Plasma effects of the directional coupler for high-power microwave measurements

摘要

The directional coupler is an important online power measurement device based on coupling principles. It is widely used for real-time monitoring of the performance of high-power microwave devices. However, insufficient power handling capacity limits further applications of the coupler in higher-pulsed energy measurements. From a theoretical and numerical analysis, the plasma effects of breakdown on the coupler are investigated. The plasma is found to break the fixed phase relationship between the coupling holes and eventually the directivity of the coupler. As the plasma density increases, the isolation of the coupler decreases rapidly, and thus, a negative power flux in the secondary rectangular waveguide increases gradually. Simultaneously, the positive power flux fluctuates and even terminates ahead of the microwave pulse in the main circular waveguide. The conclusions provide a good interpretation of the experimental phenomena. Published by AIP Publishing.