💡 Left-click plot to add a permanent marker
Freq: —
No Data Loaded
Drag & drop SnP files anywhere on the plot
📥
Drop SnP files to plot
S1P, S2P, S3P … S10P supported
📍
Drop marker here
Release to place readout card on plot
Freq: —
💡 Shift + Scroll to highlight · Esc to clear
Ready — drop SnP files to begin
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Graph Title & Screenshot

Cascade S-Parameters

Cascade multiple loaded N-port S-parameter files in series. Choose which port maps to input and output.

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S-Parameter Viewer & Plotter — User Guide

Online Touchstone SnP analyser · TDR/TDT · Cascade · Transmission Line Modelling

Loading Files

  • Drag & drop any Touchstone SnP file directly onto the plot area. Supports S1P through S10P (1–10 port networks).
  • Open Files button in the top-right loads one or more files via the file picker. Multiple files can be loaded simultaneously and toggled independently.
  • Right-click a file in the trace list to download it as a Touchstone SnP file or CSV (for TDR traces).
  • Clear All removes every loaded file and resets the view.

Navigating the Plot

  • Scroll wheel — zoom in/out on the X-axis around the cursor position.
  • Click & drag on the plot area — pan left/right along the active axis.
  • Shift + drag on the plot area — drag to zoom: draw a selection box to zoom the X-axis into that exact range.
  • Auto-Scale button or press A — fits both axes to all visible trace data instantly.

Display Format & Scale

  • Format — switch between dB Magnitude, Linear Magnitude, Phase (°), Real Part, and Imaginary Part in the sidebar settings.
  • Freq Unit — force the X-axis to display in Hz, kHz, MHz, or GHz; Auto selects the most readable unit automatically.
  • Line Width — adjust trace line thickness in the sidebar.
  • X / Y Axis — set to Manual to enter precise numeric limits, then click Apply Limits or press Enter. Auto-Scale always overrides manual limits.

Live & Pinned Markers

  • Live Marker — hover over the plot to see real-time values for every visible trace in the floating tooltip. Toggle with the Live Marker button or press L.
  • Pinned Markers (M1, M2…) — left-click anywhere on the plot to drop a permanent red marker. A popup lets you target all files or just one. The marker card shows interpolated values for every visible trace.
  • Edit marker position — click the frequency/time value in the Pinned Markers panel to edit it directly. Type a value with a unit suffix for instant commit:
    • Frequency mode: 2.4g = 2.4 GHz · 500m = 500 MHz · 1.5k = 1.5 kHz
    • Time mode: 5n = 5 ns · 2u = 2 µs · 1m = 1 ms
    • Distance mode: 1.2m = 1.2 m · 50mm = 50 mm (type suffix then Enter)
  • Drag a marker — hover near a pinned marker line until the cursor changes, then drag left/right to reposition it.
  • Drag to plot — drag a marker card from the sidebar panel onto the plot to reposition its readout card on the canvas.
  • Delta Markers (ΔM1, ΔM2…) — place a second marker and choose Δ from Mx in the popup. The delta marker shows the offset from the reference in both X (frequency/time/distance) and Y (amplitude). The ΔX field in the panel is editable — type a relative offset (e.g. +100m = +100 MHz from reference) and press the suffix key or Enter.
  • Remove a marker — click its tab at the top of the plot, or use the ✕ button in the Pinned Markers panel.

TDR / TDT Transform

  • TDR Transform computes a time-domain reflectometry waveform from any frequency-domain S-parameter trace using an inverse DFT with selectable windowing.
  • Output types — Step Impedance (Ω), Reflection Coefficient (ρ), Step Transmission, or Impulse Response.
  • Frequency limits — restrict the transform to a sub-band to isolate features or suppress high-frequency noise.
  • DC Extrapolation — Linear or Constant extrapolation to DC improves step-response baseline accuracy when the file doesn't start at 0 Hz.
  • Windowing — apply a Hann window to reduce Gibbs ringing at the cost of slightly lower time resolution.
  • Max Time (ns) — sets the time record length; the tool auto-suggests an alias-free limit based on the file's frequency spacing.
  • Velocity Factor (VF) & Relative Permittivity (εr) — enter either one and the other calculates automatically (εr = 1/VF²). When set, the X-axis converts to physical distance. Leave both blank for a time axis.
  • TDR X Axis — switch between Time and Distance views in the sidebar after plotting (only visible when a distance-converted trace is loaded).

Cascade Networks

  • Click Cascade Networks in the toolbar to open the cascade dialog. Select two or more 2-port (or higher) files.
  • Choose the Input and Output ports for each network and reorder them with the up/down arrows.
  • Calculate & Plot — cascades all networks in order using T-matrix (transfer matrix) multiplication and adds the result as a new file. All source files are hidden automatically; re-enable them via the sidebar checkboxes.
  • Export — download the cascaded result directly as a Touchstone .s2p file.

Transmission Line Modelling (Tx Line)

  • Synthesise an ideal 2-port transmission line by entering: characteristic impedance (Z₀ Ω), electrical length in degrees at a reference frequency (Fref), and path attenuation in dB at Fref.
  • Loss Scaling Law — √f for skin-effect conductor loss, f for dielectric loss, Flat for frequency-independent loss.
  • Lines with Z₀ ≠ 50 Ω automatically produce realistic S₁₁/S₂₂ reflection terms and mismatch ripple.
  • Plot Line — generates a standalone SnP file. Plot & Cascade — appends the line in series with all currently visible frequency-domain networks.

Smith Chart

  • Select Smith Chart from the Format dropdown in the sidebar. All visible frequency-domain S-parameter traces are plotted on a standard 50Ω normalised Smith chart.
  • The chart shows constant-resistance circles (R = 0, 0.2, 0.5, 1, 2, 5, 10) and constant-reactance arcs (X = ±0.2, ±0.5, ±1, ±2, ±5, ±10). The centre is Z₀ (50Ω matched). SHORT is the left edge (Γ = −1), OPEN is the right edge (Γ = +1).
  • Direction arrows on each trace show the direction of increasing frequency.
  • Live Marker — hover over the chart to snap to the nearest frequency point. The tooltip shows the complex impedance Z = R + jX (in Ω) and the reflection coefficient Γ (magnitude and angle).
  • Pinned Markers — click anywhere inside the chart to pin a marker at the nearest frequency on the closest trace. Works the same as in other modes.
  • Time-domain (TDR) traces are not displayed in Smith mode. Switch to a frequency-domain format to use TDR.

Export & Screenshot

  • Screenshot — downloads a high-resolution transparent PNG of the current plot. Optionally add a title before saving.
  • Right-click any file in the trace list to download it as a Touchstone SnP file (frequency-domain) or a CSV file (TDR/time-domain traces).

⚠ Accuracy Notice

This tool provides rapid first-order visual approximations. TDR calculations use uniform frequency resampling and numerical integration. For mission-critical, tape-out, or production validation always cross-verify with industry-standard offline EDA software or high-precision simulation suites.