An Analysis of Electromagnetic Signatures From Triangularly Modulated Spread Spectrum Clocking Signals

This article treats an analysis of electromagnetic (EM) radiation signatures from devices employing spread spectrum clocking, primarily focusing on the widely used protocol named flat panel display link (FPD-link). FPD-link periodically changes its clock rate, radiating relatively broad bandwidth electromagnetic fields. This feature necessitates a different approach in the area of signal reconstruction using their EM signature. Previous research has relied on frame-averaging techniques to enhance the signal-to-noise ratio (SNR) in the presence of faint EM signal. However, coherent frame-averaging, once considered the most efficient method, is now physically unfeasible because of the clock periodicity variation, and accordingly, the only viable approach with SNR enhancement to some extent is incoherent frame-averaging providing definitely limited performance. In response to this challenge, the authors conduct a thorough analysis of the phenomena generated by spread spectrum clocking-induced EM signature, subsequently, proposes a circumventing scheme named as partial-coherent frame-averaging, aiming to partially overcome the limitations of unavailability of coherent synchronization. Finally, the effectiveness of proposed scheme is validated through multiple experiments, comparing it to incoherent frame-averaging method. This article contributes to a deeper understanding of signal reconstruction using EM signatures from spread spectrum clocking-based devices, and provides potential countermeasures based on their practicality.