PNA Frequency Converter Application Known Issues

The following are known issues with the Frequency Converter Application (Option 083) as of the date below. As these issues are resolved, you can update your PNA firmware at no cost by using the AgileUpdate utility (menu: System, Service, AgileUpdate). Firmware is constantly being developed and new releases are planned on regular intervals.

Please refer to "What's New in PNA Code Version x.x" located in the PNA Help system for new FCA features introduced in each firmware revision.

Note: Please submit FCA issues that you find, as well as enhancement requests, to fca_support@agilent.com

The following FCA known issues currently exist in PNA Firmware Revision A.06.01.05:

1. Measurements of Converters with Embedded LOs

   Amplitude-only transmission measurements can be done on converters with internal LOs if the LO frequencies are precisely known and stable. Phase measurements (including group delay) on converters with embedded LOs can be done with high accuracy if there is access to the internal LO signal(s). For double and triple-stage converters, it will be necessary to combine, filter and amplify the LOs to create a single alternate-LO for use during calibration and measurement. If access to the LO signal(s) is not available but an external time base can be supplied to phase-lock the oscillators, then phase measurements may still be done using an external signal source for the reference mixer. The external signal source must be locked to the same time base as the embedded LOs. In this case, the phase/group delay measurements will be considerably noisier compared to measurements done when all the LOs in the test system are phase synchronous, and aggressive smoothing and averaging will probably be required for acceptable accuracy. An application note describing these measurements is currently being developed.

2. Loss of external source control after hibernation

   If the PNA is hibernated in the middle of a FCA measurement in which an external source is under FCA control, and then the PNA is restarted, a VISA error message will appear stating "VI_ERROR_INV_OBJECT."

   To correct this problem, the 82357A USB/GPIB interface must be reinitialized after hibernation. This is done by clicking on the accept button in the interface initialization dialog window. The green "Ready" light on the interface will turn on.

3. Problem performing a mixer setup using SCPI or COM

   If performing a mixer setup using SCPI or COM, you should first set the number of stages before setting other mixer setup parameters. Unexpected results may occur if you set the number of stages AFTER making other settings. The default setting for number of stages is 1. Therefore, if testing a 1-stage mixer, you do not have to make this setting.

4. R1 and B measurements cannot be corrected with a VMC calibration

   In rev. A.04.83, R1 and B have been added as new measurements that can be created in a VMC channel. However, these measurements cannot be corrected with a VMC calibration. Therefore, if one of these measurements is active at the time a VMC cal wizard is started, the calibration will proceed normally, but cal will not turn on at the end and an error message will be displayed. Also if you attempt to turn on a VMC cal when R1 or B is the active measurement, you will get a similar error message. The VMC calibration will indicate that it is on when in fact it is not on.

5. VMC data may be lost after switching to R1 and B measurements

   You may loose the VMC measurement data if you switch to R1 and B measurements with the VMC cal turned on and in single sweep mode.

   To recover the data, you must by take another sweep after returning to the previous VMC measurement.

6. Using Instrument State files *.cst, *.sta containing FCA setups

   Instrument state files *.cst, *.sta containing FCA setups created in PNA firmware revisions prior to A.06.01.05 cannot be recalled with revision A.06.01.05.

   Suggestion: First save the mixer configuration file *.mxr using the previous firmware revision, then load it into firmware revision A.06.01.05.

   Note: A controlled LO source must be setup in A.06.01.05 using the same name as the previous firmware revision.

7. Displayed data for LO on high side of RF & IF is reversed from firmware rev. A.04.87.01

   The data for a calibration where the LO signal is on the high side of the RF & IF signals will be displayed reversed on the x-axis from the way it was displayed in firmware revision A.04.87. The x-axis will display descending frequencies to match the descending frequency data. Remote programs that download the data only without the matching x-axis frequency list will need to be revised for firmware revision A.06.01 or higher.

8. Deleting and reconfiguring an external source

   Deleting a previously configured external source and then adding it again using the same name will cause the source to not be configured.

   To correct this problem, delete the source and then exit the External Source Configuration dialog box before reconfiguring, or delete the source and then give the source a different name when reconfiguring.

9. Generic source control does not function

   The generic source commands do not configure correctly when a generic source is setup using the External Source Configuration dialog box. The firmware is adding the parameter "CW" to command "Set CW Sweep Mode".

   To correct this problem, open the Generic Source Commands dialog box and edit the "Set CW Sweep Mode" command. Remove the parameter "CW" so the command will read "FREQ:MODE".

