Scalar Mixer/Converter Measurements (SMC)

The following information is unique to SMC:

See Also

Programming Commands

SMC Hardware Setup

SMC requires a power meter/sensor, two sources, and a Cal Kit or ECal module

Create an SMC Measurement

  1. Press Setup  > Main > Meas Class....

  2. Select SMC, then either:

  1. An SC21 measurement is displayed.

SMC Parameters Offered

To select additional parameters to display, click Trace, then click on a new trace, then select a parameter from the list.

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.


The DUT input and output can be connected to any VNA ports.

Note: Although there are MANY configuration possibilities, the following images and descriptions show ONLY a DUT connected to VNA ports 1 and 2.


   Black are ratioed measurements (test port/reference receiver).

   Green are unratioed measurements (either a test port OR reference receiver).

DUT Input to VNA port 1

DUT Output to VNA port 2

DUT Input to VNA port 2

DUT Output to VNA port 1


  • SC21  (Conversion Loss)  Stimulus at Input, response at Output (B/R1).

  • SC12 (Reverse Isolation)  Stimulus at Output, response at Input (A/R2)

  • S11  (Input match)  Stimulus and response at Input (A/R1)

  • S22  (Output match)  Stimulus and response at Output (B/R2)


  • SC12  (Conversion Loss) Stimulus at Input, response at Output (A/R2)

  • SC21 (Reverse Isolation)  Stimulus at Output, response at Input (B/R1)

  • S11  (Output match)  Stimulus and response at Output (A/R1)

  • S22  (Input match)  Stimulus and response at Input (B/R2)

Unratioed  Absolute test port receiver measurements. The receiver is automatically selected depending on the DUT configuration.

    • IPwr  (Incident Power) - stimulus and response at Input.

    • RevIPwr  (Reverse Incident Power) - stimulus and response at Output.

    • OPwr  (Output Power) - stimulus at Input, response at Output.

    • RevOPwr  (Reverse Output Power) - stimulus at Output, response at Input.

SMC Mixer Setup

How to start the SMC Mixer Setup dialog

Using Hardkey/SoftTab/Softkey

Using a mouse

  1. Press Sweep > Main > SMC Setup... > Mixer Setup tab.

  1. Click Stimulus

  2. Select Sweep

  3. Select SMC Setup...

  4. Select Mixer Setup

The following SMC Mixer Setup dialog tabs are presented:

Speed Up SMC Measurements

Using default SMC settings, any calibrated SMC measurement requires four sweeps. However, you can reduce the number of sweeps required by selecting one or more of the following settings.

Use Nominal Incident Power

Click Response, then Measure, then Use Nominal Incident Power  

Each data sweep of a fully corrected SMC transmission measurement actually requires FOUR data sweeps. When you clear Use Nominal Incident Power, the reference receiver (R1 or R2) does NOT measure incident power. Instead, the incident power is assumed to be at the level that was set with the Source Power Calibration that is done as part of every SMC measurement. The degradation in accuracy is very negligible if the input or output of your DUT is well-matched.

This selection eliminates sweeps ONLY when both Include Input Match AND Include Output Match is cleared on the Cal Type dialog. Learn more.

Apply a Cal Set or SMC Cal Type

You can create an FCA measurement and apply an existing Cal Set as you can with any VNA measurement. Learn about Cal Sets. In addition, from a Cal Set, you can apply a specific SMC Cal Type to an existing SMC measurement.

How to apply an SMC Cal Type

  1. Create an SMC measurement

  2. Calibrate or apply an existing SMC Cal Set, then...

Using Hardkey/SoftTab/Softkey

  1. Press Cal > Main > Correction Methods....


Correction Method dialog box help

By default, each SMC calibration requires FOUR sweeps. Clearing boxes will eliminate sweeps and speed up your SMC measurements. The difference in speed is most noticeable when making fixed input or fixed output measurements with an external LO source.

Include input match correction  Check to perform a sweep to measure and correct for INPUT match. Clear this box if the input of your mixer is well-matched to the VNA, or if your setup does not permit a valid S11 measurement.

Include output match correction  Check to perform a sweep to measure and correct for OUTPUT match. Clear this box if the output of your mixer is well-matched to the VNA, or if your setup does not permit a valid S22 measurement.

Include SC12 Sweep  Check to perform a reverse sweep to measure SC12.

  • When checked (default setting), a calibrated SMC measurement sweeps in both forward (SC21) and reverse (SC12) directions.

  • Clear this checkbox to eliminate sweeps in the reverse direction. This means that the following measurements will NOT be corrected: SC12, RevOPwr, RevIPwr.

Corrected Parameters  Lists the parameters that can be corrected given the boxes that are currently checked. These parameters may not be currently measured.

Calibration Type  Shows the type of SMC Cal that will be applied given the boxes that are currently checked.

Learn about Use Nominal Incident Power

How many sweeps can be eliminated?


Parameters Learn about parameter abbreviations

# of sweeps

ALL checked and clear Use Nominal Incident Power


4 Total

Perform this action...

 to REMOVE these parameters...

and these sweeps

Clear "Include SC12"

Remove RevIPwr,RevOPwr,SC12

Removes 1

Clear "Include OUTPUT match

Remove S22

Removes 1 when Nominal is checked*.

Clear "Include INPUT match"

Remove S11

Removes 1 when Nominal is checked*.

