Abstract
A stabilized microwave interferometer similar in principle to the classical Rayleigh refractometer is described. A model based on superheterodyne technique and phase detection at the intermediate frequency indicates that the information contained in the amplitude and phase can be extracted separately. In the actual circuit the overall noise figure is 15 dB and the dynamic range exceeds 160 dB in a 3 dB bandwidth of 0.66 Hz. DC drift limits the useful integration time to 100 s. Relative phase angles are determined within 2.0 degrees in the most disadvantageous case. Methods for suppression of leakage signals and a number of modifications of the interferometer approach are briefly considered.

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