Network Analyzer Calibrations - Yesterday, Today and Tomorrow

From the very beginning, network analyzers were calibrated manually. Grease pencils were used to mark the reference level on a CRT display or meter display. Such calibration methods were able to remove some of the measurement scalar errors. Full real time vector error correction wasn't possible until the introduction of the hp8540A automatic vector network analyzer. It also allowed imperfect standards, i.e. an open, to be defined by a device model. The short-open-load-through calibration method was fully enabled. Since then, a surge in research on vna calibration methods brought us the through-reflect-line family of calibrations. Electronic calibration was invented to simplify calibration. Multi-port, differential and non-linear calibration methods and standards are the current and future challenges.