EMI Bites: Treat Your Signal Path as a Transmission Line!
Design traces to achieve a constant characteristic impedance from start to finish.
Sometimes even small variations can cause issues.
Why this causes problems:
- Characteristic impedance defines how signals travel along the line.
- If one section is 50 Ω and the next is 60 Ω, the mismatch can cause reflections.
- These reflections distort the signal and can lead not only to signal integrity issues, but also to EMI.
- If the impedance changes along the line, you no longer have a defined transmission line—hence a characteristic impedance—but multiple mismatched segments.
Key Insight:
Signal integrity depends on maintaining a single, unbroken impedance along the entire path.
How to keep impedance consistent:
- Match trace width to your PCB stackup to hit your target (e.g., 50 Ω).
- Avoid sudden geometry changes like trace width transitions or layer swaps without proper transition and design.
- Use controlled impedance routing tools and validate with simulation or field solvers (Simbeor is a great choice).
- Keep signal layers adjacent to solid return reference planes (RRP) to stabilize impedance.
To electromagnetic enlightenment,
- Dario
P.S. If you are a lead engineer in charge of high-stakes projects with zero tolerance for EMC failures
Join my free masterclass and learn the exact process I use to design boards that pass EMC tests without rework, delays, or guesswork.
Join here: https://www.fresuelectronics.com/free-training
*Qualifications apply.
#Electronics #PCBDesign #EMI #EMC #Engineering