FM Distortion in Reflex Klystrons

The harmonic distortion introduced by a reflex klystron used as a frequency-modulated transmitter is computed. The method used is to make a power-series expansion of the theoretical expression of frequency as a function of reflector voltage, and then to relate the coefficients of the power series to the harmonic-distortion components. The design of a reflex klystron for low distortion is briefly discussed. A novel technique was used to measure the harmonic-distortion components experimentally. The experimental results were in good agreement with the theoretical predictions. The distortion is low enough for the reflex klystron to be useful for many transmitter and relay applications.