Decoupling capacitors

Via placement and trace geometry significantly affect decoupling capacitor performance. This final installment of a three-part series presents conducted emissions measurements across six PCB via topologies, revealing how distance from the power-ground plane pair and via spacing impact EMC results.

Conducted emissions testing on custom PCBs shows how moving a decoupling capacitor farther from an IC can increase emissions across multiple frequency bands. Using CISPR 25 methods, this study compares capacitor placements and via topologies to reveal how distance and inductance shape PDN behavior.

Explore how PCB via and trace geometry influence the real‑world effectiveness of decoupling capacitors. This first article in the series defines six board variants, capacitor placement strategies, and PCB topologies, setting the stage for upcoming RF emission results based on CISPR 25 testing.