S-Parameter Analysis Pipeline
Upload up to 4 Touchstone files and get insertion loss, return loss, group delay, TDR impedance profile, 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 tool automates the most common post-processing steps on Touchstone data:
- View — magnitude, phase, group delay, VSWR plots
- Passivity enforcement — corrects measurement artefacts that violate energy conservation
- Mixed-mode conversion — converts single-ended 4-port data to differential/common-mode (SDD, SCC)
- Time gating — IFFT to time domain, apply a gate window to isolate a specific discontinuity, then FFT back
- De-embedding / Cascading — remove fixture effects or chain multiple networks
- Format conversion — convert S to Z, Y, or ABCD parameters
- Rational fitting — fit a pole-residue model for time-domain circuit simulation (SPICE)
Upload one or more Touchstone files (.s1p through .s4p) and select the operations you need. The pipeline executes them in order and shows results at each stage.
Related Calculators
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. Passivity enforcement adjusts the S-matrix at each frequency so that all singular values are at most 1, ensuring physically realisable data for simulation.
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.
What is rational fitting used for?+
Rational fitting (vector fitting) approximates the S-parameter data with a pole-residue model. This model can be exported to SPICE-compatible circuit netlists for time-domain simulation, enabling accurate channel simulation in tools like HSPICE or ADS.
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).