VMC Measurements

Important Note: Connecting your DUT to the VNA:

RF and IF terminology is NOT used in FCA because the VNA does not know how the DUT is labeled or how it will be used. Instead, the general terms INPUT and OUTPUT are used.

• INPUT - The DUT port being stimulated with frequencies before conversion.

• OUTPUT - The DUT port outputting converted frequencies.

INPUT and OUTPUT Frequencies are specified using the Mixer Setup dialog box.

How to start the VMC Mixer Setup dialog

Using Hardkey/SoftTab/Softkey

Using a mouse

1. Press Freq > Main > VMC Setup... > Mixer Setup tab.

1. Click Stimulus

2. Select Sweep

3. Select VMC Setup...

4. Select Mixer Setup

• Calibration Setup

• • Waveguide/In-fixture/On-Wafer Setup

• Calibration Mixer Characterization

• Measurement Direction

• Select DUT Connectors and Cal Kits

• • Modify Frequency Cal

  • Specify how the ECal module is connected

  • Modify Mixer Cal

  • Select the ECal Port to be connected to the Output of the Calibration Mixer

• Vector Mixer Cal Steps

• Measure Calibration Standards

• • Save Mixer Characterization

• Calibration Completed

• Specify Adapter Delay

How to Perform a VMC Calibration

1. Create an FCA measurement, then...

Using Hardkey/SoftTab/Softkey

Using a mouse

1. Press Cal > Main > Smart Cal....

1. Click Response

2. Select Cal

3. Select Smart Cal...

To perform Mixer Characterization ONLY

1. Press Cal > Main > Other Cals > Mixer Char Wizard....

1. Click response

2. Select Cal

3. Select Other Cals

4. Select Mixer Char Wizard...

Calibration Setup dialog box help

Waveguide/In-fixture/On-Wafer Setup  Check to embed or de-embed circuit networks on the input and output of your mixer under test. Starts the following dialog box.

Additional Power Cal Steps

Enable LO1 / LO2 Power Cal  Check when LO1 / LO2 is controlled (on the Mixer Setup tab) to perform a Power Cal on the LO source(s).

Waveguide/In-fixture/On-Wafer Setup dialog box help

This dialog box appears ONLY if you checked the Waveguide/In-fixture/On-Wafer Setup box in the previous Cal Setup dialog.

Allows you to embed or de-embed circuit networks on the input and output of your mixer under test.

For Network1 (Input) and Network2 (Output) select Embed, De-embed, or None.

Browse  Click to navigate to the .S2P file that models the network to embed or de-embed.

Reverse port positions for input/output  Check to cause the Fixture/Adapter to be configured with Port 2 connected to the VNA and Port 1 to be connected to the DUT. The image in the dialog is updated to reflect that change.

Enable Extrapolation  Check (default setting) to apply a simple extrapolation when the S2P file has a narrower frequency range than the channel. The values for the first and last data points are extended in either direction to cover the frequency range of the measurement. A warning message is also displayed when extrapolation is necessary.

To Embed or De-embed

• When you have a 2 port network that needs to be connected between the Cal reference plane and the DUT during the measurement, but it is NOT present during the calibration, then that network has to be De-Embedded from the port in question during the calibration. In other words, De-Embedding in FCA calibration extends the calibration reference plane to include the two port network.

• When you have a 2 port network that is included as part of the calibration reference plane but has to be disconnected during the measurement, then that 2-port network has to be Embedded for the port in question during the calibration. In other words, Embedding in FCA calibration retracts the calibration reference plane to exclude the two port network during the measurement.

Calibration Mixer Characterization dialog box help

What is Calibration Mixer Characterization? For a brief explanation, see Calibration Mixer.

Select Mixer Characterization Method

Perform Characterization (requires a reference mixer)  Performs a Mixer characterization in addition to the VMC calibration. The mixer characterization file will be saved at the end for use in subsequent VMC calibrations. Choose this selection if you do NOT already have a mixer characterization file to load.

Load characterization from file  Loads an S2P calibration mixer characterization file. Click Browse to locate the file.

Note: Load an *.S2PX file for SEGMENTED VMC measurements. Learn more.

• The frequency range of the S2P file MUST be the same, or larger than, the frequency range of the FCA measurement. If the S2P file frequency range is larger, or the data points do not exactly match those of the measurement, interpolation will be performed.

• The VMC calibration requires that the calibration mixer be connected in the same orientation as that in which it was characterized. The direction in which it was characterized is not part of the file that is recalled. You have to remember and connect it appropriately.

"Invalid Mixer Characterization File" is displayed if the frequency range of the S2P file is smaller that those of the measurement.

Note: A Mixer Characterization Cal can be performed separately. Learn how.

Measurement Direction dialog box help

This dialog box appears ONLY if your settings in the Mixer Setup dialog box indicate that your DUT is being tested as an upconverter (input < output). It allows you to characterize the Calibration Mixer / Filter as a downconverter (input > output) or an upconverter.

The following example shows why you would choose to characterize the calibration mixer as a downconverter. Consider a DUT being used as an upconverter. The input frequency is 70 MHz, the LO is 20 GHz, and the selected (+) output frequency is 20.07 GHz. If we chose (-) in the mixer setup dialog, the output frequency would be 19.93 GHz.

• Characterize as upconverter  A very sharp cutoff filter is required to reject the undesired output of 19.93 GHz and pass the desired 20.07 GHz.

