Setting Up, Calibrating, and Making Measurements using the TDR-Based PLTS

This topic guides you through the following:

• Overview

• Starting the Startup Wizard

• TDR Setup

• Select the Calibration and Measurement Parameters

• Calibration

• • Calibration Kit Selection

  • Calibration Kit Definition

  • Perform Calibration

• Making a Measurement

• • Device Under Test Connection

  • Initial Analysis Type Selection

  • Modify the Measurement Stimulus and Parameters

  • Running a Measurement

Overview

PLTS supports the TDR-based PLTS hardware using coaxial test cables. You will need four coaxial test cables for the TDR-based PLTS measurements.

For the Keysight DCA 86100A/B/C, we recommend you use:

• Four 3.5 mm (male-female) cables (such as the Keysight N4419A-B20) -OR-

• Four 3.5 mm (male-male) cables (Keysight part number 8120-4948) with a 3.5 mm (female-female) adapter used as a connector saver

For the Tektronix CSA8000 and TDS8000, we recommend you use:

• Four 3.5 mm (male-male) cables (Keysight part number 8120-4948) -OR-

• Four 3.5 mm (male-female) cables (such as the Keysight N4419A-B20) with a 3.5 mm (male-male) adapter (Keysight part number 1250-1748)

You also need the following calibration standards to perform the TDR calibration. Different standards are required depending on the TDR-based PLTS hardware and the desired calibration type.

Required 3.5mm (SMA) Calibration Standards

Recommended Keysight Part Numbers:

• Loads, 3.5mm (f), 1250-2151; 3.5 mm (m) 1810-0118

• Shorts, 3.5mm (f), 1250-2152; 3.5mm (m) 1250-2153

• Thrus, 3.5mm (f-f), 5061-5311;

Keysight Probe Model Numbers:

•  N1020A 6 GHz Time Domain Reflectometry Probes (Set of 4)

•  N1020A-K05 Calibration Substrate for use with N1020A Probes  

Launching the Startup Wizard

The Startup Wizard is displayed when the PLTS application is started.  It is also displayed anytime a new measurement is initiated, such as after selecting New from the File menu, or clicking on the new file icon on the toolbar. Learn more about the Startup Wizard.

Set Up the TDR

This dialog box allows you to set the TDR parameters for the calibration and measurement. Each of these parameters is described in the following table TDR Parameter Descriptions.

This wizard screen is initially displayed with default values for each entry. You may accept or modify these values. Modifying some of these values directly may also modify other associated values interactively. For example, when changing the Effective Dielectric Constant, the Relative Velocity Factor will change appropriately.

Reset Values  returns all selections and values to their default value.

TDR Parameter Descriptions

When the Setup TDR dialog box values are correct, click Next > to continue.

Select the Calibration and Measurement Parameters

The Select Calibration and Measurement Parameters dialog box is displayed. The left side of the dialog box lists all 16 of the available single-ended measurements. The right side of the dialog box lists all 16 of the available differential measurements.

When a measurement is selected, it has a check in the check box for the corresponding measurement. However, you may not need or desire data for all 32 parameters (16 single-ended and 16 differential parameters). As a general rule, the more parameters that you select, the longer the calibration and the measurement takes to perform.  The following provides a tool for estimating calibration times for each selected parameter.

Approximate Calibration Times for Single-Ended Parameters

Leave all parameters selected for this example exercise and then click the Next > button.

Performing a Calibration

The PLTS software adds value and capability to both Keysight and Tektronix TDR systems by automating the calibration process which saves time, reduces the chance of calibration errors, eliminates tedious procedures, and improves the calibration results. The PLTS calibration process includes:

1. Selecting a calibration kit and defining the calibration file name.  This step uses the Select Calibration Kit and Filename dialog box to select the calibration standards and connectors that are used during the calibration process. The file name that the calibration information is saved to is also defined.

2. Defining a calibration kit.  This optional step allows you to define a calibration kit if none of the pre-defined calibration kits match your calibration needs.

3. Choosing the calibration type.  This step uses the Calibrate TDR and Modules wizard window to define the type of TDR calibration that will be performed, either a "Reference Plane Calibration Only" or a "Normalization and Reference Plane Calibration".

4. Performing the calibration for the TDR modules. This step uses the Calibrate TDR and Modules wizard window to perform the calibration for the modules within your system.

5. Setting the reference plane at the end of the cables. This step uses the Calibrate TDR and Modules wizard window to perform the standards calibrations, either the Reference Plane Calibration Only or the Normalization and Reference Plane Calibration.

Once the Next > button in the Select Calibration and Measurement Parameters dialog box is selected, the Select Calibration Kit and Filename wizard screen is displayed.

