Stripline
What Is a Stripline?
A stripline is a transmission line configuration where a copper trace is routed on an inner layer of the PCB, sandwiched between two reference planes (typically ground planes). The two surrounding planes provide electromagnetic shielding on both sides of the trace, containing the electric field within the dielectric and significantly reducing radiation loss, crosstalk, and susceptibility to external interference compared to microstrip traces on outer layers.
Stripline is the preferred routing configuration for the most sensitive high-speed signals, including multi-gigabit serial interfaces, clock distribution networks, and signals with strict EMC requirements. The characteristic impedance of a stripline trace depends on the trace width, the distance to each reference plane, and the dielectric constant of the surrounding material. Because the trace is embedded in a homogeneous dielectric (unlike microstrip, where one side is exposed to air), stripline impedance calculations are more predictable and the propagation velocity is more consistent.
Layer-Aware Routing Strategy With AI
Choosing between microstrip and stripline routing for each signal group is a key layout strategy decision that affects impedance accuracy, crosstalk performance, EMC compliance, and layer utilization. Physics-driven AI layout engines can make these layer assignment decisions automatically based on each signal's sensitivity requirements, routing the most critical nets as striplines on inner layers while using microstrip on outer layers for less sensitive connections. This signal-aware layer assignment optimizes both electrical performance and routing density without requiring the manual prioritization and layer planning that traditional layout demands.





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