Formulations of the basic vector network analyzer error model including switch terms

This paper explores details of the relationship between two expressions of the basic error model describing a two-port vector network analyzer (VNA). One of these formulations is the conventional twelve-term formulation; the other is in terms of error boxes. The paper focuses on the role of the switch terms. By fully detailing the relationship between the two formulations, the paper arrives at several significant new results, including an explicit constraint on the parameters of the twelve-term model.