VNA-based Insertion Loss and Return Loss Testing and De-embedding Techniques for High-Speed Serial Links on PCBs

Abstract

This paper addresses the critical requirements of high-speed communication systems within artificial intelligence (AI) data centers, focusing on both theoretical analysis and practical implementation. The study begins with a detailed examination of the Vector Network Analyzer (VNA) measurement principle and the definition of S-parameters, providing an in-depth explanation of the physical significance of key parameters, including S11 and S21. The relationship between insertion loss and return loss is explored, highlighting their influence on signal fidelity and overall system performance. Furthermore, the characteristics of high-speed serial links are analyzed in conjunction with Pulse Amplitude Modulation 4-level (PAM4) signaling, emphasizing the effects of test indicators such as channel insertion loss flatness, group delay, and return loss margin on signal integrity. The paper also elaborates on the design and construction of the test system, including the deployment of de-embedding techniques to isolate and accurately measure channel effects. Experimental verification is conducted to assess system performance, with results analyzed to demonstrate the practical impact of different signal impairments on high-speed data transmission. Insights derived from the study provide valuable guidance for engineers and researchers involved in the design, testing, and optimization of high-speed interconnects in AI-driven data centers, offering concrete recommendations for improving signal reliability and overall communication efficiency.