Reference Level Port Extension

The reference plane used for DUT measurements and the blind mate interface may not be the same. There may be additional cables, adapters, or load boards between where the calibration is performed and where the DUT is connected. To achieve the appropriate dynamic range for the selected reference level at the DUT interface, you should use the reference level port extension.

To get optimal dynamic range at the DUT interface, you must characterize the S-parameters of the paths that go from the blind mate to the calibration reference plane. These paths are considered two-port networks, so reference level port extension is achieved by providing NI-RFPM with an S-parameter (S2P) file, which relates the blind mate reference plane to the calibration interface for each port in the system. In most cases, the same S2P file that is used for configuring NI-RFSG de-embedding should be used for reference level port extension. Otherwise, if the loss of the network is significant, there is a risk of ADC overflow, at which point, NI-RFPM will return an error.

You can use the NI-RFPM Create Reference Level Port Extension S-parameter Table (S2P file) VI or the niRFPM_CreateReferenceLevelPortExtensionTableFromS2PFile function to load the S-Parameter file into the NI-RFPM session. To enable the use of a reference level port extension S-parameter Table for a specific measurement port, you must call the NI-RFPM_Select_Reference_Level_Port_Extension_Table VI for that port. Refer to the example at the following location for more details: Start»All Programs»National Instruments»NI-RFPM»NI-RFPM Examples»RFPM_TwoPortSParameterMeasurementWithReferenceLevelPortExtension.vi .

If the quality of the reference level port extension S2P characterization file is inaccurate, it is possible that the dynamic range of the measurement could be suboptimal or ADC overflows could occur.