Frequency qusai locking and noise reduction of the self-injection qusai locked magnetron

Abstract

Magnetrons are widely applied to the rapidly developing microwave industries as high power microwave sources. However, the free-running magnetron produces unstable frequency and wideband spectrum, which limits the magnetron's further applications for coherent power-combining and scientific fields. In this paper, by introducing a feedback loop with a high Q filter into the magnetron system, the output frequency can be qusai locked around the center frequency of the filter if the loop phase is between (2k-$\frac{1}{2}$)π and (2k+$\frac{1}{2}$)π. Moreover, the output frequency bandwidth of the self-injection magnetron is narrowed and the phase noise is also reduced. In order to find out the requirements for the qusai locked magnetron and the effects of the parameters on the qusai locked results, a theoretical model based on the combination of the equivalent circuit of the magnetron and the transfer function of the filter has been developed. Furthermore, numerical analyses illustrate the effect of the loop phase, Q value and the injection ratio on the output results. The experiments validate the conclusions obtained in the theoretical analyses.