Please enter all required values.
RESULTS
Input Parameters Specification
Trace ThicknessCopper thickness of each broadside coupled stripline conductor. Thickness affects conductor geometry and impedance behavior.
Substrate HeightDielectric height between the reference planes. This stack-up dimension strongly affects stripline impedance.
Trace WidthWidth of the stacked broadside traces. Wider conductors usually reduce impedance.
Trace SpacingVertical separation between the two broadside coupled traces. Smaller spacing increases coupling.
Dielectric ConstantRelative permittivity of PCB material used in the supplied broadside stripline formula.
Output ValuesOdd, even, common and differential impedance are shown for controlled-impedance PCB design.
Practical Operational Examples
Differential Pair Stackup
Estimate broadside coupled stripline odd/even mode impedance in multilayer PCB designs.
Controlled Impedance
Adjust width, spacing, height and dielectric constant to target differential impedance.
High-Speed Routing
Useful for stacked differential pairs in dense multilayer boards where edge-coupled routing is not practical.
PCB Manufacturer Review
Use the result as an early design estimate before confirming final impedance with board house stack-up data.
Diagrams & Theory
Broadside coupled stripline uses two conductors stacked vertically inside the dielectric between reference planes. Coupling is mainly controlled by vertical spacing and trace width.
Formulas & Mathematical Logic
The calculator preserves the supplied broadside coupled stripline impedance JavaScript formula and unit multipliers.
The helper function findk searches for the best coupling parameter k from the trace width, substrate height and spacing relationship.
Odd impedance is calculated from substrate height, spacing, dielectric constant and coupling parameter k.
Even impedance is calculated from dielectric constant and elliptic integral approximation.
Common impedance = Even impedance / 2.
Differential impedance = 2 × Odd impedance.
Practical meaning: smaller vertical spacing increases coupling, which changes odd-mode and differential impedance.
Step-by-Step Example
Example: trace thickness = 1 mil, substrate height = 20 mil, trace width = 8 mil, trace spacing = 8 mil, dielectric constant = 4.2.
The calculator converts trace thickness, substrate height, width and spacing using selected unit multipliers.
The coupling parameter k is estimated using the original iterative search logic.
Odd-mode and even-mode impedance are calculated first.
Common-mode impedance is derived from even-mode impedance.
Differential impedance is derived from odd-mode impedance.
How to Use This Calculator
Enter copper trace thickness and select the correct unit.
Enter substrate height between reference planes.
Enter broadside trace width.
Enter vertical trace spacing between coupled conductors.
Enter dielectric constant of the PCB laminate.
Click Calculate to get odd, even, common and differential impedance.
About This Calculator
Estimate broadside differential impedance for multilayer PCB stackups.
The CalcBoy Broadside Coupled Stripline Impedance Calculator estimates odd-mode, even-mode, common-mode and differential impedance for vertically stacked coupled traces.
Broadside coupled stripline is used when two signal conductors are stacked vertically on different internal layers instead of sitting side-by-side on the same layer. This structure is useful in dense multilayer PCBs, controlled-impedance routing and some high-speed differential pair layouts where board area is limited or a specific coupling behavior is needed.
The calculator uses trace width, vertical spacing, dielectric height, copper thickness and dielectric constant to estimate modal impedances. Odd-mode impedance is important for differential signaling, while even-mode impedance helps describe common-mode behavior. From those values, differential and common impedance are derived for practical PCB design review.
This tool is helpful for early stack-up exploration, but final production impedance should be confirmed by the PCB manufacturer. Real board results can shift because of lamination tolerance, copper plating, resin content, glass weave, dielectric variation and fabrication process.
Best UseBroadside-coupled stripline differential impedance estimates.
Supported OutputsOdd, even, common and differential impedance.
Helpful ForDense multilayer boards, differential pairs and controlled-impedance stackups.
Design ReminderConfirm final impedance with your PCB manufacturer’s stack-up.
Tip: Broadside coupling is very sensitive to vertical layer spacing. Small dielectric thickness changes can noticeably move differential impedance.
Frequently Asked Questions
What is broadside coupled stripline?
It is a coupled transmission line structure where two traces are stacked vertically inside a PCB dielectric between reference planes.
What is odd-mode impedance?
Odd-mode impedance is the impedance when the coupled traces carry equal and opposite signals, as in differential signaling.
What is even-mode impedance?
Even-mode impedance is the impedance when both traces move together with the same polarity.
How is differential impedance calculated?
Differential impedance is calculated as two times odd-mode impedance.
Why does trace spacing matter?
Vertical spacing controls coupling strength. Smaller spacing usually increases coupling and changes differential impedance.
Can this replace PCB manufacturer impedance control?
No. Use it for estimation, then confirm final controlled impedance with the PCB manufacturer’s stack-up and impedance report.
Related Calculators
Edge Coupled Stripline Impedance CalculatorCalculate odd, even, common and differential impedance for side-by-side striplines.
Symmetric Stripline Impedance CalculatorCalculate single-ended stripline impedance for centered embedded traces.
Microstrip Impedance CalculatorCalculate top-layer PCB trace impedance from width, height and dielectric constant.
Stripline Crosstalk CalculatorEstimate crosstalk between embedded PCB traces.