Phase lock of submillimetric backward-wave-oscillators

The phase lock of backward-wave-oscillators operating in the submillimeter range requires the reconsideration of some theoretical aspects in order to take into account the high operation frequency and the high flicker noise level of these sources. Experimental data referring to the frequency noise spectrum of a 600-GHz carcinotron are reported together with some guidelines for properly designing the control phase-locked loop. The results achieved in a practical realization are presented and compared to the theoretical considerations developed. The experimental results demonstrate the possibility of achieving a satisfactory signal-to-noise ratio and narrow linewidth in the phase stabilization of a 600-GHz carcinotron