scikit-rf

scikit-rf reads and writes Touchstone S-parameter files, plots them on Smith charts and graphs, and lets you cascade networks, convert between parameter types and de-embed test fixtures. It includes offline network analyser calibration methods: SOL and SDDL for one port, and TRL, multiline TRL, SOLT and Unknown Thru for two ports, plus an interface to some VNA instruments, including NanoVNA. Engineers use it to process measurements, calibrate home-built test setups and characterise filters, amplifiers and antennas. Limitation: there is no graphical interface and the work is done in Python code, and instrument support varies by model.