I. Introduction
Scattering parameter (S-parameter) calibration of a vector network analyzer is essential and important for device/circuit measurements in high frequency applications. For production tests of radio-frequency integrated circuits (RFICs), the wafer probes in fixed positions for both of calibrations and measurements are usually preferred because of no movements required for probes in X-Y directions. In addition, the re-calibrations actually are performed often in production tests since the calibration accuracies will be degraded after certain probing times. The fixed probe design can further save the testing times and reduce the uncertainties come from the probe moving in X-Y directions.