Crosstalk Reduction in Coupled Microstrip Lines using Interdigital Split on Reference Plane

The proximity of microstrip lines in compact and dense designs leads to unwanted electromagnetic coupling, resulting in crosstalk that needs to be minimized. Various methods have been explored in the literature, including via fencing, guard trace, guard trace with via, serpentine guard trace, serpentine guard trace with vias, and serpentine microstrip lines. However, these approaches often necessitate additional spacing between the microstrip lines, difficult to fabricate, and offer limited crosstalk reduction. Hence, we propose a planar interdigital split consisting of conductive strips, arranged in a fashion similar to interdigital capacitor, and are incorporated within the space available on reference plane between the coupled microstrip lines. That is, no additional space between the lines is required for crosstalk reduction. Electromagnetic simulations are conducted using a 75x45mm RO4003 Rogers PCB within the frequency range of 1-8GHz. The results shows a significant improvement of 19dB compared to utilizing a solid ground on the reference plane. Moreover, the efficacy of the proposed interdigital split approach is reinforced by meticulous parametric analyses. These analyses can assist designers in fine-tuning the interdigital split parameters to achieve crosstalk minimization at specific frequencies.