We propose a coaxial line structure for phase-locking between magnetrons in the S-band for the first time. In this structure, two magnetrons operating in the π-mode are tightly coupled by the coaxial line. The design of a coaxial line structure, independent of physical dimensions, solves the problem of a ridge waveguide or rectangular waveguide being unsuitable for phase-locking in the compact S-band magnetron, as proposed by previous researchers. In addition, the phase relationship of the magnetron output signal in the phase-locked state can be switched between 0 and the π phase difference without changing the length of the coaxial line. Therefore, this design widens the frequency range used by mutual coupling phase-locked technology and allows switching of the phase relationship in an output signal without the need for additional equipment or physical space. After design simulation, two magnetrons achieved high-efficiency phase locking at a frequency of 2.415 GHz, with a phase-locked efficiency of 99.8%.
