Using ECal

This topic discusses all aspects of performing an ECal:

Care and Handling of ECal Modules

You can improve accuracy, repeatability, and avoid costly repair of equipment in the following ways.

Practice proper connector care. See Connector Care.
Protect equipment against ESD damage. Read Electrostatic Discharge Protection.

Power Level into an ECal module

NEVER exceed the following Damage levels to the ECal module.
For highest accuracy, do not exceed the following ECal Compression levels when calibrating:

Model	Compression level	Damage level
N469x series	-5 dBm	+10 dBm
N4432x series N4433x series N443xD series	-7 dBm	+20 dBm
N4431B	+7 dBm	+20 dBm
N755xA series	-15 dBm	+10 dBm
N756xA series	-10 dBm	+15 dBm
8509x series	+9 dBm	+20 dBm

The power level can be increased after calibration with minimal impact on measurement accuracy.

Connect ECal Module to the Analyzer

ECal modules are controlled and powered through a USB connection. When you connect the module, the type of module, frequency range, and connector type are automatically recognized.

For PXI modules, connect the ECal module to a USB port on the remote or embedded controller.

Important Note: DO NOT connect/disconnect USB devices during ECal calibrations. Doing so may cause problems with the calibration.

Notes:

Unused ECal modules that have completed a calibration may remain connected to the USB port.
You can connect and disconnect the ECal module while the analyzer is operating. However, DO NOT connect or disconnect the module while data transfer is in progress. This can result in damage or at least corrupted data.

N756xA ECal Connection

N756xA Multi-port ECal module does not support the auto port orientation but executes the connection check when Do orientation is checked. The following measures must be taken to ensure the calibration is performed properly:

Note: Multiport ECal for PXI Switches application offers more flexible connection setup.

N756xA ECal port must be connected from the port A on the first unit. Do not skip a port on the Ecal.
The VNA port number and N756xA ECal port number must be sequential each other.
In Cal All, the rules are applied on all ports in channels, not each channel. Example: Cal All can execute on the setup (Ch1: port 1/4/7, Ch2: port 2/5/7, Ch3: 3/6/9) in the connection example below.
In the multi-unit configuration, the units must be ordered sequentially by the serial number

"Unable to orient Ecal" is displayed if the Do Orientation is checked and the connection is incorrect.

Connection Example

The serial number of unit 1 should be smaller than the one of unit 2.

Correct Connection Examples

Case 1: Skipping VNA ports is acceptable

Case 2: Use "CAL ALL" instead of Smart Cal or Ecal (under Other Cals) . The Smart Cal and Ecal cannot execute on Channel 2. Because the channel 2 starts from the port C on Ecal.

Incorrect Connection Examples

Case 1: The port C is skipped.

Case 2: The port connection is not sequential.

Case 3: The connection does not start from the port A of unit 1. (In the multi-unit configuration, the units must be ordered sequentially by the serial number.)

How to Perform a Calibration Using ECal

Select an ECal module that has connectors of the same type and gender as the DUT. If such an ECal module is not available, a module with connectors different from the DUT can be used by using Advanced Settings or User Characterization. See Also: Perform a 4-Port Cal with ONE 2-Port ECal Module

Connect the ECal module ports to the analyzer ports. During the calibration process the analyzer can either automatically detect how the ECal module is connected, or the orientation can be performed manually.

Connect the ECal module USB cable to the analyzer USB. See Connect ECal Module to USB.
Allow the module to warm up until it indicates READY.

Note: N755xA series ECal modules do not require a warm-up period.

Enter the analyzer settings. See Set Up Measurements.
Do one of the following to start the Calibration Wizard

Using Hardkey/SoftTab/Softkey

Press Cal > Main > Other Cals > Ecal....

In the Guided Calibration Wizard dialog box (step 2), select ECal option from the Cal Kits combo box.

Select Calibration Ports and ECal Module dialog box help

Allows you to select calibration type and settings.

Cal Type Selection / Configuration Select the number of ports to calibrate. Then select the port number configuration.

4 Port ECal

3 Port ECal

2 Port ECal

1 Port ECal- (Reflection) Advanced Settings are not available.

View/Select ECal Module Click to Select the ECal module if more than one ECal module is connected to the USB. Also, Select the User Characterization within the module. Learn more about User Characterization.

Show Advanced Settings Check to display the Advanced Settings when Next is clicked.

Calibrate source and receiver power Check to perform a Guided Power Calibration. Learn more.

Back Return to Cal Wizard Begin dialog.

Note: ECal isolation is not performed. The inherent isolation of the analyzer is better than that attained with correction using an ECal module.

Note: Terminate any unused ECal ports with a 50 ohm load. Refer to Determining Effects of Not Terminating Unused ECal Ports.

Note: Do not connect any USB memory during ECal calibration.

