Current Return Path Analysis in Signal Integrity

As the clock frequencies of digital systems continue to increase and signal transition times become increasingly shorter, the impact of high-speed digital interconnect design on the overall electrical performance of the system grows ever more significant. In high-speed systems, high-speed signals traveling through interconnect lines give rise to a series of signal integrity (SI) issues. The current return path is a critical concept in signal integrity analysis. This paper investigates the variations in current return paths within high-speed circuits, providing a basis for high-speed PCB design. This study focuses on analyzing important concepts in signal integrity analysis: current return paths. The results show that low-frequency current return paths are determined by resistance and return along the shortest path, but when the frequency increases, high-frequency current return paths are determined by inductance and return along the path with the smallest enclosure area. Due to the incompleteness of the ground plane, both the loop inductance and loop resistance are greater than when the ground plane is not cut.