Magnetrons usually operate in the π mode, and the phase of the microwave electric field at the two adjacent resonator cavities is exactly 180 °, that is, the direction of the microwave field is opposite (Figure 2). Although the microwave field is a standing wave field, in the case of the? Mode, the equivalent of two identical microwave fields is moved in the opposite direction on the circumference, and the phase velocity values of the two fields are equal. The electrons emitted from the cathode move under the action of the orthogonal electromagnetic field. Adjust the DC voltage and the constant magnetic field so that the average drift velocity v = E / B in the circumferential direction is exactly equal to the phase velocity v of a microwave field moving in its direction (where E is the DC voltage generated by the DC voltage in the interaction space Field average, B for the axial constant magnetic induction), the electron can be synchronized with the microwave field movement. During the synchronous motion, the part of the electron in the microwave deceleration field will gradually give its own DC bit to the microwave field, and to the anode closer, and finally collected for the anode. This part of the electrons to the microwave field transfer energy, is conducive to the establishment of a stable microwave in the magnetron oscillation, it is called favorable electrons.