The following example presumes an MS464xB Series VNA in a millimeter-wave or broadband setup so that W1 connectors can be used (since they represent a common triple offset short example). A different connector can be selected in Step 4 below if a different model/configuration is being used. It is assumed that a M-F cable is connected to Port 2 so that a M (port 1) and F (port 2) reference plane pair is available.
In this example, a full 2-Port SSST calibration will be performed although a number of other options are discussed along the way. These options are discussed in the Calibration Overview section.
1. Set the desired frequency range (FREQUENCY menu), power (POWER menu) and IFBW/Averaging (AVERAGING menu). The default power level varies depending on the instrument model and options, but will often be adequate for all passive and many active device measurements. The default IFBW is 1 kHz with averaging off, which is adequate for many applications.
2. Navigate to the TWO PORT CAL menu.
• MAIN | Calibration | CALIBRATION | Calibrate | CALIBRATE | Manual Cal | MANUAL CAL | 2 -Port Cal | TWO PORT CAL
Note
If a previous calibration exists, the Thru Update button will be active. See the Calibration Overview in Other Calibration Procedures for more information.
3. Select Modify Cal Setup, and on the CAL SETUP menu, select a Cal Method of SSST/SSSR and a Line Type of Coaxial.
4. Select Edit Cal Params, the TWO PORT CAL SETUP (SSST, COAXIAL) dialog box appears (shown below).
TWO PORT CAL SETUP (SSST, COAXIAL) Dialog Box (1 of 2)
1. Through selected allows user entries for length, line impedance, line loss and frequency.
2. Reciprocal selected allows user entry for length.
3. S2P Thru selected provides buttons for loading, viewing, and characterization (to generate S2P files).
5. In the TWO PORT CAL SETUP (SSST, COAXIAL) dialog box, set the following calibration components:
a. Reference impedance defaults to 50 ohms. This establishes the reference impedance for reference plane changes and Smith chart plotting but can be changed later on a per-trace basis.
b. In the Select Cal Type area, select the Full 2 Port radio button.
c. A zero-length (or mating) thru will be used so enter Through for the line, 0 mm for the length and 0 dB/mm loss. Zero can be entered for the reference frequency when no loss scaling is employed and the entered loss value is used for all frequencies. If a reciprocal network was being used instead of a through, the line selection would be Reciprocal and the length entered would serve as an estimate for root choice purposes.
If s2p thru was selected, the .s2p file describing the thru s-parameters would be loaded and used during the calibration. A 'characterize thru' option is also available using two previous reflection-only calibrations (with and without the thru element present) to calculate the .s2p file.
d. For Test Port 1, select a DUT connector of W1-Conn (F). The dialog box then displays a port connector as W1-Conn (M).
e. For Test Port 2, select a DUT connector of W1-Conn (M). The dialog box then displays a port connector as W1-Conn (F).
f. Click OK to close the dialog. Select Back at the bottom of the menu to return to the previous level and the TWO PORT CAL menu.
6. The Port 1 Reflective Devices and the Port 2 Reflective Devices buttons display the REFL. DEVICES PORT 1 and PORT 2 menus. The six reflection standards to be measured (Short 1, Short 2, Short 3 on each menu) will be displayed here along with the read-only fields showing the port connector choices. Connect each standard in turn, and then click the corresponding button. When all six are done (and six check marks appear), click Done to return to the previous level and the TWO PORT CAL menu.
7. After measuring all six reflection standards, connect the test cable to Port 1 to complete the zero length through. Click on the Thru/Recip button to display the THRU/RECIP menu where a check mark should appear after the sweep pair. Note that the displayed graphs change during this step as the instrument must measure all four S-parameters of the through line.
8. An optional isolation step is available but is not recommended. If desired, terminate Port 1 and the end of the cable attached to Port 2 before clicking on the Isolation (Optional) button and displaying the ISOLATIONS menu.
9. When all steps are successfully completed, the Done button is available where select returns to the CALIBRATION menu where the Cal Status button is set to ON.
10. Click Done. The calibration is now completed and turned on.