Note: At any time you can initiate a re-calibration of  your measurement hardware, Characterize an Adapter, or Edit a Cal Kit. Select Utilities, then select your hardware setup.

Select a Calibration Kit and Define the Calibration File Name

The PLTS software has five default TDR calibration kits. It also stores the calibration kit information.

Pre-Defined TDR Calibration Kits

1. Select the calibration kit to use: The PLTS software has several calibration kits already defined for the TDR calibration. All of these calibration kits are listed in the Select the calibration kit to use: list. PLTS is set to the Default 3.5mm selection.

If the calibration kits listed in the Select the calibration kit to use: list area do not match your calibration kit, you may define a new calibration kit to meet your requirements. Refer to Define a Calibration Kit.

2. Specify calibration file to create/modify: Specify the file that you will use to save the calibration data.  The text box displays a default calibration file name based on the current date. It uses the string "TDRcal_" followed by the current date. You may enter another file name if you like. This calibration file name is used as a base name for saving calibration files on the PC and on the Keysight 86100-based TDR (if this TDR is being used).

• Files Stored on the PC   This calibration file name is used as a base name for saving calibration files on the PC for the TDR. The calibration will be saved to the calibration directory. If you installed PLTS to the default C:/ directory, you may follow this path to the calibration directory: C:/Program Files/Keysight/PLTS/calibration

• Files Stored on the 86100-based TDR   This calibration file name is also used as a base name to store additional calibration and setup files if you are using an Keysight 86100A/B/C TDR. The files stored on the 86100-based TDR are dependent on the calibration and measurement parameters that you selected in the initial setup procedure. For each parameter calibration, a setup file and a calibration file are stored on the 86100 hard drive in the "setups" directory and the "TDR normalization" directory, respectively.

If you want to overwrite a previously saved calibration file, you may select the Load button to display the TDR Calibration Files Found dialog box. The dialog box displays each TDR calibration file that has been saved in the Existing Calibration Files list.

You may review the calibration data that is saved in a calibration file by selecting a file in the Existing Calibration Files list. When a file is selected, its calibration information is displayed in the Selected Calibration File Information area.

Calibration files may be deleted by selecting the calibration kit in the Existing Calibration Files list and then selecting the Delete Cal File button. This also deletes the corresponding normalization files on the 86100-based TDR.

Note: Normalization files are stored on the Keysight 86100 DCA mainframe drive.

Click the OK button to return to the Select Calibration Kit and Filename wizard screen.

3. After the calibration kit is selected and the calibration file name is defined, click the Next > button to continue with the calibration.

For this example, the selected calibration kit is set to the Default 3.5mm selection and the default calibration file name.

Define a Calibration Kit

If none of the previously defined calibration kits in the Select the calibration kit to use: list meets your requirements, you can define your calibration kit. To define a calibration kit:

1. Exit the startup wizard by clicking the close button in the upper right corner of the wizard: If you exit the wizard, all previously-defined setup definitions are lost.

2. From the Utilities menu, select the TDR System Model (in this case, 86100A|54754A|54754A), then click Edit Cal Kits .

3. In the Select Cal Kit dialog box, make sure 4-Channel TDR is selected in the Select Calibration Type list, then select the USER_DEF selection and click Edit to start the process.

4. The calibration kit definition is performed in the Edit TDR Calibration Kit dialog box. Enter Cal Kit ID and Name into the appropriate entry boxes in the header.  The Cal Kit ID is listed in the Cal Kit column and Name is listed in the Description column of the calibration kit selection window.

5. Also enter Connector Type. You may optionally specify the minimum (Min. Freq. MHz) and the maximum (Max. Freq. MHz) frequencies in megahertz.  The PLTS software does not currently use the frequency range information.

6. Enter the delay values for the open and short standards Open Delay and Short Delay entry boxes. Enter the delay values in picoseconds. The value may be found in the calibration kit documentation if you are using a standard from a calibration kit.  Typically, if you are using an un-terminated connector or cable as the open, you may enter "0" (zero) ps as the value for the open.

7. Enter the delay value (in picoseconds) of the thru in the Thru Delay entry box. Then, in the list of thrus, select the box at the left of the thru and click the Add button to associate the thru to the entered delay value. Repeat this until all six thru paths are completed.

The color of the box at the left of the thru changes from red to green as the thru path is completed. Be sure to enter a delay value for all six thru paths.

If your thru is part of an Keysight (or Hewlett-Packard) calibration kit, the delay value is listed in the Standard Definitions section of the calibration kit documentation.

The Remove button disassociates the delay value with the thru path allowing you to change the delay value for the path.

All of the thru paths may use the same delay value or you may have multiple thru delay values if you are using a thru having a different delay. One instance of using more than one delay value might be when you are creating a calibration kit definition for probing and not all of the thru paths would use the same thru delay value.