ECal module not found dialog box help

When this dialog appears, the ECal module is not connected or has not been recognized by the network analyzer.

Retry Check the USB connections and click to continue.

Notes:

If your ECal module is not detected, try to unplug, then reconnect to the USB.
When the ECal module is connected to the network analyzer for the first time, it may take approximately 30 seconds for the analyzer to recognize the module and make it available for calibration.
For best accuracy, allow the ECal module to warm-up until it indicates READY.
See Connect ECal Module to USB.

Select Module and Characterization dialog box help

Note: User Characterizations listed in the dialog below that have no temperature shown cannot be temperature-compensated during calibrations. Also, this is true of CalPod as ECal characterizations that were performed prior to this temperature capability in the VNA firmware, because temperature was not measured-and-recorded. However, the firmware will still recognize those and allow them to be used for cals.

ECal Module Select one of the ECal modules that are connected to the analyzer.

Detect Connected ECals Click to rescan the USB for ECal modules.

Available Characterizations

ECal Module Memory - Displays the factory and user characterizations that are stored in the ECal module.

Instrument Disk Memory - Displays the user characterizations that are stored in Disk Memory. Learn more User Characterizations in Disk Memory.

Temperature - Displays the temperature reading at the time a characterization was performed.

The information in the Calset Properties dialog confirms which of those characterizations were temperature-compensated during calibration. The (compensated) notation for a CalPod indicates that the CalPod’s characterization was temperature-compensated when that cal’s error terms were computed (it also implies the factory thermal data for that CalPod must be present on the VNA). Whereas the (uncompensated) notation indicates that temperature-compensation could not be done for that characterization during the cal, which could mean either that one is an older characterization that didn’t record its temperature, or else factory thermal data for that CalPod serial # was not installed on the VNA.

Select the characterization data to use for the calibration. Once selected, that characterization becomes the default selection until the analyzer is turned OFF and restarted. When restarted, Factory again becomes the default selection.

Error: Frequency Range dialog box help

When this dialog appears, the current cal standards (or ECAL module) does not cover the current frequency range of the measurement. Do one of the following to correct the problem:

Cal Kit Class Category Not available with ECal modules.

Frequency Change the frequency range of the active channel.

Edit Not available with ECal modules.

Back Select a different characterization that covers the required frequency range.

Cancel Re-characterize the module with an increased frequency range.

Select DUT Connectors and Cal Kits dialog box help

If the ECal module or selected User Characterization has more than one connector type, then the following dialog box is presented which allows you to describe the DUT connector type. Otherwise, click next to proceed to Advanced Settings (if checked) or ECal Steps.

Connectors

The available connectors are listed for each DUT port.

Advanced Settings dialog box help

Thru #n

Lists the proposed Thru connections to be made during the calibration process. You can change these Thru connections to better suit your test setup.

The proposed Thru connections are listed automatically.
Additional Thru connections can be selected for higher accuracy. Learn more.
For Balanced measurements, learn which Thru paths to select.

Add Thru

Click to add a Thru connection. Learn more

Remove Thru

Select a Thru by clicking the "Thru #N" field or the "1st Port / 2nd Port" field. Then click "Remove Thru". This selection is NOT available if the selected Thru is required for the calibration.

1st Port / 2nd Port

Click to change the two ports to be included in the Thru connection. The order of the port numbers (1st or 2nd) is not critical.

Thru Cal Method

Lists the available Thru Cal methods for the specified port pairs.

Learn about ECal Thru Methods

Cal Type/ Stds

Click to invoke the View / Modify Properties of Cal dialog box

Do orientation

When this box is checked (the default setting) the VNA automatically senses the model and direction in which an ECal module port is connected to the VNA ports. If power to the ECal module is too low, it will appear as if there is no ECal module connected. If you use low power and are having this problem, clear this check box to provide the orientation manually.

Orientation occurs first at the middle of the frequency range that you are calibrating. If a signal is not detected, it tries again at the lowest frequency in the range.

Note: The orientation is not supported but the connection check is done for the N756xA Multi-port ECal.

Choose delta match

Available only when a Delta Match Cal is required.

Check, then click Next to invoke the Select Cal Set for Delta Match dialog box.
Clear - The Cal Wizard uses the Global Delta Match Cal if available.

Specify how the ECal module is connected dialog box help

This dialog box appears when the Do orientation checkbox in the previous dialog box is cleared.

Click the ECal Port that is connected to each VNA port.

Electronic Calibration Steps dialog box help

Note: Beginning in VNA Rev. 6.0, ECal can be performed with External triggers. Learn more.

Displays the instructions for each measurement required for calibration.

Measure Measures the ECal standards.

Done Click when last standard has been measured.

Saving an ECal Calibration

When complete, you can save the new calibration. Learn how.