Customization Theory of a Set of Optimal Calibration Standards for the Six-Port Reflectometer Based on Power Measurement Errors

A design theory of optimal calibration standards for a six-port reflectometer based on the power measurement error is proposed here. Rather than general, the calibration standards are specially customized corresponding to the practically utilized six-port reflectometer system itself. The basic logic is the objective stability of the six-port reflectometer in representing a reflection coefficient (Γ). Treated as devices under test, the calibration standards are customized as optimal corresponding to a power measurement condition during long-term and repeated usage. The availability of the customization is firstly verified in simulation. Γ around the entire Smith chart are calculated after different sets of calibration standards, respectively. The customized calibration is more accurate and distributes more concentrated. The effect is especially obvious for Γ with 0 dB to −15 dB in magnitude. A practical six-port reflectometer system is built and performed as the proposed method. By the replacement of the optimal calibration standards, the average of the worst-case range under long-term power measurement error is reduced from ±5.22 dB to ±3.50 dB in magnitude and from ±31.17° to ±19.18° in phase for |Γ| @−13 dB. More importantly, the probability with error larger than 15% in magnitude (|Γ| < −11.8 dB or |Γ| > −14.4 dB) is decreased from 27% to 16%. The proposed method is theoretically verified for a general working bandwidth of the built six-port (11.7%@2.55 GHz). The theory can be a plug-and-play and supplementary rule for most instrument based on multiport measurement to enhance the reliability and extend the lifespan.