A Broadband Rectangular Reentrant Cavity for Multiple-Beam Klystron

Broadbanding of a rectangular reentrant cavity is proposed through reducing its unloaded quality factor by loading the cavity with periodic rectangular ridges placed on cavity transverse walls and orienting them perpendicular to the electric field. The effect of ridge loading on the cavity parameters, namely, resonant frequency, unloaded quality factor, and characteristic shunt impedance was investigated through 3-D electromagnetic simulations. Ridge loading of the cavity could facilitate around 70% reduction in the quality factor without any change in resonant frequency and negligible change in characteristic shunt impedance of that of a no-ridge-loaded cavity. The simulated resonant frequency and quality factor of typical S-band rectangular reentrant cavities were validated against measurements.