8. After the Edit TDR Calibration Kit dialog box is complete, click the OK button to save the calibration kit with the new information and return to the Select Cal Kit dialog box shown in displaying the newly defined calibration kit in the list. Cancel deletes the information entered and returns to the Select Cal Kit dialog box.

9. Then click the Close button to close the  dialog box.

Return to the Startup Wizard by selecting New from the File menu to make your measurement. Refer back to Starting the Startup Wizard.

Calibrate TDR and Modules

After selecting the calibration kit, verifying the data file, and selecting the Next > button, the Calibrate TDR and Modules wizard window is displayed.  This wizard window is used for the entire calibration.

1. Choose Cal. Type

Ref. Plane Calibration Only:

• Available to ALL supported TDR systems.

• Adjusts the reference plane at the end of the cables. Does NOT compensate for loss in the cables.

• Automatically de-skews the cables when differential measurements are selected.

• Positions the trace on the display for easy viewing.

• Recommends the module calibration.

Normalization & Ref. Plane Calibration:

• Available ONLY with the Keysight 86100-based TDR system using the 86100's built-in differential TDR/TDT normalization feature.

• Has all of the features as the reference plane calibration selection listed above.

• Is the most complete and accurate TDR calibration.

• Removes cable loss, mismatch, and reflection errors which can be significant.

• Requires the module calibration.

2. Module Cal (also called the vertical channel calibration)

• Calibrates the module gains, offsets, and timing for each channel.

• Available to all supported TDR systems.

"L" represents the left module (channels 1 and 2)

"R" represents the right module (channels 3 and 4).

A text box indicates the status of the module calibration. The module calibration is NOT always required.  The color of the module calibration icon also shows the status of the module calibration.

• Red -  REQUIRED

• Yellow -  RECOMMENDED

• Green -  VALID.

Requirements for Module calibration vary between the Tektronix and Keysight instruments. In general, the Tektronix instruments rarely requires you to calibrate. The Keysight instruments require module calibration when any of the following are true:

• Performing Normalization & Ref. Plane Calibration:

• The instrument power has been cycled.

• The module has been removed and then reinserted.

• The ambient temperature changes more than 5C since the last module calibration

Resistance Value - Allows you to enter the resistance value of your load. The default value is 50 ohms.

How to Perform a Module Calibration

1. Enter the resistance value of your load in the Resistance Value text box if it varies from the current value.

2. Click the L icon to start the module calibration.

3. Follow the PLTS prompts to perform the module calibration for the left module. When the module calibration is complete, the L icon color changes to green.

4. Repeat steps 2 and 3 to perform the Right module calibration.

The module calibration procedure is now complete and the module calibration factors are stored in the non-volatile memory in the modules.

CAUTION   If either of the module calibrations fail, you may still be able to complete the calibration and make a measurement. However, the accuracy of the measurement will be in doubt. It is recommended that you reattempt the module calibration before proceeding and correct the equipment problem, if there is one.

3. Connect Standards

This procedure does the following:

1. Sets the reference plane at the end of the cables.

2. Automatically de-skews the cables if differential measurements are selected.

3. Performs normalization (if Normalization & Ref. Plane Calibration is selected) which removes cable loss, mismatch, and reflection errors.

Automatic De-Skewing

• Unmatched cables and differences in the path of the TDR module cause skew in differential and common signals.

• Skew must be removed to provide accurate differential measurements.

• De-skewing is required for Reflection and Transmission measurements.

• PLTS removes the reflection skew by measuring the amount of skew, and then adding 1/2 of the amount to the appropriate channel. PLTS then repeats the process, iteratively adjusting the channels until the rest of the skew is removed.

• After reflection is de-skewed, thrus are used to connect Channel 1 to channel 3 while channel 2 is connected to channel 4. The time difference is measured in the two TDT signal paths and de-skewing is applied to the appropriate channel correcting the transmission response.

• PLTS can remove skew of up to 780 ps in the Keysight TDR system and of up to 340 ps in the Tektronix TDR systems.

The icons that are displayed depend on the calibration and measurement parameters that are selected during the initial setup in Select the Calibration and Measurement Parameters. The following shows when each of these icons are displayed and which calibrations are required based on the selected parameters.

For all Icons the color indicates the state of completion:

• RED - Cal Needed

• BLUE - Cal in Process

• GREEN - Cal Complete

Reflection Paths for Single-Ended, Differential-Mode, and Common-Mode Calibration Parameters

Thru Paths Required by the Parameters Selected

The transmission parameters are calibrated using thru connections at the ends of the cables. Some of these thru path icons may not be displayed when you are performing a calibration. As with the reflection icons shown above, the icons that are displayed depend on the calibration and measurement parameters that are selected during the initial setup in Select the Calibration and Measurement Parameters. The following table also shows when each of these icons are displayed and which calibrations are required based on the selected parameters.

