Some advanced techniques for the measurement of a small phase-shift and the direct-reading measurement of phase-shifts

The accuracy of the measurement of a microwave phase-shift has been mainly restricted by a frequency fluctuation since the change of a microwave frequency causes a change in its phase in conventional methods. Therefore, in the measurement of a small phase-shift, most efforts have been devoted to the stabilization of the microwave frequency. The author has devised a new method by which a small phase-shift can be determined with a higher accuracy than what will be obtained in ordinary methods after a frequency stabilization is made by a factor of 10^-2 or more through an elimination of the effect of the frequency fluctuation. Next the author has improved the direct-reading method of phase-shifts so that the changes of the phase shift may be read and recorded directly and accurately with respect to an arbitrary variable relating to the change of the state of the sample under test. As results of experiments with trial equipment, the accuracy of about ±2π×10^-4 radians could be obtained by the former method and ±3π×10^-3 radians by the latter method under conditions of the frequency fluctuations of Δf/f_o ≃ 10^-4 order, by which the phase fluctuations of about ±2π×10^-2 radians were caused. It is promising to increase their accuracy by about a factor of 10^-2 or more by some improvements of the circuitry in the signal dealing system and by prevention of mechanical vibrations of the system. (author)