Neutron STEM Lab
Virtual engineering lab

S-Parameters & Virtual Network Analyzer

Sweep ideal two-port networks or import a Touchstone .s2p file. Inspect reflection, transmission, group delay, reciprocity, and passivity.

Electrical Engineering / RF & MicrowaveadvancedValidated educational model
Learning mode

Guided laboratory

Use the checklist when you want a structured lab. Explore mode leaves the instruments unrestricted.

Explore a model

Set up your experiment

Read the equations

Start with an example, change one input, then run again. Inactive controls do not apply to the selected model. Results and validation always belong to the last completed run.

Real resistance or reference impedance.
Positive frequency; stored internally in hertz.
Positive frequency; stored internally in hertz.

Choose an example or use the default settings, then run the experiment.

Import your own two-port network

Touchstone 1.x .s2p, RI / MA / DB, up to 2 MB and 2,001 samples. Both ports must use the same real reference impedance. Version 2 keywords, mixed-mode, and noise data are not supported.

Using the demonstration network. Imported data will use the file’s reference impedance.

Keep this experiment

Your setup stays in this browser. A project file preserves SI inputs, display units, receiver stages, and any imported complex network samples.

Changes are saved on this device when the settings are valid.

Measurements

Instrument readings

Actual probe sample
—
Recorded from the current model setup; rerun after editing inputs.
Forward transmission magnitude
—
Recorded from the current model setup; rerun after editing inputs.
Input reflection magnitude
—
Recorded from the current model setup; rerun after editing inputs.
Theory

Equations and model

Waves at two ports

The incident-wave vector a and outgoing-wave vector b are related by the scattering matrix. The first index is the response port; the second is the excited port. Other ports are terminated in the reference impedance. This lab uses a single equal, real reference at both ports.

[b1b2]=[S11S12S21S22][a1a2]\begin{bmatrix}b_1\\b_2\end{bmatrix}=\begin{bmatrix}S_{11}&S_{12}\\S_{21}&S_{22}\end{bmatrix}\begin{bmatrix}a_1\\a_2\end{bmatrix}P2,outP1,inc=∣S21∣2(a2=0)\frac{P_{2,\mathrm{out}}}{P_{1,\mathrm{inc}}}=|S_{21}|^2\quad(a_2=0)

Network diagnostics

A passive network cannot deliver more power than it receives for any combination of incident waves. Reciprocity and passivity are separate properties. Group delay uses the slope of unwrapped transmission phase and needs adequate frequency resolution.

λmax⁡(S†S)≤1\lambda_{\max}(S^{\dagger}S)\leq1S12=S21for a reciprocal two-portS_{12}=S_{21}\quad\text{for a reciprocal two-port}τg=−12πdarg⁡S21df\tau_g=-\frac{1}{2\pi}\frac{\mathrm d\arg S_{21}}{\mathrm df}
Validation

Independent checks

Published reference caseNot run

Check the model against a known numerical benchmark.

Expected
—
Simulated
—
Error
—
Tolerance
0.00001%

Run the experiment to perform this check.

Current model applicabilityNot run

Check current assumptions and report any limitations.

Expected
—
Simulated
—
Error
—
Tolerance
0%

Run the experiment to perform this check.

Engineering interpretation

Run the experiment to generate an engineering interpretation.

Assumptions and limitations
Assumptions
  • All calculations run locally; frequencies and lengths are stored in SI units.
  • The selected steady-state ideal or approximate model is appropriate to the engineering question.
  • Each experiment states its reference impedance, sign convention, and omitted effects.
Limitations
  • Model benchmarks validate the implementation, not a particular fabricated device.
  • Plots and sweeps have bounded resolution; inspect raw samples and refine a real measurement when required.
  • Guided completion requires current measurements and passing applicability checks. A warning scenario can still be useful for learning.
Local experiment export

Save your measurements and setup

Exports are generated in your browser. No account or server upload is required.

Settings JSON
Current parameters and instrument controls, including waveform, output enable, scope coupling, timebase, trigger, and cursors when present. Data labs also include the dataset, mappings, exclusions, budget, or propagation setup.
Measurements CSV
Completed instrument readings with labels, units, and descriptions.
Plot PNG
The current canvas-based scope, transient, sweep, or statistics visualization when available.
Summary
Markdown report with objectives, setup, measurements, validation, interpretation, assumptions, and graded guided concept-check results.

Ready to export the current local experiment state.

Learning objectives

What this experiment should establish

  • Sweep the reference filter.
  • Inspect an actual sample.
  • Test delay and attenuation.
  • Preserve the evidence.
Check your understanding

Questions to answer from the experiment

  1. What does S21 describe?
  2. Why check the largest eigenvalue of S†S rather than only S11?
  3. Which condition can make a group-delay estimate unreliable?
  4. With equal real references and a matched receiving port, |S21| = 0.5 corresponds to what forward power ratio?
Continue learning
RF & Microwave LabContinue with the other five RF experiments.AC Circuits WorkbenchReview phasors, reactance, and sinusoidal steady state.Data & Uncertainty LabAnalyze exported numerical data and measurement uncertainty.

Sources and model review

Reviewed 2026-09-17. The educational model exposes its assumptions and validation; source references do not imply external certification.