Check "Use Nominal Incident Power"

Remove IPwr, RevIPwr

May remove up to 2*

ALL cleared and check Nominal Incident Power


1 Total

*S11 shares a sweep with IPwr and S22 shares a sweep with RevIPwr. Therefore, when Include Input Match or Include Output Match is checked, then checking Nominal incident power does nothing.

VMC measurement sweeps can NOT be eliminated.

SMC Calibration Overview

Note: [M937xA/P937xA] Before SMC Calibration, perform the System Receiver Cal. The Cal All Wizard guides you through the calibration process.

The SMC Calibration Wizard guides you through this process.

When applying a Phase Reference cal set, step 1 (power cal) is NOT performed.

  1. Connect a power meter / sensor to VNA Port 1. At each step of the input and output frequency, the VNA measures:

  2. Perform two Full 2-port calibrations: one over the INPUT frequencies and one over the OUTPUT frequencies of the DUT. (If your DUT is a linear device, the calibration uses only the INPUT frequency range.) Use either a mechanical calibration kit or an ECal module.

For Mixers / Converters with High-output Power

The Unknown Thru method is NOT valid when there is over 40 dB of combined loss in the Unknown Thru and calibration path. In this case, the following calibration and correction method is recommended.

SMC Cal Wizard

NOTE: The Smart Cal wizard is not available for the M937xA/P937xA

The following dialog boxes are presented during an SMC Calibration.

Indented steps are optional.

How to Perform a SMC Calibration

  1. Create an SMC 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...


SMC Calibration Setup dialog box help

Allows you to review and change the settings for your SMC calibration.

Note: With release A.09.90 and before, checking both 'Independent power cals' AND 'Use Phase Reference Calset' would generate an error after performing the calibration. With releases AFTER A.09.90, the two settings are compatible.

Waveguide/In-fixture/On-Wafer Setup  Click Next to launch the following Setup dialog box.

Independent power cals for input and output ports (no thru)  Check if a Thru standard is NOT available. During the power cal, you will be prompted to connect the power sensor to the Input, then the Output port.

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).

Phase Correction

Enable Phase Correction  Check to enable Phase measurements.

Choose one of the following methods to specify the delay through the characterized mixer. With the first two methods, the phase delay through a Calibration Mixer is measured and compared to the known delay, either entered, or stored in an *.S2PX file.

  • Use Known Mixer Delay  Enter the fixed, known, delay through the calibration mixer.

  • Use Characterized Mixer  Select, then browse to the *.S2P file that characterizes the calibration mixer.  Use an *.S2PX file when making segmented SMC + Phase measurements. Learn more. Use either of the following two methods to characterize the Cal Mixer over the SMC measurement frequency range:

    1. Use the Mixer Characterization Wizard. (Click Response, then Cal, then Mixer Characterization Wizard.) The Cal Mixer has the same requirements as the VMC Cal Mixer. Learn more.

    2. In a calibrated VMC channel, measure the group delay of the calibration mixer, then save to an *.S2P or *.S2PX file. However, a characterized mixer is required to calibrate the VMC channel.



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.


  • Interpolation is performed when more frequencies are included in the file than in the channel, and the data points do not exactly match those of the measurement.


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.

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, then click Next, to start the Modify Frequency Cal dialog.

Source Cal Settings  Click to start the Source Cal Settings dialog.


Modify Frequency Cal dialog box help

This dialog appears only when Modify Cal is checked on the previous dialog.

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.


Power Cal Settings dialog box help

Note: A Use Power Table checkbox (not shown) is available when a mmWave SMC measurement is active. Learn more.

Power Cal at: Select the source port for which a Power Calibration will be performed. The source and receiver correction will be transferred to all other sources and receivers involved in the S-parameter measurements.

Use Multiple Sensors  Check this box when you want to use more than ONE power sensor to cover the measurement frequency range. The dialog is replaced with the Multiple Sensors dialog. When "Use Multiple Sensors" is cleared (default setting), connect only ONE sensor to the VNA.

Note: Use Multiple Sensors is a Licensed Feature called Multiple-sensor Power Calibration for SMC/GCX. Learn more about Licensed Features.

Power Meter Settings  Click to start the standard Power Meter Settings dialog.

De-embed (power sensor) adapter  When the power sensor connector is NOT the same type and gender as the DUT connector for the specified port, then for optimum accuracy, extra cal steps are required to measure and correct for the adapter that is used to connect the power sensor to the reference plane.

Clear this box to NOT compensate for the added adapter.

Check this box to perform extra calibration steps to measure and correct for the adapter.

Then select the Power Sensor Connector type and gender of the power sensor. "Ignored" does NOT compensate for the added adapter, just as if the checkbox were cleared.

When this connector matches the DUT connector for the same port, then the VNA assumes that there is no adapter. Extra cal steps are NOT required and the Cal Kit selection is not available.

Otherwise, select the Cal Kit to be used to calibrate at the adapter.

See Accuracy Settings below.


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.


SMC Calibration Steps dialog box help

Power Level at which to perform the Power Cal.

It is usually best to set power level to 0 dBm at the power sensor because the power sensor is calibrated at that level. Lower power levels will yield a slower and noisier calibration.

If an external component is used between the PNA-X test port and the calibration reference plane, then adjust the power level so that the power at the sensor is about 0 dBm if possible.

The current source attenuation value is shown on the dialog.

LO Power Cal (Optional) When enabled, perform a Source Power Cal at the DUT LO connector. An LO must already be selected. Learn how. The power level of the LO source calibration is set on the (LO) Power Tab.


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