Signal Integrity Issues in High-Speed Interconnects Over a Ground Plane Aperture

Abstract

In this paper, we present a critical analysis of the signal integrity issues in high-speed interconnects over an aperture in the ground plane below the interconnect line. In that we report closed-form expressions for the line capacitance and inductance and damping factor using variational analysis combined with transmission line technique. It is seen that the presence of a ground plane aperture can result in substantial decrease in the line capacitance, thus resulting in lower damping factor and increased signal overshoots and undershoots. These overshoots may severely deteriorate signal integrity as well as aggravate crosstalk in coupled interconnect lines over such an aperture and must be carefully addressed in applications where the use of ground plane aperture is common. These applications include microstrip couplers, bandpass filters, split rings and high-impedance lines. The proposed analytical model is verified using FDTD simulations and measurements.