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Frequency Converter Application

FCA includes both Scalar (SMC) and Vector (VMC) measurements and calibrations.

In this topic:

See Also

Examples

Other Application topics

FCA Options Explained

Comparison of SMC and VMC

 

Scalar Mixer Calibration

See Hardware setup

Vector Mixer Calibration

See Hardware setup

Overview

Provides highest Scalar accuracy for measurements of conversion loss/gain.

Optionally measures phase

Combines SOLT and power-meter calibration.

Simpler setup than Vector Mixer Calibration.

Provides unparalleled accuracy for measurements of relative phase and absolute group delay.

Uses combination of SOLT standards and a reciprocal mixer/filter pair during calibration.

More complicated setup and calibration procedure than Scalar Mixer Calibration.

After calibration, both reciprocal and non-reciprocal mixers and converters can easily be measured.

Measurements Offered

Both forward and reverse directions.

DUT can be connected to any VNA ports.

Amplitude response VC21

Phase response

Group delay

DUT input must be connected to VNA port 1.

DUT output can be connected to any other VNA port.

Equipment Required

Power meter and sensor

Reference mixer

Calibration mixer/filter combination (must be reciprocal  S21 = S12.)

Common equipment for both SMC and VMC

  • Mechanical cal kit or ECal module

See Comparison of Mixer Characterization using New Vector Characterization Techniques.

Requirements and Limitations

The following VNA features are NOT available with FCA:

How to make SMC or VMC Measurements

The following is an overview of how to make an FCA measurement:

  1. DECIDE to use either a SMC or VMC measurement. See a comparison of these two measurement types.

  2. CREATE an SMC or VMC Measurement.

  3. SETUP the measurements.

  4. CALIBRATE your SMC or VMC measurement.

Create an SMC or VMC Measurement

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

  2. Select SMC or VMC, then either:

  1. The default SMC or VMC measurement is displayed.

  2. See SMC measurements or VMC measurements to learn about the parameters that are offered in each.

How to make SMC or VMC settings

Using Hardkey/SoftTab/Softkey

Using a mouse

  1. Press Freq > Main > SMC Setup... or VMC Setup....

  1. Click Stimulus

  2. Select Frequency

  3. Select SMC or VMC Frequency...

Valid Mixer Configuration / Sweep Type Combinations

Configuring the SMC and VMC Setup dialog can be challenging at first.  RED messages like this one appear at the bottom of the Setup dialog to notify you of an invalid setup.

At least one range (Input, LO, or Output) MUST be Fixed.

The following are the Valid Mixer Configurations:

Sweep Type

Input

LO

Output

Linear

Swept

Swept

Fixed

Swept

Fixed

Swept

Fixed

Swept

Swept

CW Time

Power

Fixed

Fixed

Fixed

 

Tips

Although you will soon become comfortable navigating these tabs, at first it may be best to complete the dialog in the following order:

  1. For 2-stage mixers, select Mixer Setup settings.

  2. Select Sweep tab settings.

  3. Select Mixer Frequency settings.

  4. Select Power settings.

  5. Select Mixer (LO) Power settings.

 

The following FCA settings are common to VMC and SMC:

Sweep Tab - SMC and VMC dialog box help

Sweep Type

Linear  Sweep frequency. Measurements are displayed on a standard grid with ten equal horizontal divisions.  Learn how to select the range to display on the X-Axis.

CW Time  All ranges are set to a Fixed (CW) frequency, and the data is displayed versus time.

Segment Sweep  Sweep user-defined segments. Learn more.

Power  Sweep Input or LO power.

 

X-axis Point Spacing (Available only with Segment Sweep) - Learn about this feature

Avoid Spurs - Learn about this feature.

Reversed Port 2 Coupler (SMC ONLY)  Check when making SMC measurements with the Port 2 coupler reversed. Learn how. Do this to increase power at low frequencies. Checking this box has the following effects:

  • The measurement is faster because Reduce IFBW is no longer performed on SC21 measurements.

