SnP (Touchstone) File Format

PLTS can import and export SnP files (*.s1p, *.s2p, *.s3p. and so forth). The SnP data file format is also known as Touchstone format.

This file format is used by CAE programs such as:

Beginning with PLTS 2012, Touchstone 2.0 files can be imported and exported. Learn more.

Both Touchstone 1.0 and Touchstone 2.0 files contain S-parameters that describe frequency-dependent linear networks.

The difference between *.s1p, *.s2p, *.s3p, (and so forth) files is the number of ports involved in the measurement, and therefore, the number of S-parameters that are saved.

File Type

# of Ports

# of S-parameters saved



1 S-parameter



4 S-parameters



9 S-parameters



16 S-parameters



N2 parameters

SnP (Touchstone1) Data

SnP files contain header information, stimulus data, a response data pair for EACH data point. There can be up to 16,000 data points (records) in each file.

The following is a sample of Header information:

! is a commented line.

!Keysight Technologies,E8362B,US42340026,Q.03.54

!Keysight E8362B: Q.03.54

!Date: Friday, April 25, 2003 13:46:41

!Correction: S11(Full 2 Port SOLT,1,2) S21(Full 2 Port SOLT,1,2) S12(Full 2 Port SOLT,1,2) S22(Full 2 Port SOLT,1,2)

!S2P File: Measurements:S11,S21,S12,S22:  

# Hz  S RI R 50

Note: Although the following shows Real / Imag pairs, the format could also be LogMag / Phase or LinMag / Phase

Time Domain touchstone file format is similar to frequency domain touchstone except the x-axis unit is time (s, ns) instead of frequency (Hz, MHz).

Each record is a data point. There can be up to 16,000 data points (records) in each file.

*.s1p Files

Each record contains 1 stimulus value and 1 S-parameter (total of 3 values).

Stim  Real (Sxx)  Imag(Sxx)

*.s2p Files

Each record contains 1 stimulus value and 4 S-parameters (total of 9 values)

Stim  Real (S11)  Imag(S11)  Real(S21)  Imag(S21)  Real(S12)  Imag(S12)  Real(S22)  Imag(S22)

*.s3p Files

Each record contains 1 stimulus value and 9 S-parameters (total of 19 values)

Stim   Real (S11)  Imag(S11)  Real(S12)  Imag(S12)  Real(S13)  Imag(S13)

          Real (S21)  Imag(S21)  Real(S22)  Imag(S22)  Real(S23)  Imag(S23)

          Real (S31)  Imag(S31)  Real(S32)  Imag(S32)  Real(S33)  Imag(S33)

*.s4p Files

Each record contains 1 stimulus value and 16 S-parameters (total of 33 values)

Stim   Real (S11)  Imag(S11)  Real(S12)  Imag(S12)  Real(S13)  Imag(S13)  Real(S14)  Imag(S14)

          Real (S21)  Imag(S21)  Real(S22)  Imag(S22)  Real(S23)  Imag(S23)  Real(S24)  Imag(S24)

          Real (S31)  Imag(S31)  Real(S32)  Imag(S32)  Real(S33)  Imag(S33)  Real(S34)  Imag(S34)

          Real (S41)  Imag(S41)  Real(S42)  Imag(S42)  Real(S43)  Imag(S43)  Real(S44)  Imag(S44)

This pattern continues for N ports involved in the measurement.

Touchstone 2.0 Data Files

Touchstone 2.0 has specifications for saving Mixed-mode (Balanced) S-parameters. When Touchstone 2.0 is selected in PLTS from the Import and Export dialogs, data are saved to *.ts files.

The format is slightly different from Touchstone 1.0 files as shown in the following partial image of an *.ts file.

Touchstone 2.0 has the ability to save data with different reference impedance for each port, indicated by [Reference] in the above image. However, currently PLTS does NOT have the ability to measure data into different impedances for each port.

TDA Systems MeasureXtractor

PLTS exports 4-port S-parameters in Touchstone format for import into TDA Systems' MeasureXtractor. This is a powerful capability that allows you to describe the exact frequency dependent behavior of your passive device using an S-parameter block inside of MeasureXtractor. MeasureXtractor also allows you to create a SPICE compatible model for further circuit simulation.

Access the PLTS Æ TDA MeasureXtractor export feature by selecting Export then TDA MeasureXtractor from the File menu.

File Format and Port Conventions

The format of the 4-port S-parameter Touchstone file is magnitude (in dB) and phase (in degrees) information at each frequency point. Port designations in the resultant Touchstone file are as they appear in the DUT file.

Requirement when S-Parameter Blocks are Cascaded

Recommendations for a Good MeasureXtractor-compatible File

Recommendations for Using the Exported File in MeasureXtractor

In TDA Systems' software:

See other File and Print Operations topics