2.1.14. Vector network analyzer

2.1.14.1. What do I need before I start?

  1. VNA application requirements:

    • Personal computer (PC) running Windows or Linux.
  2. The following accessories and materials that are available in Red Pitaya store:

    • any kit that includes STEMlab 125-14 or 125-10 board
    • Vector network analyzer bridge module

2.1.14.2. Start using STEMlab as vector network analyzer

2.1.14.2.1. Connect vector network analyzer bridge to STEMlab

  • connect OUT of VNA module to STEMlab IN1
  • connect IN of VNA module to STEMlab OUT1
  • set IN1 jumpers on STEMlab to LV position

Coming soon: image that shows connections (trenutno vna bridge module connections.png).

2.1.14.2.2. Install & run network vector analyzer control app

2.1.14.2.2.1. Windows users only

2.1.14.2.2.2. Linux users only

  • Install Python 3 and all the required libraries:

    sudo apt-get install python3-dev python3-pip python3-numpy python3-pyqt5 libfreetype6-dev
    sudo pip3 install matplotlib mpldatacursor
    
  • Download and unpack the control program.

  • Run the control program:

    python3 vna.py
    

2.1.14.2.3. Type in the IP or URL address of the STEMlab board

2.1.14.2.3.1. Connect by entering STEMlab IP:

../../../_images/1_ip.PNG

To find our IP address of the STEMlab board first connect to STEMlab by following this instructions.

Then go to System->Network manager. IP is written next to label Address: xxx.xxx.xxx.xxx .

../../../_images/network_manager_icon.png

2.1.14.2.3.2. Connect by entering STEMlab URL:

../../../_images/1_url.PNG

2.1.14.2.4. Run vector network analyzer application on STEMlab.

../../../_images/vna_icon.png

2.1.14.2.5. Click Connect inside network vector analyzer control app.

../../../_images/2_connect.PNG

2.1.14.3. Perform calibration and start measuring

../../../_images/3_calibrate.PNG
  1. ) Connect SMA OPEN calibration connector marked with letter O to DUT SMA connector of the network vector analyzer bridge module. Click button “Open” and wait for calibration procedure to complete.

    ../../../_images/04_Calibration_O.jpg
  2. ) Connect SMA SHORT calibration connector marked with letter S to DUT SMA connector of the network vector analyzer bridge module. Click button “Short” and wait for calibration procedure to complete.

    ../../../_images/03_Calibration_S.jpg
  3. ) Connect SMA LOAD calibration connector marked with letter L to DUT SMA connector of the network vector analyzer bridge module. Click button “Load” and wait for calibration procedure to complete.

    ../../../_images/05_Calibration_L.jpg
  4. ) Select Smith chart tab at the bottom and then click Single button to perform a single measurement of the DUT. Dot in the middle of the Smith chart circle (@ 50ohm) will indicate that VNA is properly measuring reference 50ohm LOAD.

    ../../../_images/4-load_DUT_smith_chart.PNG
  5. ) Disconnect LOAD SMA connector and connect whatever DUT you’d like to measure.

    ../../../_images/07_Product_Combo.jpg

2.1.14.3.1. Examples:

  1. ) Measurement of 21m vertical antenna.

    Antenna is not well tuned (at freq. 14, 21MHz SWR should be <= 1.5)

    ../../../_images/antenna.png
  2. ) HAM RADIO 20m band bandpass filter

    SWR is better than 1.5 between start and stop band frequency. Filter load is around 50ohm between start and stop band frequency.

../../../_images/bandpass_filter.png ../../../_images/bandpass_filter_smith_chart.png

Credits

Original developer of the vector network analyzer STEMlab application is Pavel Demin.
Repositories used by our builds: