Cable Crosstalk Calculator

Near-End Crosstalk (NEXT) estimate using a simple capacitive coupling model. Enter your line parameters to get coupled voltage and NEXT in dB, plus Show Work.

How to Use

  1. Enter the aggressor signal amplitude and frequency.
  2. Enter coupling capacitance (total or per-length) and the coupled length.
  3. Set victim load impedance (or keep the default).
  4. Review the NEXT result (dB) and coupled voltage (rms/peak estimates).

Model note: this is a simplified capacitive-coupling estimate (good for fast “what-if” checks). Real cables also have inductive coupling, geometry effects, and frequency-dependent parameters.

Coupling View
Visual feedback: coupling strength and estimated NEXT.
Vcoupled
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NEXT
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Iinj
—
Ccouple
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Indicator: —
Aggressor Victim Ccouple Zload Vs Visual: coupling highlight scales with C·f and estimated injected current.
Inputs & Settings
Capacitive NEXT estimate. Tool works fully client-side.
Use peak amplitude for sine mode. For edge mode, use step amplitude.
For sine, use fundamental. For fast edges, use an equivalent bandwidth.
If using C/Length mode, this becomes capacitance per length unit.
Length is used only in C/Length mode to compute total Ccouple.
Common: 50Ω (RF), 100Ω (diff), 1kΩ+ (high-Z logic input).
NEXT dB = 20·log10(Vref / Vcoupled_rms). Default uses 1V reference.
Quick Adjust
10 pF
100 MHz

Tip: Sliders are for quick “what-if” testing. Use unit dropdowns for exact scaling.

Used only in Edge mode. Smaller tr → more coupling (higher dv/dt).
This stays on-device. Not uploaded.
Show Work (step-by-step)
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Work is shown in base units (V, Hz, F, Ω, s) for clarity and consistency.

Capacitive NEXT Model (Quick Reference)

Capacitive coupling injects current into the victim line: Iinj ≈ Ccouple · dv/dt

  • Sine: dv/dt(pk) = 2π f · Vpk
  • Edge: dv/dt ≈ Vstep / tr
  • Victim voltage: Vcoupled ≈ Iinj · Zload (simple load model)
  • NEXT (dB): NEXT = 20·log10(Vref / Vcoupled_rms)

This tool is a fast estimator. Real NEXT depends on cable geometry, return paths, shielding, balance, and frequency-dependent parameters.

FAQ

What does “NEXT” mean?

Near-End Crosstalk is the undesired signal measured at the near end of the victim line caused by the aggressor. Higher NEXT (in dB) is better (less coupling).

Why is rise time important?

Faster edges mean higher dv/dt, which increases capacitive injection current and raises crosstalk.

Why do twisted pairs help?

Twisting improves field cancellation and balance, reducing coupling—especially over long runs.

Is this enough for compliance testing?

No—use manufacturer data, standards-based test setups, and proper instruments for compliance. This is meant for quick estimates and design intuition.

Tool Info

Last updated:

Updates may include UI improvements, more unit options, and edge-case handling.