Home Touchstone 2-port S-parameter plotter (.s2p)

Single file

• Select Mode → Single file.
• Upload a .s2p (2-port) or .s1p (S11 only) file.
• Use Range to set start/stop frequencies.
• Use Traces to toggle S11/S21/S12/S22 and Smith for Γ plots (S11/S22).

Cascade (7 blocks)

• Select Mode → Cascade.
• Set design Z0 (used for renormalisation, cascade maths, Smith chart and exports).
• Configure each block as Bypass, Gain/Loss (dB), or Upload.
• At least one uploaded .s2p/.s1p file is required for cascade analysis (it defines the frequency grid).
• Click Compute cascade to generate the cascaded S-parameters.
• Use the normal Traces / Smith controls to view the result.
• Use Save design / Load design to return to a line-up later.
• Use Export CSV or Export .s2p to export the computed cascade.

Touchstone parsing

• Supports Touchstone v1 option line (# ... R Z0) and common Touchstone v2 keywords (e.g. [Version], [Network Data], [Two-Port Data Order]).
• .s1p is treated as an S11-only network (single-file mode), or can be used at cascade block 1 or 7.

Frequency grid

• For cascades, the frequency axis is taken from the first uploaded file and clipped to the overlapping frequency range across all uploaded blocks.
• Uploaded blocks are complex-interpolated onto this common frequency axis.

Z0 and renormalisation

• Each uploaded file is renormalised from its file reference impedance (R in the Touchstone header) to the design Z0.
• That design Z0 is also used for Smith-chart normalisation and exports.

Block models

• Bypass: ideal thru (S21=S12=1, S11=S22=0).
• Gain(dB)/Loss(-dB) (positive): ideal matched unilateral amplifier (S21=10^(G/20), S12=0, S11=S22=0).
• Loss (dB) (negative): passive reciprocal attenuator (“pad”). S21=S12=10^(G/20) and a finite per-port return loss is applied (default 30 dB) so reflections are attenuated as they bounce (bench-like behaviour).
• Uploaded .s2p: used as provided (after renormalisation to design Z0).
• Uploaded .s1p (blocks 1 or 7): promoted to a symmetric, reciprocal, lossless 2-port consistent with the supplied S11 magnitude.

Cascade maths

• Each block S-matrix is converted to ABCD at design Z0, multiplied in order, then converted back to S-parameters.

Exports

• CSV: frequency in Hz and S-parameters as mag(dB) and angle(deg).
• .s2p: Touchstone # Hz S DB R Z0 with values in mag(dB) / angle(deg) format.