4-port 10 MHz − 67 GHz Broadband Measurement of FR-4 PCB Transmission Lines for 64-Gb/s PAM-4 Signaling

In this paper, measured high-frequency responses of differential transmission lines on FR-4 based printed circuit boards (PCBs) and their analyzed results are shown. In high-bandwidth and high-frequency communication systems, characterizing the components on PCBs becomes more and more important. Assuming transmission lines for 64-Gb/s PAM-4 signaling, the measurements are carried out up to 67 GHz using 150-μm pitch GSGSG differential probes. A via-stub effect, line-direction/location dependence on electrical characteristics of transmission lines, and relation between line dimensions and higher order mode that limits line bandwidth are analyzed based on measured results.