Use the RTG Calibration Utility to calibrate the RTG.

To give users the ease of creating or modifying calibration files, RTG now comes packaged with a Calibration Utility. The Calibration Utility provides access to the required calibration parameters to be used within RTG. The Calibration Utility can be run through the main RTG application user interface or independently as a separate application.

Currently the Calibration Utility only supports local RTG systems.

The following figure depicts the RTG Calibration Utility state machine.

Figure 39. RTG Calibration Utility State Machine

The states are as follows:

  • Idle—RTG Calibration Utility is configurable.
  • Calibrating—RTG Calibration Utility is executing loopback calibration.
    • The RTG Calibration Utility only supports calibrating a single VST instrument at a time.
    Note RTG system calibration is not currently supported though gRPC.

    An RTG operates accurately when it is calibrated in the region of its operation. An RTG runs with a fixed Center Frequency and Reference Level; these two parameters define a unique calibration data set. A calibration file can contain as many calibration data sets as are needed to cover the expected range of operation.

    Note When using a coprocessor, data path and coprocessor minimum latency are two additional keys that define a unique calibration data set.
    Note The RTG software does not have a way to inform the user of valid existing calibration data. The user must either already know that valid calibration data exists on disk and will be used or must connect the system into loopback to be safe.
    Note Do not initialize the instruments in the RTG User Interface before performing calibration. All calibration parameter configuration occurs in the RTG Calibration Utility window.
    Note NI recommends performing a self-calibration of the VST if self-calibration was not performed recently. Refer to the VST documentation for information about performing self-calibration on the instrument.

    The process to create a calibration data set is as follows:

    1. Create a loopback connection between the output and input of the test fixture as shown in the following figures.
      Figure 40. Test Fixture Loopback Connection


      Figure 41. Attenuation Sources


    2. Launch the RTG Calibration Utility in one of the following ways:
      • Run RTG Calibration Utility.exe from the <Program Files>\National Instruments\RTG\calibration-utility folder on the host computer.
      • From Windows, select Start » RTG Calibration Utility.
      • From the RTG UI, select Calibration from the Utility menu.

      The RTG Calibration Utility opens.

      Figure 42. RTG Calibration Utility


      Instrument Name Field
      Center Frequency Field
      Reference Level Field
      External LO Disabled/Enabled Button
      LO In Frequency Field
      LO In Power Field
      Calibration Utility Status Indicator
      Recommended LO In Frequency Indicator
      Recommended LO In Power Indicator
      Start Calibration Button
      Abort Calibration Button
      Minimum Latency Indicator
      Minimum Common Attenuation Indicator
      Maximum Common Attenuation Indicator
      Calibration Result Indicator
      Calibration Status Indicator
    3. Select the VST to be calibrated from the Instrument Name field.
    4. Enter the Center Frequency to be calibrated.
    5. Enter the value for the Reference Level to be calibrated.
      Refer to Reference Level and Pulse Detection Calibration for more information about configuring this field.
    6. If you are connected to an external Local Oscillator (LO), configure the following:
      1. Click the External LO Disabled button to enable.
      2. Enter the LO In Frequency value (to the RTG center frequency or to a different frequency within the upconverter/downconverter passband) in the LO In Frequency field.
        Note NI recommends setting the LO In Frequency to the RTG center frequency during calibration.
        The RTG software returns the expected LO In Frequency value based upon the VST instrument and center frequency in the Recommended LO In Frequency indicator.
      3. Enter the LO In Power value.
        The RTG software returns an expected LO In power based upon the mid-point value of the input range for a specific VST model in the Recommended LO In Power indicator.
    7. Click Start Calibration to begin the calibration process.
      Note The process takes several minutes to complete.
      Note You can click Abort Calibration to return to the Inactive state before calibration completes. During some phases of system self-calibration, clicking Abort Calibration may not result in immediately moving RTG to the Idle state. The RTG Calibration Utility receives the Abort Calibration call, but waits until the current stage of the calibration to complete before moving to Idle.

      While calibration is executing, the following occurs:

      • Software updates the calibration status and calibration utility status on the RTG Calibration Utility UI.
      When calibration completes, the following occur:
      • A calibration data set is written to the calibration file.
      • The Calibration Utility UI displays the calibration results for the Minimum Latency, Minimum Common Attenuation, Maximum Common Attenuation, and Calibration Result.
      • The Calibration Utility UI returns to the Idle state.
    8. Repeat steps 1 through 7 for all VSTs to be calibrated.
    9. After calibration is complete, do one of the following:
      • Calibrate with a new set of parameters.
      • Exit the RTG Calibration Utility.
    Refer to Initializing Instruments and Opening a New Session in the RTG Software to use the calibration data.

    Saving and Using Stored Calibration Data

    Running the RTG Calibration Utility saves data so that future RTG sessions with the same Center Frequency and Reference Level settings (as well as Data Path and Coprocessor Minimum Latency if using a coprocessor) can operate accurately.

    RTG self-calibration features the following default behavior:

    • Running the RTG Calibration Utility that returns a PASSED Calibration Result saves the calibration data to disk.
      Note Run the Data Clearing Utility to remove any previously saved calibration data. Refer to Using the Data Clearing Utility for more information.