Choice of calibration equations of the TSM method

For the reciprocal test fixtures, there are six independent S-parameters to be determined, and the thru-short-match (TSM) calibration can provide eight calibration equations. In this paper, the relation of calibration equations is investigated. It has been shown that the four equations obtained from the measurement with a transmission standard can be used simultaneously in the calibration. Experimental results show that the different choice of equations will lead to quite different solution, and the calibration accuracy can be improved by taking advantage of the established relation among the calibration equations and properly choosing calibration equations.