10. Avoid Spurs selection not available

    The Avoid Spurs selection under the Trace, Measure menu is not available. Avoid Spurs can be selected from the Mixer Configuration dialog box.

FCA History (Issues fixed)

1. Frequency Offset as part of User Preset Not Supported

   Although the PNA will allow it, do NOT save a Frequency Offset or Frequency Converter Application measurement as part of a User Preset. FCA calibrations started after saving and recalling this type of user preset are likely to produce erroneous results.

   Suggestion: Save the Frequency Offset or Frequency Converter Application measurement as a .cst file and recall it as required.

2. Save FCA .S2P files from the Trace Menu

   The only way to save Frequency Converter .S2P files is to click Trace, Scalar or Vector Mixer/Converter, then Save Data to File. Do not click File, Save As... to save FCA .S2P data files.

3. Changing Stimulus Settings outside of the Mixer Setup Dialog Box (Copy Channels)

   Although the PNA display will respond, changes to the stimulus settings of an FCA measurement can ONLY be made using the Mixer Setup dialog box. Currently, the following PNA feature allows, but does not actually change, FCA stimulus settings:

   Copy Channels - Copying channel settings to a channel with an FCA measurement will cause the display to change but the actual stimulus settings, as viewed in the Mixer setup dialog box, do not change.

   NOTE: In rev. A.06.01.05, the copy channels menu selection is disabled when using FCA.

4. Remote setup of a mixer object

   When using the remote interface (COM or SCPI) to set mixer parameters individually, you must setup the mixer first and then validate the setup using the Calculate command or Apply command before calibration.
   
   There are two ways to setup a mixer object remotely:
   1. Load a text file with mixer parameters
   2. Set mixer parameters individually.
   
   The save command saves parameters for mixer setup to a text file. This text file can then be edited. Next, the text file is loaded using the load command. The load command validates and applies the mixer parameters to the PNA channel after loading the text file.
   
   Setting the mixer parameters individually does not apply the parameters until the Calculate command is used (Mixer.Calculate or SENSE:MIXER:CALC) or the Apply command is used (Mixer.Apply or SENS:MIX:APPLy). If this is not done when using the remote interface, then the query command will time out (the PNA will not respond to the query.)
   

   NOTE: In rev. A.06.01.05, the procedure for remote setup of a mixer object is documented in the PNA Help system.

1. Channel Conflict

   FCA measurements and non-FCA measurements can NOT share the same channel. Also, two different TYPES of FCA measurements can not share the same channel, (for example, a Vector Mixer/Converter measurement and a Scalar Mixer/Converter Forward measurement).

   The FCA application will not allow these conditions. An error message will appear on the screen indicating that the two measurements are incompatible.

   NOTE: In rev. A.04.83, the error message no longer appears. Instead, when there is a conflict, the FCA measurement will be automatically setup in the next available channel.

2. Only Linear Sweep (Step Sweep) Supported with FCA Measurements

   Although you can change sweep type by using the PNA Menu bar, the only sweep type currently supported with FCA measurements is Linear step sweep.

   NOTE: In rev. A.04.83, in addition to linear sweeps, power and CW sweeps are supported in FCA. The only thing to remember is that the CW frequency for the power sweep or the CW sweep has to be within the input frequency range of the current mixer setup configuration (for calibration to stay on).

3. Problem with external LO source control name

   The external LO source controlled by FCA needs to have the same name. When a mixer setup with external LO source control is saved to an instrument state file, the LO source name is saved. If the same name is not setup in the external LO source control dialog list when the setup is recalled (i.e. the source is re-named or deleted from the list), then the PNA application will crash.

   NOTE: In rev. A.04.83, if the recalled source is not found in the current source configuration (external source control dialog list), the mixer setup for the missing LO source will change to "Not Controlled".

4. Corrected fixed output (fixed IF) VC21 measurements not supported

   NOTE: In rev. A.04.83, you can perform a corrected fixed output (fixed IF) VC21 measurement. Please refer to "What's New in PNA Code Version 4.8" located in the PNA Help system for details of this new FCA feature.

1. Fixed IF VC21 Measurements Not Supported

   Vector transmission measurements can NOT be performed.

   NOTE: In rev. A.04.25, you can perform an uncorrected fixed IF VC21 measurement. However, the measurement cannot be calibrated.

