Direct reading microwave refractometer

摘要

A microwave refractometer is disclosed which produces an output signal which varies as a linear function of the index of refraction of a microwave resonant sampling cavity. A voltage controlled oscillator having a variable oscillation frequency is electrically coupled to sampling cavity having a variable resonance frequency which is an inverse function of the index of refraction of the cavity. The resonant microwave electromagnetic signal present in the cavity is electrically coupled to a means which varies the oscillation frequency of the voltage controlled oscillator as a function of the resonant frequency and index of refraction of the sampling cavity. Means electrically coupled to an output signal of the voltage controlled oscillator produce an output signal which varies as a linear function of the index of refraction of the sampling cavity. In the preferred embodiment, this means comprises a crystal oscillator having a stable oscillation frequency and a circuit electrically coupled between the output of the voltage controlled oscillator and the crystal oscillator for gating and counting the number of cycles of the crystal oscillator which occur during a time interval which is a linear function of the index of refraction of the sampling cavity.