System Calibration Dialog

System Calibration is used to establish a system reference plane at the connector where the calibrator device is connected. It creates a calibration file that is applied as an RF Radio Frequency: A generic term for radio-based technologies, operating between the Low Frequency range (30k Hz) and the Extra High Frequency range (300 GHz). Calibration File, part of User Correction.

Physical Channel - The user connects the U9361x RCal Receiver Calibrator to the analyzer physical channel being calibrated and selects that physical channel on the System Calibration panel. The U9361 external reference (Ext Ref In 10 MHz Megahertz: A unit of frequency equal to one million hertz or cycles per second. connector on the U9361) must have the same frequency reference as the analyzer.

The System Calibrator hardware configuration is selected from the System Calibrator dropdown list.

Steps for Setup - Opens a help page with directions for setting up a system calibration.

System Calibrator - The System Calibrator drop-down list selects the System Calibrator hardware configuration.

Status Indicators - To the right of the System Calibrator selection is a status indicator that informs the user if RCal license support was installed. The VSA software installer has an optional RCal setup under the Hardware Support menu. The RCal utility installs a Windows service that checks the RCal comb calibration license.

- There is a problem with the RCal utility installation. You can hover the mouse over the icon to get a tooltip with more information.

- The RCal utility is installed and running.

Folder - The Folder control is used to specify where to store the calibration data file generated by System Calibration. By default, the calibration file generated by System Calibration is created in a folder named for the current hardware configuration. The user has the option to browse to a different location.

Filename - The default filename for the calibration file is Cal.cal. The user has the option to set a different, descriptive name. If a file with the specified filename already exists, a warning indicator is displayed to caution the user that the existing file will be overwritten when Calibrate is executed.

The filename is also used in naming a setup file that is optionally saved when Calibrate is executed. See Save Setup After Calibration, below. It is recommended that the filename be descriptive of the setup to assist in management of multiple calibration data files.

A key is added to the Windows registry by the VSA installer that enables the contents of .cal files to be displayed as text in the Windows File Explorer preview pane. The header of calibration data files created by System Calibration has information about the analyzer setup used for calibration. The ability to view this content in the Preview pane will assist the user browsing calibration data files for the desired file.

Calibration Disables Existing User Corrections - When this value is true, all User Correction RF Calibration files are disabled before any measurements are made when Calibrate is executed. When this value is false, the current state of User Correction RF Calibration files is unchanged when calibration measurements are made. This value is true by default.

Frequency Range Auto - When this value is true, system calibration frequency range is set automatically by tracking the current measurement frequency span. When this value is false, a custom frequency span can be set. This value is true by default.

If the analyzer has a mixer in the front end, it is recommended that when this property is turned off (false), the manually set calibration frequency range is within the measurement frequency span.

Start Frequency - This is the start of the frequency range for system calibration. A calibration data value will be created for this frequency. Start Frequency is limited to the intersection of the analyzer frequency range and the calibrator frequency range.

Stop Frequency - This is the stop of the frequency range for system calibration. Calibration data value are created at evenly spaced frequencies between Start Frequency and Stop Frequency. Stop Frequency is limited to the intersection of the analyzer frequency range and the calibrator frequency range. The frequency of the final calibration data value may not be exactly Stop Frequency because frequencies are rounded down to the resolution of the spectrum used in creating calibration data.

Points - This specifies the number of calibration data points to create at evenly spaced frequencies between Start Frequency and Stop Frequency.

Calibration data is created from measurements of a comb signal generated by the system calibrator. The minimum/maximum limits of Start Frequency, Stop Frequency and Points are dependent on the limits of comb frequency spacing of the system calibrator device.

Frequency Step Size - This is a read-only display of the nominal frequency spacing of calibration data values. The actual frequency step size is rounded down to the resolution of the spectrum used in creating calibration data.

Magnitude Flatness Threshold - This is the threshold, in dB, for magnitude flatness when verification is performed. Verification passes when worst-case deviation from mean magnitude is less than or equal to the magnitude flatness threshold and fails when greater than the threshold. Verification is performed when Calibrate and Verify are executed.

Phase Linearity Threshold - This the threshold, in degrees, for phase linearity when verification is performed. Verification passes when worst-case deviation from linear phase is less than or equal to the phase linearity threshold and fails when greater than the threshold. Verification is performed when Calibrate and Verify are executed.

Save Setup After Calibration - When this value is true, the current setup is saved to a file with the same base filename and folder as the calibration data file when Calibrate is executed. The setup file has a file extension of .setx, while the calibration data file has a file extension of .cal. When this value is false, no setup file is saved when Calibrate is executed. This value is true by default.

Calibration data is generally valid only for the analyzer setup in place when Calibrate is executed. Recalling the setup saved when Calibrate was executed loads and enabled the User Correction RF Calibration file created by Calibrate. Recalling the setup file is a convenient way to apply corrections using calibration data that is valid for the analyzer setup.

Worst-case Results - Displays the results of verification. Verification determines the worst-case deviation of magnitude from the mean magnitude and the worst-case deviation from linear phase in measurements of the system calibrator device for the specified number of points over the system calibration frequency range. Verification passes when worst-case results are within magnitude and phase thresholds and fails when results are greater than the thresholds.

Calibrate - System calibration is performed when clicked. Calibrate performs a series of measurements of the system calibrator over the system calibration frequency range. The results of these measurements are used to create calibration data which is saved to the calibration data file. When Calibration Disables Existing User Corrections is true, all RF Correction files are disabled before measurements are made. The states of RF Correction files are restored if Calibrate is canceled or fails. After Calibrate successfully completes the calibration file created is loaded as an RF Correction file and is enabled. A setup file is saved if Save Setup After Calibration is true. Verification is then performed. The results of verification are displayed under Worst-case Results and in the status bar below that.

Verify - Clicking Verify initiates verification of the current User Correction state. Verify performs a series of measurements of the system calibrator for the current value of Points over the current system calibration frequency range. This may not be the same frequency range or number of points that were used when User Correction files were created. Verify can be used to verify the results of Calibrate after time has elapsed or to verify validity of corrections to an analyzer setup that varies from the setup used when creating the calibration data.