  • The SMC Calibration no longer attempts to level the Port 2 power (it is not possible to level the power through the coupler at those low frequencies). This keeps the VNA from producing “source unleveled” errors on Port 2.

Number of Points  Learn about this feature.

IF Bandwidth  Learn about this feature.

Phase Reference Point (SMC ONLY) Learn about this feature.

 

Learn about these buttons.

 

Power Tab - SMC and VMC dialog box help

Note: Set LO Power on the Mixer (LO) Power tab.

Configures Input and Output power settings for an FCA measurement. Use the Mixer Power tab to set LO power.

Power ON (All channels)  Check to turn RF Power ON or clear to turn power OFF for all channels.

Port Powers Coupled   Check to set the same power level at the DUT Input and Output ports. The LO power is NOT coupled. Clear to set power levels independently for each test port. Uncouple power, for example, to apply more power in the reverse direction than in the forward direction  Learn more about Setting Independent Port Power

DUT Input / Output Port

Select the VNA port that is connected to the DUT Input and Output. For VMC, the DUT input must always be connected to VNA port 1 because of the need for a reference mixer on port 1.

Power Level  Set the power level to the DUT Input port. To set power at the Output port, clear the Port Powers Coupled checkbox.

Source Attenuator Auto  Check to automatically select the correct attenuation to achieve the specified input power. Clear, then select attenuator setting that is used achieve the specified Power Level. Learn more about Source Attenuation.

All VNA channels in continuous sweep must have the same attenuation value. Learn more.

Receiver Attenuator  Specifies the receiver attenuator setting for the DUT port.

Source Leveling   Choose from: Internal (normal operation), Open Loop (used only for Wideband Pulse measurements), or Receiver - R1 for Receiver Leveling.

DUT Input and Output Port Power Sweep

Available when Power (sweep) is selected on the Sweep tab.

Input Start and Stop Power  To set Start and Stop power at the Output port, clear the Port Powers Coupled checkbox.

Note: If your DUT requires more input power than this setting allows below 3.2 GHz, use the PNA-X Hi-power mode, available from the RF Path Configuration dialog. The disadvantage to this is higher harmonic content.

Power Points  Number of power points to measure.

Power Step (Size)  Calculated value from current Start, Stop, and Points settings. This setting can NOT be changed directly.

Path Configuration  click to launch the RF Path Configuration dialog.

 

Learn about these buttons.

The following tabs are shared with all Mixer / Converter Applications:

Mixer Frequency tab - SMC and VMC Setup -dialog box help

Learn about this dialog

 

Mixer Setup tab - SMC and VMC Setup -dialog box help

Learn about this dialog

 

Mixer (LO) Power tab - SMC and VMC Setup -dialog box help

Learn about this dialog

FCA Segment Sweep

The following settings appear on the Mixer Frequency tab when Segment Sweep is selected on the Sweep tab.

Mixer Frequency tab - Segment Sweep - SMC and VMC dialog box help

How to configure a segment using the GUI:

  1. Click Add. Click Delete to remove a segment and renumber all subsequent segments.

  2. State is ON by default. Click OFF and that segment will not be included in the sweep.

  3. Configure Frequency settings for Input, LO, and Output ranges.

  • For each segment, the same sweep requirements apply as a standard (non-segment) sweep. For example, at least one range MUST be Fixed (Start = Stop frequencies).

  • The Input, Output, and LO frequencies of segments ARE allowed to overlap other segments.

  • All segments must sweep in either the forward (Start<Stop) or reverse (Start>Stop) directions. Mixed sweep directions are NOT allowed.

  • The following settings can be set independently for each segment:

How to add multiple segments using the GUI and Excel *.csv file:

Start with the GUI to set up mixer settings and to create the first segment then save it as a *.csv file. The *.csv file will then be opened in Excel and the additional segments will be entered. Learn more.

