Fringe jump compensation techniques for the time-averaging zero-crossing phase measurement in the KSTAR millimeter-wave interferometer.

ABSTRACT

A fringe jump compensation algorithm has been developed for a phase measurement that measures the phase within a single fringe. The algorithm is extremely useful in the case of the time-averaging zero-crossing phase detector on noisy environments. When the noise level on the measurements is not sufficiently suppressed, the signals near the fringe jump show a negative slope instead of a sharp drop. The slope brings an ambiguity over the compensation process. An algorithm with an additional channel that measures the phase of a half fringe shift has been applied in the millimeter-wave interferometer on the Korea Superconducting Tokamak Advanced Research device. These techniques removed the ambiguity in most cases. The algorithm can provide a most simple, robust, and cost-effective solution for the phase measurement system in various fields.