RF Calibration

Each user calibration type has a variety of implementations. Which method you use depends on the DUT, test system, and measurement requirements. The following four methods are commonly used in network analyzer calibration.

• Automatic Calibration (AutoCal)
• Short-Open-Load-Through (SOLT) Calibration
• Short-Open-Load-Reciprocal (SOLR) Calibration
• Through-Reflect-Line (TRL) Calibration

Standard Calibrations

With user calibration, various standards are used to calibrate the number of discrete frequency points configured for the sweep. Refer to the NI-VNA LabVIEW and C/CVI Reference sections for information about how to configure the frequency range and number of frequencies for the sweep.

Changing some NI-VNA settings after running a calibration invalidates the calibration. These settings include the following NI-VNA properties and attributes, which are described in more detail in the NI-VNA Programming section of this help file.

• IF bandwidth
• Source power
• Averaging type
• Frequency sweep characteristics
• Measurement enabled properties/attributes
• Calibration type
• Port connector gender and type
• Most AutoCal module properties/attributes

The one-port calibration is a short/open/load (SOL) calibration that removes source match, directivity, and frequency response errors. The one-path two-port calibration is a short/open/load/through (SOLT) calibration. Full, two-port calibrations can be completed with a through-reflect-line (TRL) calibration or a short/open/load/through (SOLT) calibration. Both TRL and SOLT calibration remove transmission response errors and transmission source match errors in addition to reflection error terms. You can also perform a reflection response calibration or a transmission response calibration, which corrects the frequency response of the respective path. Reflection response calibration requires an open connected to PORT 1, and transmission response calibration requires a through standard connected between PORT 1 and PORT 2.

Note  Reduced measurement accuracy may occur if you use a one-path two-port calibration instead of a full two-port calibration, because the one-path two-port calibration does not account for the load match of port two.

The following figure provides a state diagram for the NI-VNA calibration process.

For information about how to complete a calibration of your NI-VNA device using the NI-VNA SFP, refer to Performing an Automatic Calibration (AutoCal) Using the NI-VNA SFP, Performing a Manual Calibration Using the NI-VNA SFP, or Performing a User Calibration Using the NI-VNA API.

Calibration and Correction

When the device has a valid calibration, you can choose whether to "correct" the measurements by understanding the relationship between enabling correction and the calibration. This relationship is shown in the following table.