S-Parameter Analysis Pipeline
Upload up to 4 Touchstone files and get component values (L, C, R, Q, self-resonance) for a single component, plus insertion loss, return loss, group delay, TDR and passband ripple — all in one automated report.
How It Works
S-parameters (scattering parameters) describe how RF energy flows through a multi-port network. S11 is input return loss, S21 is forward transmission (insertion loss), S12 is reverse isolation, and S22 is output return loss. They are the standard language for characterising connectors, cables, PCB traces, filters, and amplifiers at RF/microwave frequencies.
This pipeline runs a fixed sequence of post-processing steps on Touchstone data and shows the result of each:
- View — magnitude, phase, group delay and VSWR for every uploaded file
- Passivity — checks that no frequency point generates energy. Small violations (largest singular value up to 1.02), typical of measurement noise, are corrected; larger ones are taken as intentionally active data, such as an amplifier, and left unmodified
- Ripple — passband insertion-loss statistics and peak-to-peak ripple
- TDR — the impedance profile along the structure
- Time gating — windows the reflection around its main discontinuity and transforms back
- Mixed-mode conversion — for 4-port files, differential and common-mode responses (SDD, SCC)
- Format conversion — S to Z, Y and ABCD. A representation a network simply does not have is named as such: a series two-port has no Z at any frequency, and a shunt two-port has no Y. Where a representation exists everywhere except at isolated frequencies — Z on a lossless half-wave line, ABCD where S21 is zero — those points alone are reported as undefined. Either way the job completes and the representations that do exist are shown
- Component extraction — when the file describes a single series or shunt element, or is a 1-port, the tool reports R, L or C, Q against frequency and the self-resonant frequency, with the mounting it assumed
- Cascade — when two or more 2-port files are uploaded, chains them over their common frequency range
Upload one to four Touchstone files (.s1p through .s4p). The port count is read from the file itself, so a file whose name disagrees with its contents still loads and the disagreement is reported.
Related Calculators
Read the Guide
FAQ
What is a Touchstone file?+
Touchstone (.snp) is the industry-standard format for S-parameter data. The extension indicates the number of ports: .s1p (1-port), .s2p (2-port), .s3p (3-port), .s4p (4-port). The file contains frequency points and complex S-parameter values in magnitude/angle, dB/angle, or real/imaginary format.
What does passivity enforcement do?+
Measured S-parameters sometimes violate passivity (the network appears to generate energy) due to measurement noise or calibration errors. At each frequency where the largest singular value of S exceeds 1 by no more than 2%, the tool clamps the singular values to 1, giving physically realisable data for simulation. A larger violation is not noise: it means the file describes an active device, such as an amplifier, and clamping its gain to unity would corrupt every later stage, so the data is left unmodified and labelled active.
When should I use time gating?+
Time gating isolates a specific impedance discontinuity (like a connector or via transition) by windowing the time-domain impulse response. Use it when you need to separate the DUT response from fixture effects without a full de-embedding calibration kit.
Can I cascade multiple S-parameter files?+
Yes. The cascade operation chains two 2-port networks in series by converting to T-parameters, multiplying, and converting back. This is useful for building up a channel model from individual measured segments (connector + trace + connector).
Why is the Z tab empty for my inductor or ferrite bead?+
Because a series two-port has no Z representation at any frequency, not because the data is bad. Open port 2 of a series element and no current flows, so Z11 = V1/I1 is undefined everywhere. Vendor component files — Murata, TDK, Coilcraft and others — are measured in series-mode connection, so this is the normal case for them. Y and ABCD are exact for such a network and are shown instead, and the component values are extracted from ABCD.
What mounting does the component extraction assume?+
It follows the topology it detects: a series two-port is read series-through, taking the series impedance from ABCD B; a shunt two-port is read shunt-through, taking the shunt admittance from ABCD C; a 1-port is read by reflection. The assumed mounting is always reported beside the values, because the same file read under the other mounting describes a different component. No de-embedding is applied — the values are the component as mounted in the file's own fixture.
Why is no self-resonant frequency reported?+
Because the reactance does not change sign anywhere in the swept range, so no self-resonance occurs in the data. The frequency range that was searched is reported alongside. Self-resonance is never extrapolated past the sweep: a part that resonates at 2 GHz measured only to 1 GHz has no SRF this tool can honestly report.
Can I upload a file whose extension is wrong?+
Yes. The port count comes from the file contents — from a [Number of Ports] keyword when present, otherwise from the number of values per frequency row. The extension is consulted only to choose between port counts the data already allows. A 1-port file named .s2p loads as a 1-port file and the mismatch is reported with the result.