This paper describes how to suppress interference modes in coaxial magnetrons and how to choose a suitable inner cavity resonant frequency. A new method of suppression of interference modes is suggested. In order to separate the high and low branches of resonant frequencies of different modes in the inner cavity

a "rising sun" cavity structure is used. The cold properties of the inner cavity are analysed

measured

and compared with those in a co mmon coaxial magnetron. The method of computer-aided design for the cavity is also given.