• Characterize as downconverter  The input frequency is 20.07 GHz; the LO is 20 GHz. The sum (+) output is 40.07 GHz and the diff (-) output is 70 MHz. These are very easy to separate with a low-pass filter. The original frequencies are always used in the downconversion process, so be sure to choose a filter that will pass 70 MHz and reject 40.07 GHz.

See connection diagrams.

Select DUT Connectors and Cal Kits dialog box help

Allows you to specify the connector type and Cal Kit for each DUT port.

Port n  For each listed VNA port, specify the DUT connector type and gender, and the Cal Kit to use.

Mixer Out Port  Output port of the image filter that is connected to the calibration mixer. Specify the Cal Kit / standards to use for the measurement of the calibration mixer / filter combination.

Note:  When selecting a cal kit for the Mixer Out Port, be sure that the kit has standards with connectors that can mate to the mixer output port.  If you choose an ECal, the ECal must have at least one port that can mate to the mixer output port.

Note: If your DUT connectors are:

• Waveguide  Change the system impedance to 1 ohm before performing a calibration. See Setting System Impedance.

• Not listed (male and female)   Select Type A as the connector type. Type A requires a calibration kit file containing the electrical properties of the standards used for calibration (see Calibration kits).

• Unspecified (like a packaged device)  Select Type B as the connector type. Type B requires a calibration kit file containing the electrical properties of the standards used for calibration (see Calibration kits).

Modify Cal  Check to start the Modify Cal dialog. If performing a Mixer Characterization Cal at the same time as VMC Cal, two Modify Cal dialogs will be presented, one after the other.

Modify Frequency Cal dialog box help

For VMC calibrations - NOT for Mixer Characterization.

Thru Cal Method  For each Thru connection, choose the Thru method. Learn more about these choices.

Cal Type/Stds  Click to start the Modify Calibration Selections dialog box.

The following selections are available ONLY if using an ECal module.

Do orientation   When this box is checked (default) the VNA senses the ECal model and direction in which the 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.

View/Detect ECal Characterizations  Appears only if an ECal module is selected for use. Click to invoke the View ECal Modules and Characterizations dialog box. Displays a list of ECal modules that are connected to the VNA.

Specify how the ECal module is connected dialog box help

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

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

Modify Mixer Cal dialog box help

Mixer Characterization ONLY. The Thru standard is not measured. Therefore, the Thru Cal Method choices are not available.

View / Detect ECal Characterizations  Available ONLY if using an ECal module. Invokes the Select ECal Module and Characterization dialog box.

Select the ECal Port to be connected to the Output of the Calibration Mixer dialog box help

Select the ECal Port to be connected to the output of the image filter of the Calibration Mixer / Filter combination. See connection diagram of Calibration Mixer / Filter combination.

Measure Calibration Standards dialog box help

Prompts for standards to be measured. Connect the standard, then click Measure.

Measure   Measures the mechanical standard and continue to the next calibration step.

[ReMeasure]  Replaces Measure after standard has been measured. Allows you to remeasure a standard.

Done  Click to proceed to the Calibration Complete dialog. Available only after all measurements for the calibration are complete.

Back  Returns to the previous dialog box.

Next   Does NOT make a measurement. Proceeds to the next required step.

Cancel  Exits the Calibration Wizard.

Vector Mixer Cal Steps dialog box help

Connect the Open, Short, and Load standards to the image filter output, then click Measure.'

This portion of the calibration characterizes the calibration mixer.

The connection is different depending on if the calibration mixer is an upconverter being characterized as a down converter.

Done  Click to proceed to the Calibration Complete dialog. Available only after all measurements for the calibration are complete.

Save Mixer Characterization dialog box help

Allows you to save the characterization data of your calibration mixer. When performing another VMC calibration using the same calibration mixer, this S2P file can then be recalled.

Browse   Navigate to the location where you want to save the characterization data of your calibration mixer. Either use the default file name or enter a custom file name.

Next  Saves the mixer characterization file and continues with the next step in the full system calibration routine.

Finish  Replaces Next if you are only characterizing the calibration mixer instead of performing a full system calibration. Saves the mixer characterization file and exits the mixer characterization routine.

Calibration Completed dialog box help

Finish  Save to the channel's calibration register.

Save As User Cal Set  Starts the Save as User Cal Set dialog box AND save to the channel's calibration register.

Cancel  Calibration is NOT applied or saved.

Learn about Calibration Registers.

Learn about User Cal Sets

Specify delay dialog box help

This dialog appears ONLY when Adapter Removal or Unknown Thru calibrations are performed.

The following values were estimated from the measurement. Most of the time, they are adequate. However, for CW sweep or frequency sweep with large step sizes, the accuracy of the values may be improved.

Adapter delay  To improve this value, measure and record the delay of the adapter with a dense step size. Enter that value here. The required precision value is the accuracy that is required to characterize the delay value.

Nominal phase offset  (Waveguide ONLY). To improve this value, measure and record the phase offset of the Waveguide adapter with dense step size. Enter that value here.

When one connector is coax and the other connector is waveguide, the phase offset has an ambiguity of 180 degrees. For consistency, the estimate provided here is always between 0 and 180 degrees. You can change this estimate to any value between -180 degrees and +180 degrees.

For FCA calibrations, this dialog box appears twice: once for the input frequencies and once for the output frequencies. The values can be slightly different.