Saving Trace Data to a File

Other topics about Data Output

Saving Data in CSV Format

The E4991B allows the user to save data for the active trace on the active channel to a CSV file (file extension *.csv) and to load the data into PC application software for further processing.

Trace data are saved in the format shown below.

Example of saved trace data

"# Channel 1"
"# Trace 1"
Frequency, Formatted Data [Ohm], Formatted Data
+1.00000000000E+005, +1.65934825690E+000, +0.00000000000E+000
+1.03514217000E+005, +1.60404013241E+000, +0.00000000000E+000
+1.07151931000E+005, +1.54976894396E+000, +0.00000000000E+000
+1.10917482000E+005, +1.49851693224E+000, +0.00000000000E+000
+1.14815362000E+005, +1.44754297200E+000, +0.00000000000E+000
+1.18850223000E+005, +1.39843292454E+000, +0.00000000000E+000

The first line shows the number of the active channel at the time the data is saved.

The second line shows the number of the active trace at the time the data is saved.

The third line is a header line indicating the contents of each item of trace data written on the fourth line onward.

The fourth line onward shows the trace data. The amount of data is determined by the number of points (frequency) assigned to the trace.

Saving Trace Data

Follow the procedure below to save trace data from the E4991B.

  1. Press Channel Next (or Channel Prev) and Trace Next (or Trace prev) to select the trace to be saved.

  2. Press Save/Recall > Save Trace Data to open the Save As dialog box.

  3. Select the destination folder and input a file name.

  4. Click Save to save the file.

  5. This function is inactive when the security level is set at low/high.

Saving Data in Touchstone Format

You can also save trace data of a E4991B active channel of S-parameter to a Touchstone format file.

Touchstone file data format

You can use data in a touchstone-format file for equivalent circuit analysis and so on using a circuit simulator such as Advanced Design System (ADS). For more information on ADS, refer to the ADS's users manual.

File Structure

In the case of the E4991B, the data array is saved as S parameters of the 1-port model in a touchstone-format file. You can read out the contents of a file with your text editor because they are text data.

You can save data in "log magnitude - angle", "linear magnitude - angle", or "real number - imaginary number."

You can use data saved in Touchstone format for a circuit simulator such as Keysight Advanced Design System (ADS) on your PC (personal computer) or workstation. For more information on the ADS, refer to the operation manual that comes with the system.

Data structure in Touchstone file

Data structure of the Touchstone file consists of a header part and a data part. The contents of the file is text data, which is ready to be read with a general text editor.

The header part consists of the returned value of *IDN?, file created date, calibration state, list of all S parameters of a specified port, and format information.

The header parts of s1p are shown below.

Header of s1p

!Keysight Technologies,E4991B,<ID>,<FW Revision>
!Date <Date>
!Data:
!Freq S11
# Hz S FMT R 50

The option line starting with "#" is placed at the beginning of the file. The structure of the option line is as follows:

Parameter

Description

Hz

Indicates the frequency unit. For the E4991B, it is fixed to Hz.

S

Specifies the type of parameters in data lines. For the E4991B, "S" is specified that indicates the S parameter.

FMT

Specifies the format.  This can be changed by the selection.

RI = Real number - imaginary number
MA = Linear magnitude - angle
DB = Log magnitude - angle

R 50

Specifies the characteristic impedance. For the E4991B specified is "R 50", meaning 50 .

The following figures show the data structures of files saved in Touchstone format.

1-port Touchstone file

 Restrictions when saving data in Touchstone format

2-port Touchstone file

Saving procedure

Follow the steps below to save trace data in Touchstone format.

  1. Press Channel Next  (or Channel Prev) and Trace Next (or Trace prev) to select the trace to be saved.

  2. Press Save/Recall > Save SNP.

  3. Click the softkey that corresponds to the data format you want to save.
     

    Softkey

    Function

    LogMag/Angle

    Select "log magnitude - angle" data format

    LinMag/Angle

    Select "linear magnitude - angle" data format

    Real/Imaginary

    Select "real - imaginary number" data format

  1. Click Save S1P | Save S2P Series | Save S2P Shunt.

  2. Save As dialog box opens. For its operations, use an external keyboard and mouse.

  3. Specify the folder to which the file should be saved, enter a file name, and then press Save to save the file.

  4. When saving data in a sweep process, the data during sweep is saved into a Touchstone file. That is, the previous sweep data is saved as data that has not been swept; or, if sweep was not performed previously, zero data might be saved. Therefore, you should set the active channel to the HOLD state when saving data into a Touchstone file.

  5. This function is inactive when the security level is set at low/high.