Abstract: The present invention provides a novel measurement method for system parameters of a 5-port junction used in a VNA (Vector Network Analyzer). A VNA is a device for measuring amplitude ratios and phase differences (S-parameters: scattering matrix elements) between incident waves and reflected waves of a DUT (Device Under Test), or between input waves and transmitted waves. What has been newly discovered is that for 5 ports, S-parameters can be expressed by a linear coupling using H and power difference ratios ({P(S)/P(0)}?1). It is possible to easily calculate parameter H using a minimum of three already known standards, and amount of calculation can be reduced compared to conventionally.