Measurement of the radiation frequency of a pulsed submillimeter-wave gyrotron using beat-note signals with the harmonics of a millimeter-wave frequency synthesizer

A method of frequency measurements of pulse signals in the millimeter/submillimeter wavelength region, including signals with a pulse duration shorter than 10 μs and a repetition rate of 0.1 Hz, is considered. This method is based on the analysis of amplitudes of beat notes between the signal under study and radiation of a millimeter-wave frequency synthesizer. Application of this method to frequency measurements and identification of modes of a pulsed relativistic gyrotron in a configuration of a large-orbit gyrotron operating at three lower harmonics of the cyclotron frequency in the range 100–400 GHz is demonstrated. This method allows radiation-frequency measurements with an accuracy corresponding to the frequency instability during an oscillation pulse. It is shown that the method developed is also applicable to investigations of the oscillation dynamics within a single pulse.