  1. Click Add.

  2. State is ON by default. Click OFF and that segment will not be included in the sweep.

  3. Configure Frequency settings for Input, LO, and Output ranges.

  4. Click on the Save... button.

  5. Select CSV (Comma delimited) (*.csv) to save the settings and first segment to a *.csv file.

  6. Open the *.csv file in Excel.

  7. Highlight the segment row then copy it.

  8. Paste the copied segment row to add the desired number of segments into the Excel file.

  9. Modify the settings for each added segment as necessary. The following is an example showing 3 segments:

  10. Save the *.csv file.

  11. In the GUI, load this *.csv file.

Learn about these buttons

Apply and Interpolate FCA Cal Sets

In general, when a Cal Set covers a wider frequency range than the channel, the VNA will offer to interpolate the Cal Set when it is applied. Learn more. However, with FCA measurements the LO frequency range may also be considered.

These same general concepts apply to segment sweeps. However, if ALL applicable frequency ranges (SMC: Input and Output and VMC: Input, Output, and LO) are NOT within those ranges of the measurement for ONE segment, then the Cal Set is NOT applied for ANY segment.

Select X-axis Display for FCA Measurements

Click Sweep > Main > X-Axis Type, then select the desired type.

When Sweep Type = Linear, you can choose to show the frequency range of any of the swept parameters on the X-axis.

For example, the following image shows an SMC Fixed Output response with the Input frequency range on the X-axis:

Output: 100 MHz (data trace)

Input: 2 GHz to 23 GHz (X-axis)

LO: 1.9 GHz to 22.9 GHz (not shown)

Marker annotation shows Output power at Input frequency.  

Save Trace Data

You can save your FCA measurement data in several standard formats.

Click Save Recall > Save Other > Save Data....

The following shows how CSV and SNP files are saved.

Mixer Trace Data

When you select Mixer Trace Data, the FCA data is saved to a CSV file in the following format:

#MIXER TRACE FILE,A.01.00

SegIndex, InputFreq, OutputFreq, LO1Freq, InputPower, LO1Power, SC21 Mag (dB), SC21 Phase (Deg)

SNP Format

Each record contains 1 stimulus value and 4 parameters (total of 9 values) as follows:

Stim  Real(p1)   Imag(p1)   Real(p2)   Imag(p2)   Real(p3)   Imag(p3)   Real(p4)   Imag(p4)

where pX is the parameter depending on measurement type:

Measurement Type

p1

p2

p3

p4

Scalar

S11

SC21 (FWD)

SC12 (REV)

S22

Vector

S11

VC21

VC12

S22

Mixer Characterization

Directivity

Source Match

Reflection Tracking

M21

All files contain the following Header Information: Brackets [  ] contain parameters.

!Keysight [Instrument Model Number]: [version]
!Mixer S2P File: [Mixer Measurement Type]
!Parameters: [Parameter List]
!Calibration State: [On/Off]

!# Begin Mixer Setup
![Mixer Setup parameters listed here]
![Mixer Parameter 1]
.
.
![Mixer Parameter n]
!# End Mixer Setup

# [S2P data here]

Avoid Spurs

On the Mixer Setup dialog box, check Avoid Spurs

The Avoid Spurs feature of the Frequency Converter Application attempts to prevent unwanted mixing products from appearing on the VNA screen. The Avoid Spurs feature does not significantly impact measurement speed.

Note: The Avoid Spurs feature is OFF by default for FCA calibrations.  For highest accuracy, make measurements with the Avoid Spurs feature at the same state (ON or OFF) as was used when calibrating.

Description

A spur, or spurious signal, is a term used to describe the unwanted product of two signals mixing together. When you configure the mixer setup dialog box for a desired Output, the VNA computes the frequencies of potential unwanted signals.  By manipulating internal VNA hardware, these signals are avoided and do not appear on the VNA display. This means you do not need to use external filters to prevent spurious signals from appearing on the VNA display.

The time required for the VNA to compute the frequencies of unwanted spurious signals MAY be noticeable depending on the number of data points in your measurement. However, once computed, the time required for the VNA to avoid the spurs is usually insignificant.

Limitations

The Avoid Spurs utility cannot avoid every spur. However, when there is a choice of spurs to avoid, it will avoid the largest spur.

The Computation of Avoided Spurs

The Avoid Spur computer avoids the following spurs: