Since version 1.9.6 the MCS supports a new feature for fine-calibration of Spectran devices, the so-called Matrix Calibration. As the name implies it allows to specify an offset for basically any frequency/value coordinate to compensate for device-specific deviations from the actual signal level.
To generate such a matrix with minimum effort you need two reference traces: one with the known signal level and one with the regular Spectran data. The first can be easily created manually with the MCS matrix calibration editor, the second can be obtained directly from the MCS by using the existing maximum, current or average traces, or loading a previously saved reference trace. You can even include several such pairs in a single matrix to define different offsets for different power levels.
To generate a matrix calibration just follow these steps:
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Setup the desired measurement parameters in the MCS
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Open the “Calibration” control in the MCS
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Click the “Open Matrix Editor” button
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In the new window, click “Add new Data source“
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Select the newly created cell in the “Reference Trace” column in the top-left area of the editor window
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Click “Add entry” in the lower-left section to add a new datapoint to the reference trace
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Enter the known frequency and power levels of your signal source in the created cells of the lower table
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Repeat step 6+7. If you have a fixed power level over the whole frequency range you only need two entries at the start and end frequencies, otherwise you can define as many intermediate points as needed. The editor will interpolate power levels between frequency points.
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Select the empty cell in the “Measurement Trace” column in the upper table
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Click “Load Trace” in the lower-left section to load either a previously stored reference trace or one of the current Spectran traces. The lower table will show the actual values and the difference to the previously defined reference trace at each frequency. Both traces will also be shown in the preview window on the right side.
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Click “Update Matrix” to generate the actual offset matrix. Depending on frequency range and the number of points in both traces this can take a few seconds or more.
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If you click “Enable Matrix Calibration” in the lower-right section of the window you can now see the effect of the calibration.
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Click “Save Setup” to store the matrix calibration for later use
Please note that the matrix calibration does have some restrictions:
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The Spectran may behave differently on different measurement settings, so the calibration is only valid when using the same settings as used for the reference trace
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The MCS peak suppression may interfere with the matrix calibration. This may cause internal electronic interference to show up when using the matrix calibration.
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It requires a known power-level over the whole frequency range to work. In the future a automatic calibration with our upcoming signal generator is planned but not available yet.