Transmission line losses—driven by skin effect and dielectric properties—play a critical role in degrading high-speed signal integrity and eye performance.
Transmission line loss directly affects eye diagram quality, with around −12 dB at Nyquist marking the limit before signal integrity rapidly degrades without equalization.
Learn more about measuring and using S-parameters and and TDRs for de-embedding circuit and test fixture effects, emulating the impact of characterized components, transmission lines or test fixtures, characterizing transmission line or path quality, and de-embedding to the IEEE 370-2020 Standard for Electrical Characterization of Printed Circuit Board and Related Interconnects at Frequencies up to 50 GHz.
Broad dips in S-parameter plots typically result from stub resonances, where reflected signals interfere with the main signal path and reduce transmission at specific frequencies.
A monotonic drop-off in S21 indicates increasing signal attenuation with frequency, typically caused by dielectric and conductor losses in the interconnect.
Ripple patterns in S-parameters are caused by reflections from impedance discontinuities, with ripple spacing determined by interconnect length and ripple magnitude driven by impedance mismatch.
Sharp dips in S-parameter plots often indicate coupling to high-Q resonant structures, where specific frequencies are absorbed by PCB cavities or floating interconnects.
Understanding the differences between reflection coefficient, return loss, transmission coefficient, and insertion loss eliminates common S-parameter confusion.
Understanding when to use a TDR, WavePulser 40iX, or VNA depends on bandwidth, rise time, port count, and whether you need time-domain impedance or frequency-domain S-parameters.
