Investigating a Guard Trace Ring to Suppress the Crosstalk due to a Clock Trace on a Power Electronics DSP Control Board

The grounded guard trace ring is usually utilized to suppress the interference in high-speed printed circuit boards or IC packages. Although the guard ring can reduce crosstalk, its performance is greatly affected by the effectiveness of its design. This paper first investigates the mechanism of the crosstalk cancelation with a grounded guard ring. The paper then discusses and analyzes several grounding patterns based on a lumped circuit model. The analysis applies to the applications where the dimensions of PCB traces are smaller than 5% of the wavelength at the highest frequency. It is found that the best grounding patterns for the guard trace ring is to ground its two ends instead of using multipoint grounding within the concerned frequency range from 10 to 200 MHz in this paper. The theoretical analysis and the developed technique are verified by electromagnetic field distribution plots and the four-ports scattering parameters that are simulated in ANSYS HFSS 3-D electromagnetic simulation software. Experiments were finally conducted to validate the analysis and the proposed technique.