Near-End Crosstalk
NEXT = Kb × length
Quick answer
This calculator solves NEXT = Kb × length for Crosstalk (dB). With Coupling Factor (dB/m) 0.5 dB/m, Coupled Length 1 m, the result is 0.5 dB. It solves in 3 directions, so you can enter the values you have and get the one you need.
Calculator
Formula
Description
Near-end crosstalk (NEXT) occurs when a signal on one trace induces a coupled signal on an adjacent trace, measured at the same end as the aggressor source. For electrically short coupled lines, NEXT increases linearly with coupled length in this model, with no saturation limit. The coupling factor Kb depends on trace spacing, distance to the ground plane, and the dielectric environment. Increasing the spacing between traces or reducing the distance to the ground plane reduces crosstalk.
Variables
- NEXT — Near-end crosstalk level (dB)
- Kb — Backward coupling coefficient per unit length (dB/m)
- length — Length of parallel (coupled) routing (m)
Practical Notes
The 3W rule (space traces 3 times the trace width apart, center-to-center) reduces crosstalk to approximately -70 dB, sufficient for most digital designs. For sensitive analog signals, use guard traces or route on different layers. Stripline has lower crosstalk than microstrip because the ground planes confine the electromagnetic fields. Far-end crosstalk (FEXT) follows different rules and is proportional to coupled length in all cases.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| NEXT | Crosstalk (dB) | dB | dB |
| Kb | Coupling Factor (dB/m) | — | dB/m |
| len | Coupled Length | m | mm, cm, m, km |
Step by step
- 1. What you know: Coupling Factor (dB/m) 0.5 dB/m, Coupled Length 1 m
- 2. The relation: NEXT = Kb × length
- 3. Substitute: Kb = 0.5 dB/m, len = 1 m
- 4. Result: Crosstalk (dB) = 0.5 dB
Worked examples
Minimum range
Given: Coupling Factor (dB/m) 0.025 dB/m, Coupled Length 1 mm
Result: Crosstalk (dB) = 2.5 × 10⁻⁵ dB
Low range
Given: Coupling Factor (dB/m) 0.25 dB/m, Coupled Length 10 mm
Result: Crosstalk (dB) = 0.0025 dB
Typical
Given: Coupling Factor (dB/m) 0.5 dB/m, Coupled Length 1 m
Result: Crosstalk (dB) = 0.5 dB
High range
Given: Coupling Factor (dB/m) 0.8 dB/m, Coupled Length 100 m
Result: Crosstalk (dB) = 80 dB
Maximum range
Given: Coupling Factor (dB/m) 8 dB/m, Coupled Length 1 km
Result: Crosstalk (dB) = 8000 dB
Solving for each variable
Solve for Crosstalk (dB)
Coupling Factor (dB/m) 0.025 dB/m, Coupled Length 1 mm → 2.5 × 10⁻⁵ dB
Solve for Coupling Factor (dB/m)
Crosstalk (dB) 0.3 dB, Coupled Length 1 mm → 300 dB/m
Solve for Coupled Length
Crosstalk (dB) 0.3 dB, Coupling Factor (dB/m) 0.025 dB/m → 12 m
How Crosstalk (dB) changes with Coupling Factor (dB/m)
| Coupling Factor (dB/m) (input) | Crosstalk (dB) (result) |
|---|---|
| 0.05 dB/m | 0.05 dB |
| 0.125 dB/m | 0.125 dB |
| 0.25 dB/m | 0.25 dB |
| 0.375 dB/m | 0.375 dB |
| 0.5 dB/m | 0.5 dB |
| 0.75 dB/m | 0.75 dB |
| 1 dB/m | 1 dB |
| 2 dB/m | 2 dB |
| 3.5 dB/m | 3.5 dB |
| 5 dB/m | 5 dB |
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<p><a href="https://vbatpower.com/formulas/crosstalk-near/">Near-End Crosstalk</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate Near-End Crosstalk?
Use NEXT = Kb × length. With Coupling Factor (dB/m) 0.5 dB/m, Coupled Length 1 m, Crosstalk (dB) works out to 0.5 dB.
What is the formula for Near-End Crosstalk?
The formula is NEXT = Kb × length. Near-end crosstalk (NEXT) occurs when a signal on one trace induces a coupled signal on an adjacent trace, measured at the same end as the aggressor source.
How do you find Coupling Factor (dB/m) when you know the other values?
Rearrange for Coupling Factor (dB/m): with Crosstalk (dB) 0.3 dB, Coupled Length 1 mm, Coupling Factor (dB/m) is 300 dB/m.
How do you find Coupled Length when you know the other values?
Rearrange for Coupled Length: with Crosstalk (dB) 0.3 dB, Coupling Factor (dB/m) 0.025 dB/m, Coupled Length is 12 m.
Related Concepts
All PCB & Traces formulas →Need more features?
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