What Is a Cavity Magnetron?

Multi-cavity magnetron is a kind of high-efficiency microwave electron tube that generates high-power ultra-high frequency oscillation. Mainly used in radar transmitters, microwave ovens and other high-power UHF oscillators.

Multi-cavity magnetron is a high-efficiency microwave that generates high-power ultra-high-frequency oscillations.

Figure 1 is

By the high-frequency electromagnetic field formed by magnetic and electric fields perpendicular to each other, electrons interact with the high-frequency electromagnetic field to generate microwave energy. The electrons are emitted from the cathode located in the center, induced by a Lorentz force to exhibit a spiral motion, and an electric field is applied to oscillate in its motion path, generating high-frequency radiation.

Multi-cavity magnetron radar

In the radar group, the waveguide of the magnetron is connected to the antenna. The magnetron operates with very short applied voltage pulses, which produces short pulses that radiate high-power microwave energy. As with all major radar systems, the radiation reflected from the target is analyzed to produce a radar map on the screen.

Several characteristics of the magnetron output make the radar problematic with this device. The first of these factors is the inherent instability of the magnetron's transmitter frequency. This instability not only causes a frequency shift from one pulse to the next, but also a frequency shift within a single transmitted pulse. The second factor is that the energy of the transmitted pulse is distributed over a relatively wide frequency spectrum, which requires the receiver to have a corresponding wide bandwidth. This wide bandwidth allows ambient electrical noise to be received by the receiver, thus blurring the radar echo slightly, thereby reducing the signal-to-noise ratio of the entire receiver. The third factor depends on the application and is the radiation hazard caused by the use of high power electromagnetic radiation. In some applications, such as marine radars installed on recreational ships, it is often found that radars with a magnetron output of 2 to 4 kilowatts are installed near the area occupied by passengers or passengers. In practical use, these factors have been overcome, or just accepted, and thousands of magnetron aviation and maritime radar devices are now in service. Recent advances in aeronautical meteorological lightning arresters and marine radars have successfully replaced semiconductor magnetron microwave oscillators with narrow output frequency ranges. These allow the use of narrower receiver bandwidths, and higher signal-to-noise ratios in turn allow lower transmitter power, reducing exposure to EMR. ^[3]

Multi-chamber magnetron heating

A magnetron for a microwave oven with a magnet in a mounting box. The horizontal plate forms a heat sink, which is cooled by the air flow from the fan. The magnetic field is generated by two powerful ring magnets, the lower of which is only visible. Almost all modern oven magnetrons have a similar layout and appearance.

In a microwave oven, the waveguide leads to a radio frequency transparent port and enters the cooking chamber. Since the fixed size of the chamber and its physical proximity to the magnetron usually produce a standing wave pattern in the chamber, an electric fan-shaped stirrer is placed in the waveguide to randomize the pattern. This is not always effective for larger objects in the room. Most modern microwave ovens also include a rotating table for food, called a turntable . ^[4]

Multi-cavity magnetron lighting

In a microwave excited lighting system such as a sulfur lamp, a magnetron provides a microwave field through a waveguide to a lighting cavity containing a luminescent substance (eg, sulfur, metal halide, etc.). Although efficient, these lights are much more complicated than other lighting methods and are therefore not commonly used. More modern variants use HEMT or GaN-on-SiC power semiconductors to generate microwaves that are essentially less complex and can be adjusted to maximize light output by using a PID system.