2. PNA crashes when using an external source under FCA control

   When making an FCA measurement using an external source under FCA control, the PNA may crash. This could be caused by the following:

   • Agilent I/O Library no longer running. To check, look in the Windows task bar of the PNA for the I0 icon. If not present, restart the IO library. Click Start, Programs, Agilent I/O Libraries, IO Control.

   NOTE: In rev. A.04.25, this condition now causes an "External Source Not Found" error message to be displayed.

3. Front Panel Measure and Marker Function buttons invoke the wrong dialog boxes

   With an FCA measurement active, if you press the Menu/Dialog button on the front panel, and then either the Measure or Marker Function buttons, then the standard PNA dialog boxes are displayed instead of the FCA dialog boxes.

1. Fixed IF Measurements Not Supported

   To produce a fixed IF measurement, the Input and LO frequencies need to be swept together at exactly the same time. Although the external LO source is controlled by FCA for fixed LO measurements, the FCA does not synchronize the PNA source sweep with an external LO source sweep.

   Suggestion: You can accomplish this measurement through an external program. Step the PNA Input source in CW, then step the external LO source, then make a measurement. FCA measurements are supported through COM or SCPI commands.

   NOTE: In rev. A.04.06, you can perform fully corrected Scalar (SC21) fixed IF measurements.

2. Changing Stimulus Settings outside of the Mixer Setup Dialog Box (Marker functions)

   Although the PNA display will respond, changes to the stimulus settings of an FCA measurement can ONLY be made using the Mixer Setup dialog box. Currently, the following PNA feature allows, but does not actually change, FCA stimulus settings:

   Marker functions - Changes the Stop, Start, Center and Span frequencies to the current Marker location. For example, in an FCA measurement, Marker ==> Center Frequency will attempt to change the PNA center frequency to the X-axis location of the marker. The display will change but the actual stimulus settings, as viewed in the Mixer setup dialog box, will not change.

3. Ripple in conversion loss measurements

   When measuring the conversion loss of a mixer where the mixer output response is going from high frequency to low frequency (reverse direction), you will see additional ripple on the measurement. An example of this is when the LO frequency is greater than the input OR output frequencies and the Input - LO calculation is chosen. The amount of additional ripple seen is related to the amount of mismatch between the mixer output and the PNA. This problem should be fixed in the next release of software.

   Suggestion: Use an attenuator to improve the match between the mixer output and the PNA to minimize the amount of additional ripple.

1. Recalling FCA secondary measurements

   Primary FCA measurements (SC21, SC12, VC21) can be changed to secondary measurements (S11, S22, Incident Power, or Output Power). However, when a secondary measurement is saved as part of an instrument state (.sta or .cst file) and then later recalled, the default primary FCA measurement will be displayed.

   After the state is recalled, the secondary measurement can be selected for display.

2. SMC incident power measurement data to memory results in corrupt data in memory

   If a SMC forward or reverse measurement with incident power is displayed and the data is saved to memory, corrupt data will be stored in the memory buffer.

3. Error calculating the input frequency in FCA mixer setup dialog

   When computing the input frequency from the output and LO frequencies in the FCA mixer setup dialog, the calculated input frequency will be incorrect.

   To avoid this problem, manually set the input frequency or set the input and LO frequencies and then calculate the output frequency.

4. Problems with creating a mixer characterization file

   The characterize mixer only selection in the FCA calibration selection menu does not work and will result in corrupt data in the mixer characterization file.

   To avoid this problem, perform a full FCA calibration with forward sweep and save. The mixer characterization file can then be used. This will only work for forward sweeps. If a reverse sweep is performed the data in the mixer characterization file will be reversed in frequency and will need to be reordered.

5. Corrections to documented mixer SCPI commands

   The following are corrections to the documentation for MIXer SCPI commands:
   
   

   Documented SCPI command -- Corrected SCPI command
   
   • MIXer:OUT:FREQuency:FIXed -- MIXer:OUTPut:FREQuency:FIXed
     
   • MIXer:OUT:FREQuency:SIDeband -- MIXer:OUTPut:FREQuency:SIDeband
     
   • MIXer:OUT:FREQuency:STARt -- MIXer:OUTPut:FREQuency:STARt
     
   • MIXer:OUT:FREQuency:STOP -- MIXer:OUTPut:FREQuency:STOP
     

6. Corrections to mixer SCPI commands implemented in A.03.23

   The following are corrections to the MIXer SCPI commands for A.03.23 only. They will be present in the next release for backwards compatibility only. All future programming should use the proper SCPI command.
   
