A study of magnetron noise

The noise generated in the magnetron for microwave ovens was investigated experimentally. The observed noise exhibited a wide frequency spread: from several kilohertz to about 1000 MHz or more. The noise-generating mechanism was analyzed resulting in a hypothesis that the noise is mainly due to ions trapped in the vicinity of the cathode, and therefore comprises ion relaxation and ion plasma oscillations. The circulating motion of electrons in the magnetron interaction space also contributes to generation of the wide-frequency-band noise through intermodulation with the relaxation and plasma oscillations. Based on this assumption, experimental tubes were built with an ion drain electrode to prevent ion trapping. Experiments conducted with the experimental tubes revealed that ion drainage is an effective method for suppression of the magnetron noise.