AN IMPROVED SLIDING-LOAD CALIBRATION PROCEDURE USING A SEMIPARAMETRICCIRCLE-FITTING PROCEDURE

Circle-fitting problems often occur in microwave engineering when deal ing with variable delays, e.g., during calibration using a sliding loa d, This paper proposes an efficient semiparametric circle-fitting proc edure, which takes into account the phase relationships over the frequ encies. It produces more accurate results than the standard sliding-lo ad calibration, requires only three positions on the sliding load for the whole frequency band, and is more robust to the settings of the po sitions of the sliding load, The proposed method also has the ability to detect whether or not the sliding load is defective or out of its s pecifications, This can be done by using only three positions on the s liding load, Optimal-position settings are then proposed, The performa nce of the proposed method is illustrated on sliding-load measurements up to 50 GHz, demonstrating the ability of detecting modeling errors and showing that the accuracy of the proposed method using three posit ions is comparable to the standard method with six positions.