A Crosstalk Reduction Technique for Microstrip MTL Using Mode Velocity Equalization

This paper proposes a simple method to enhance the timing margin of high-speed digital signals for multiconductor transmission lines (MTLs) in inhomogeneous media. It uses interline capacitances to implement the capacitance matrix homogenizing the original inhomogeneous structure. As a result, it equalizes the velocities of all the modes involved in the MTL structure simultaneously. The design equations are derived and the limitation of the proposed scheme is explained. For the experiment, a 100-mm three-line coupled microstrip MTL (M-MTL) is built. The measured total peak-to-peak jitter including crosstalk and other noises was 91 ps in the test structure. When the M-MTL is loaded by the proposed values of lumped capacitors between the adjacent lines, the jitter is reduced to 12 ps, whereas the measurement using the even/odd mode approach shows 22 ps jitter. All the measurement results are in good agreement with the theoretical values, which proves the effectiveness of the proposed method.