Online S2P and Touchstone File Viewer
Drop a Touchstone file (.s1p, .s2p, .s3p, .s4p) onto the viewer to plot it as magnitude, phase, VSWR, group delay or on a Smith chart. The file is processed in your browser and never uploaded.
Drop an S-parameter file here (.s1p, .s2p, .s3p, .s4p …) or
The file is read in your browser. It is not uploaded anywhere.
No file at hand? Try a sample: · ·
How to use the viewer
- Load a file. Drop it onto the box, or choose it with the button. If you have no file at hand, load one of the three samples. They are generated from ideal circuit models, so no measured or proprietary data is involved.
- Pick the plot. Magnitude in dB is the default. Phase, VSWR, group delay and the Smith chart are in the list. Use the logarithmic frequency axis for wide sweeps.
- Pick the traces. S11 and S21 are on by default. Switch the others on to compare, for example S11 with S22, or S21 with S12 to check reciprocity.
- Read values. Move the pointer over the plot, or press the left and right arrow keys when the plot has the keyboard focus, and the table below the plot shows the frequency with the magnitude, phase and VSWR of every trace.
- Export. Download the selected traces as CSV for a spreadsheet or a script.
What the viewer shows
- Magnitude (dB): 20·log10 of the S-parameter magnitude. For S11 and S22 this is the negative of the return loss, for S21 and S12 it is the gain or the insertion loss.
- Phase (degrees): the angle of each S-parameter, wrapped to ±180°, with an option to unwrap it.
- VSWR: computed from the reflection terms (S11, S22 …). Values above 20 are drawn at 20. Use the VSWR and return loss calculator to convert single values.
- Group delay: the negative slope of the unwrapped phase against angular frequency, in nanoseconds. It is meaningful for transmission terms such as S21 and noisy when the phase is noisy or the frequency step is large.
- Smith chart: the reflection coefficient of the selected reflection terms on a Smith chart normalized to the reference impedance of the file, with the lowest frequency marked.
Above the plot the viewer summarizes the file (number of ports, points, frequency range, reference impedance and number format) and lists anything it had to assume or skip. For one-port and two-port files it also reports whether the device is passive. That check uses the largest singular value of the S matrix: for a passive device it must not exceed 1, apart from measurement error. A reading above 1 is normal for an amplifier and a warning sign for a filter or a cable.
Limits
This is a viewer for a quick look, not an analysis suite. It does not de-embed a fixture, renormalize to another reference impedance, save markers, compare several files at once or convert between formats. Large files are limited to 25 MB. Files with more than four ports show only the first four ports as traces. For those jobs, use RF View (Windows and Android) or a scripting tool such as scikit-rf.
For how the file format works, the column order of two-port files and the problems you may meet, read the guide how to open an S2P file.
Privacy
The viewer is client-side code. When you load a file, your browser reads it from your disk and does all the processing locally. Nothing is sent to a server, and the file is gone when you close or reload the page. The only data the site collects about the use of the tool is an anonymous usage count (a "calculator used" event) if you accepted analytics cookies.
Related pages on RF View
Guides
- S-parameters overview
- S11 and return loss
- How to batch process SNP files
- How to compare S-parameter files
Tools
Frequently asked questions
Does the viewer upload my file?
No. The file is read and plotted by your browser. It is not sent to this website or to any other server.
Which files can it open?
Touchstone files with S-parameters from one to four ports (and the first four ports of larger files), in RI, MA or DB format and Hz, kHz, MHz or GHz units. It reads version 1 files and the common subset of version 2.0. Files with Y, Z, H or G parameters, mixed-mode data or triangular matrices are refused with a clear message.
How large can the file be?
Files up to 25 MB are accepted, which is far more than a typical measurement file. Very dense sweeps with hundreds of thousands of points may plot slowly on an older computer.
Can I save what I see?
You can download the selected traces as a CSV file with the frequency in hertz and the magnitude in dB and the phase in degrees for each trace. For marker tables, comparisons and reports use RF View.