The Working Principle of Magnetron in Microwave Equipment

The core component of microwave equipment is magnetron. Magnetron emits electromagnetic wave to absorb the material and raise the temperature. The anode resonance system of magnetron can not only produce the required electromagnetic oscillation, but also produce a variety of electromagnetic oscillations with different characteristics. In order to make the magnetron work steadily in the required mode, it is commonly used to isolate the interference mode by-quot; isolation band-quot; the isolation band connects the anode fins one by one, so as to increase the frequency interval between the working mode and the adjacent interference mode. In addition,

because the electrons after energy exchange still have a certain amount of energy, these electrons hit the anode to raise the temperature of the anode, the more electrons collected by the anode (i.e., the greater the current), or the higher the energy conversion rate of the electrons (the lower the energy conversion rate), the higher the anode temperature. Therefore, the anode needs to have good heat dissipation capacity. In general, the power tube uses forced air cooling, and the anode has radiators. High-power tubes are mostly water-cooled, with cooling water jackets on the anode. The cathode heating current is large, which requires the cathode lead to be short and thick, and the connection should be in good contact. The cathode lead of

high power transistor operates at a high temperature and is often forced to air-cooled to dissipate heat. The cathode is connected with negative high voltage when the magnetron works, so the lead part should have good insulation performance and meet the requirements of vacuum sealing. In order to prevent overheating of the anode due to electronic recoil, the cathode current should be reduced to prolong the service life of the magnetron after it works steadily. The cathode of magnetron, which is the emitter of electrons, is also a part of the interaction space. The performance of

cathode has a great influence on the working characteristics and life of the tube, and is regarded as the heart of the whole tube. There are many kinds of cathodes with different performances. Direct-heating cathode is commonly used in CW magnetron. It is made of tungsten wire or pure tungsten wire. It can emit electrons when the current is heated to a specified temperature. The cathode has the advantages of short heating time and strong resistance to electron bombardment, and is widely used in CW magnetrons.

Magnetron requires a strong constant magnetic field when it works normally, and its magnetic field induction intensity is generally thousands of gaussians. The higher the working frequency is, the stronger the applied magnetic field is. The magnetic circuit system of magnetron is a device that generates a constant magnetic field. The magnetic circuit system can be divided into two categories: permanent magnet and electromagnetism. Permanent magnet system is generally used for small power transistors. The so-called packaging type is composed of magnet steel and tube core. High-power tube uses electromagnet to generate magnetic field. The core and electromagnet are used together. There are upper and lower pole boots in the core to fix the gap distance. When the magnetron works, it can easily adjust the output power and working frequency by changing the magnetic field intensity. In addition, the anode current can be fed into the electromagnetic package to improve the stability of the tube.