LINAC2026 - 33rd Linear Accelerator Conference

Theoretical and Experimental Study of Resonant Frequency Shifting for Various Spark Gap Distance in Active Microwave Pulse Compressors

Not scheduled

2h

Daejeon Convention Center

Poster Presentation MC4.A06: RF power sources and power couplers Poster Session

Speaker

Taekheon Kim (National Security Research Institute)

Description

Microwave pulse compressors(MPCs) are used in linear accelerator RF systems to enhance peak power, as well as in other high power RF application such as IEMI testing. This paper presents a theoretical and experimental study on a low-power active MPC employing a spark gap switch. In particular, the change of resonant frequency as a function of spark gap length in an active MPC structure employing a self-breakdown type is investigated. During the charging time, the input impedance of the side arm of H-plane T-junction varies with spark gap distance, leading to a shift in the resonant frequency of MPC. In this work, this effect is modeled using an equivalent variable-length cylindrical post, and the resulting change in resonance condition with respect to gap length is analytically formulated. The proposed model explains the resonant frequency shift based on the variation of effective reactance in the side arm tee. To validate the model, an experimental setup based on a WR650 waveguide was constructed, and S-parameter was measured for various gap lengths. The results show a frequency shift with respect to gap length, which is good agreement with the equivalent circuit model.