1 When a differential parameter warrants the thru path calibration on either thru path 1 - 3 or 2 - 4, the calibration of the other thru path is required and is performed at the same time.

How to Connect Cal Standards to Perform the Calibration

• Click a RED icon in the Connect Cal Standards area to start the calibration.

• You may click the icons in any order.

• Follow the PLTS software prompts on your PC rather than following any prompts that is displayed on your TDR instrument.

• TDR icons represent RELFECTION parameters; TDT represents TRANSMISSION parameters.

• Continue until all icons are GREEN.

• You can re-calibrate any parameter if you suspect there is an error. Select the GREEN icon that represents the suspect parameter and follow the prompts.

• Click Next > to complete the calibration.

Making a Measurement

The Measurement process includes:

1. Connect the DUT  This step shows you how to connect your DUT to the PLTS.

2. Select the initial displayed format of the measurement  This step guides you through selecting which of the ten analysis formats that the upcoming measurement will initially be displayed in. The measurement can be displayed in any of the 10 formats at any time.

3. Modify the measurement stimulus and measured parameters  This optional step allows you to make last minute changes to the measurement stimulus dialog box and the measurement parameter dialog box. Only changes that will not require a recalibration may be made.

4. Run the measurement  This step guides you through starting the measurement and displaying the data when the measurement is complete. It also directs you to save the measurement and points you to the chapters that will assist in your data analysis.

Connect the DUT

1. After saving the calibration data and selecting the Next > button, the Device connection scheme for TDR calibrations window is displayed. This wizard window shows how to connect your DUT to the TDR system to make the measurement. Connect the DUT to the TDR system as shown and then click the Next > button.

Select the Initial Displayed Format of the Measurement

1. The Hardware and Calibration Setup Wizard Complete window is displayed.

This window is the software location to select the one of ten analysis formats that the measurement will be displayed as initially. The analysis formats are:

Note: Your PLTS application may not include the optional RLCG analysis feature.

For the purpose of this example, the Time Domain (Differential) format icon is selected.

Modify the Measurement Stimulus and Measured Parameters

1. The Modify Measurement Stimulus button opens the Measurement Stimulus dialog box. This dialog box allows you to change some of the measurement stimulus settings that you set up previously.

Settings that would require a recalibration are not active and may not be changed in this dialog box. To change the stimulus settings that are inactive, you must click the < Back button until you get back to the window described in Set Up the TDR.

For the purpose of this example, leave the settings unchanged and click the OK button.

The Reset Values button resets any active values (any values that can be changed without requiring a recalibration) to their original default values prior to being changed in To Set Up the TDR.

The Cancel button resets any changes that were made after opening this dialog box.

Note: After the measurement has been made, you may verify these changes were made by printing a characterization report. See Characterization Report Generator for help.

2. Once you exit the Measurement Stimulus dialog box, the Select Measurement Parameters dialog box is displayed. The left side of the dialog box lists all 16 of the TDR single-ended measurements. As with the dialog box described in Select the Calibration and Measurement Parameters, the right side of the dialog box lists all 16 of the TDR differential measurements. Only the parameters for which the calibration is valid are active. You may select all of the active parameters or you may select a subset of these parameters. Selecting a subset of the parameters may save you some measurement time.

Note: Beginning with PLTS Rev 5.0, when ONLY Balanced parameters are measured, PLTS can recalculate the Single-Ended S-parameters if enough Balanced data is measured. To do this, Import the Balanced measurements, then Export the Single-Ended parameters.

To measure parameters that are inactive, you must click the < Back button until you get back to the window shown in Select the Calibration and Measurement Parameters and reselect the parameters. However, note that if you change the parameters in this window, you may be required to perform additional portions of the calibration.

For the purpose of this example, leave the parameters unchanged and click the OK button.

3. With the Hardware and Calibration Setup Wizard Complete window is displayed, select the Next > button to start the measurement.

Run the Measurement

1. The software displays the wizard's Measurement & Post-Processing Status window and starts the measurement and the measurement post-processing. The software makes each of the measurements. The status of the measurements and the post-processing is displayed in the status text area. The status may also be observed by watching the status bar at the right edge of the text area. As the measurements and the post-processing proceed, the color of the bar gradually changes to blue.

Once the post-processing is complete, click the Next > button to display the measurement results in the main PLTS window.

Analyzing the Measurement Results

Now that the measurement has been made, the main Physical Layer Test System (PLTS) window gives you the flexibility to perform analysis on the measured data in a variety of ways. Learn more.

CAUTION   To ensure the measurement data is not lost, save the measurement data by clicking File, then Save.