis. Simulation results show that the Hershey-Kiss profile achieves the highest EMI suppression but requires complex implementation, while the piecewise linear profile offers a comparable reduction level with lower implementation complexity. The proposed model provides a fast pre-silicon evaluation of SSCG parameters and guidelines for optimizing modulation strategies, balancing EMI reduction performance, implementation complexity, and regulatory compliance.