   

   Proper SCPI command -- SCPI command implemented in A.03.23
   
   • MIXer:INPut:POWer -- MIXer:INPut:FREQ:POWer
     
   • MIXer:LO:POWer -- MIXer:LO:FREQ:POWer
     

1. Applying Cal Sets to an FCA Measurement

   When applying an existing Cal Set to an FCA measurement, the Mixer Setup must be identical to, or an acceptable subset of, the values contained in the applied Cal Set. To learn more about "acceptable" subsets, see Cal Sets. The PNA does NOT automatically make the corrections to the Mixer setup after applying a Cal Set that does not match. Although the PNA may indicate that it is changing the channel parameters to match the Cal Set, it does not change the necessary mixer-test parameters.

   If the setup does not match the applied Cal Set, your measurement data will be corrupt.

2. Cal Set MAY NOT apply to an FCA Measurement

   After an FCA calibration occurs, a Cal Set is saved and is immediately applied to the active measurement. In some very rare cases, you may perform a calibration for an FCA measurement and find that the correction will not turn ON. Actually, the Cal Set that was just saved can NOT be applied to the measurement due to a floating point rounding problem.

   Suggestion: Change either the Input, Output, or LO frequencies and re-calibrate.

3. Limit line usage with Scalar Mixer/Converter (forward or reverse) requires special steps.

   To use limit lines with Scalar Mixer/Converter measurements:

   • Place the measurement trigger setting to Hold.
     
   • Setup the limits in the limit table.
     
   • Return the triggering mode to its normal state.
     

4. SCPI commands NOT available for Frequency Converter Application

   Currently, COM is the only remote interface that is available to control the Frequency Converter Application. With COM, you can remotely perform a mixer setup. You can NOT perform a Scalar or Vector calibration. See the Mixer Object with related properties and methods.

5. Recalling an active FCA measurement

   A common method used to change FCA measurement parameters is through the Menu selection Trace, then Scalar or Vector Mixer / Converter. This Menu selection is only available when the active trace is an FCA measurement.

   When you recall a .cst or .sta file that includes an active FCA measurement, the previously stated Menu selection will NOT appear. You must first re-activate the trace by clicking the Trace Status button to the left of the trace.

6. Recalling FCA secondary measurements

   Primary FCA measurements (SC21, SC12, VC21) can be changed to secondary measurements (S11, S22, Incident Power, or Output Power). However, when a secondary measurement is saved as part of an instrument state (.sta or .cst file) and then later recalled, these secondary FCA measurements will appear as if they are not triggering.

   To avoid this problem, save the instrument state with only SC21, SC12, or VC21 measurements. After recalling the state, then change to a secondary measurement (S11, S22, Incident Power, or Output Power).

7. Cannot change stimulus settings of a secondary measurement

   You cannot change the stimulus settings of a secondary measurements such as S11, S22, Incident Power, or Output Power.

   First change the measurement to its primary measurement (SC21, SC12, or VC21), then change the stimulus setting using the mixer setup dialog or other supported interfaces, then change back to the secondary measurement.

8. Cannot apply source power calibration to a SMC reverse measurement

   A source power calibration does not work when applied to a reverse SMC measurement.

9. Avoid Spurs function does not work during SMC and VMC calibrations

   The avoid spurs function does not work during the SMC and VMC calibrations. After the calibration is finished and applied to the measurement, there may be spurious responses (spurs) in the measurement.

   To avoid this problem, uncheck the "Avoid Spurs" check box before calibration and during measurement. The check box is located in the mixer setup screen.
   
   Recommendation: An IF bandwidth of 1000 Hz or less is recommended for calibration and measurement to minimize spurs.
   
   Suggestions: One method to avoid spurs during calibration and measurement is to change the start or stop frequency slightly. Another method is to use filters to reject unwanted frequency components in the IF output of the reference mixer and/or mixer under test.

10. Source match correction on SC12 measurements

    Source match correction is not being properly applied to SC12 measurements, which results in more ripple in the corrected measurement.

11. Presence of option 081 reference switch not checked

    Customers who have purchased the E8361A 67 GHz PNA with option 083, should not attempt to set up vector mixer measurements or run the VMC calibration. The instrument lacks the required hardware option 081, but the software is not checking for this option and attempting vector mixer measurements or VMC calibration may cause the application to crash. Scalar mixer measurements and SMC calibration are fully functional on the E8361A with option 083.

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