In-situ Port Cal for Dual Carriages Tuner In-Situ port cal method is the calibration technique mainly for cascaded tuners or multi-carriage tuner. Unlike in-situ system cal which requires 2 VNA calibrations at 2 different planes, in-situ port cal only requires one VNA calibration at the VNA coax reference plane. Note: MT993H (harmonic tuning option) is required to use this feature. Step 1. Setting up block diagram in ATS 1. Launch ATS software version 5.31 or above 2. From the menu, select File Default. A default power block diagram with 2 tuners will show up. 3. To characterize source tuner, right click on the load tuner and select Disable. To characterize load tuner, right click on the source tuner and select Disable. 4. The block diagram will look like one of the below depending on either source or load configuration. 5. Double click on the green area around the tuner to open the tuner port control dialog. 6. Click on the Options tab and select tuning mode to Mode 3 Cascaded Harmonic Tuning. 7. Click on the Setup tab and enable Tuner 1 and Tuner 2, and select the appropriate tuner driver as shown below. For carriage 2, select TunLxiIP_C2.exe or TunLxiUSB_C2 depending on the type of connection between the PC and the tuner. For Carriage 1, select TunLxiIP.exe or TunLxiUSB.exe
For Dual carriage tuner, carriage 1 is always on the right side, and carriage 2 is always on the left side, regardless of source or load configuration, as long as the LCD display is on the front side facing the user. Carriage 2 Carriage 1 8. Enter the correct IP address (For dual carriage tuner, IP address will be the same for both carriage 1 and carriage 2 tuner) and click on Find Tuner. If the connection is OK, a message with Tuner Found will appear and the model number and serial number will be automatically entered. If the message with Tuner not found appear, then go back and double check the communication (see tuner manual for how to setup LXI tuner communication). 9. Once the tuners are setup, close the tuner port control dialog. 10. Now, add the VNA in the block diagram by selecting Setup Instruments from ATS menu. Instrument setup dialog will appear.
11. Click on the Network Analyzer and select the appropriate VNA driver, model number, and GPIB address. Leave the rest of the parameter as default. 12. Click on Test from the instrument dialog and make sure the VNA can be communicated through GPIB. Click OK and close all the dialogs and go back to the block diagram view. 13. In order for the VNA to show up, setup need to be changed to s-parameter configuration. Select Setup Sparameter Block Diagram from ATS menu and the VNA icon will appear in the block diagram view. 14. The block diagram is now setup and ready for calibration. Step 2. Calibration with ATS 1. From ATS menu, select Calibrate In-situ Port Cal. 2. From the dialog, select the port as either Source or Load depending on the actual configuration. Select Initialize Now and click Next.
3. Enter the frequency and IFBW and click Write new VNA frequencies. The new frequency list will get updated to the VNA. Go to the VNA front panel and perform 2-port calibration at the coax reference plane. Save the calibration as cset1.csa (for PNA model) after the calibration in order to use Speed enhancement feature. 4. Once the calibration is finished and saved, click Next on the dialog and select tuner characterization method. Adaptive modeling must be selected for cascaded tuners or dual carriage tuner. Also enabled Speed Enhancement and enter Calset to read as 1 (if VNA cal was saved as cset1.csa ). Temporary calset to write can be any number other than 1.
5. Click Next to select the frequency(s) to characterize the tuner. The tuner frequency must be a subset of VNA calibrated frequencies. 6. Click Next to select tuning range for both tuner 1 and tuner 2.
Point Seperation magnitude this number determine how dense the calibration points will be. The number is in gamma unit and the smaller the number, the denser the cal points. Maximum Phase step This number is to limit the maximum phase separation for each circle during the calibration. The lower the number the better the accuracy on interpolation. Minimum Probe Position This number determine how low the probe can be traveled to the center conductor. 0 is the absolute minimum and thus maximum reflection. Number of harmonic to control For dual carriage tuner, this number must be 2, since the tuner is capable of controlling both fundamental and second harmonic. The software then automatically determines either to use low frequency probe or high frequency probe at a given frequency to achieve optimum gamma at both fundamental and harmonic frequency. For single carriage tuner, this number is always kept at 1. Maximum harmonics to measure This can the harmonic frequency to be measured during the calibration. Up to 10 th harmonics can be selected, but VAN calibrated frequencies also need to be covered up to the same harmonics. 7. Next is to select the directory and the file name to be saved. Click on Auto name to select the directory and enter the file name. The file name will be automatically put in the appropriate fields. For tuner 1 (the tuner closest to the DUT), _Load will be added to the end of the file name for load tuner configuration (_Source for source configuration). For tuner 2 (the tuner away from the DUT), _Load2 will be added at the end of the file name (_Source2 for source configuration).
8. Once the file names are entered, click Finish and tuner calibration will begin. Once the calibration is finished, it will save 2 tuner file. _Load (or _Source) corresponds to tuner 1, which is the closest to the DUT. _Load2 (or _Source2) corresponds to tuner 2 which is the one away from the DUT.