Experimental Study on Spurious Suppression Techniques of S-band Magnetrons

Magnetrons are good candidates for large power microwave sources in various industrial applications. They are unstable oscillators with frequency and amplitude fluctuations, which easily cause electromagnetic interference (EMI) problems. Two regular methods to improve magnetrons' spectrum purity are compared in experiments using 1-kW S-band cook-type magnetrons. One method is to depress anode voltage ripple, which reduces the output frequency fluctuation range to 7.9%• The other method is injection-locking, which reduces the range to 1%. The injection-locking technique is more suitable for applications with requirements of high-frequency stability and controllability. Only low spurious noise and high-frequency purity are required in a few industrial applications. It is an economically feasible approach to depressing the voltage ripple by reducing filament current and adding a capacitor-based filter module. The study provides a reference to suppressing the EMI caused by magnetrons in different demands and scenarios.