A K-band oscillator locked to the first water resonance

A Gunn diode oscillator has been locked to the rotational absorption line of water at 22235.170 MHz. The water in vapor form was obtained from atmospheric air. The air was held in a vacuum chamber which was inserted in a Fabry-Perot open semiconfocal resonator. A sinusoidal electric field, the Stark field, was impressed upon the gas in the cavity which is coupled to the Gunn oscillator, thus modulating the water vapor absorption of microwave energy. The second harmonic of the Stark Field was used to lock the Gunn oscillator. Working with the water spectral line (16/sub 16/-5/sub 23/) at 22.235 GHz, a frequency stability on the order of +or-50 kHz was achieved.<
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