Different measurement errors affect the results of VNA S-parameter measurements. The measurement errors can be divided into two categories:
•Systematic errors.
•Random errors.
Random errors are:
•Noise fluctuations and thermal drift in electronic components.
•Changes in the mechanical dimensions of cables and connectors subject to temperature drift.
•Repeatability of connections and cable bends.
Random errors are unpredictable and hence cannot be estimated and eliminated in calibration. Certain measures can be taken to reduce the random error:
•Proper source power selection.
•Narrower IF bandwidth.
•Constant ambient temperature.
•Proper warm-up time.
•Careful handling of connectors.
•Fewer cable bends after calibration.
•Sage of torque wrench to tighten the male connector nut and spanner to prevent the connected devices from rotation.
Systematic errors occur when the test setup components are not in ideal conditions. They are repeatable, and their characteristics do not change in time. Systematic errors can be calculated, and their value can be reduced mathematically by measurement results correction.
