Power limiting characteristics of a plasma-loaded evanescent-mode cavity resonator

Power limiting behavior of a cold plasma jet when introduced in an evanescent-mode (EVA) resonator is experimentally investigated in this paper. The plasma jet generates a pre-ionized region over the post of the cavity where most of the electric field is concentrated on. Due to pre-ionization, microwave breakdown occurs at a lower power level compared with the no-plasma case. During microwave breakdown the high electron density in the cavity causes high RF loss and consequently results in a power limiting behavior. The proposed technique has been examined in a 7.36-GHz EVA cavity resonator tested with incident power up to 56 W. Arc discharge occurs beyond 56 W causing high reflection levels of the RF signal. The proposed plasma-based approach can be employed in the future as a power limiting technology particularly in challenging applications where conventional techniques cannot be used due to temperature, power, or linearity constraints.