In high-speed digital systems, signal integrity (SI) issues become especially critical as data rates increase. S-parameter (scattering parameter) testing, as an important method for analyzing the electrical performance of interconnect systems, has become a core part of high-speed design verification and simulation.

S-parameters describe the reflection and transmission characteristics of signals in multi-port networks. For example, S11 represents the reflection coefficient at a port, while S21 represents the transmission coefficient from port 1 to port 2. In high-speed interconnects, S-parameters can accurately characterize issues such as impedance discontinuities, insertion loss, return loss, and crosstalk.

In practical testing, a Vector Network Analyzer (VNA) is commonly used. Rigorous calibration (such as SOLT or TRL) is required before testing to eliminate system errors, and the measurement points should be as close as possible to the device under test to minimize lead effects.

The frequency-domain results of S-parameters can be transformed into the time domain via Fourier transform, which supports time-domain simulations (such as TDR/TDT) or can be used as simulation models for system-level SI analysis (such as IBIS-AMI simulations). As SerDes data rates reach 56 Gbps and even 112 Gbps, the industry demands higher bandwidth and greater accuracy in S-parameter measurements.

In summary, S-parameters are not only an important tool for RF systems but also play a key role in high-speed digital signal chains, helping engineers evaluate and optimize signal chain performance to improve system stability and reliability.