One-Port VNA Calibration: A Look Under the Hood (.PDF Download)

For a simple one-port vector-network-analyzer (VNA) calibration, only three error terms are needed: directivity (D), source match (S), and reflection tracking (R). These three errors theoretically appear between the VNA and the device under test (DUT). Knowledge of these three error terms allows for correction or calibration of the measurement.

Directivity error is mostly due to leakage in the bridge. Some amount of incident signal causes a small erroneous response on the reflection port. A typical raw bridge directivity might be anywhere from 15 to 40 dB. The source match represents the error in the source impedance of the VNA. The output source match is never perfect and is made somewhat worse by the cable connector and the test cable. A typical raw source match for a VNA might be 20 dB.