Design and Simulation of a Broadband $Ka$ -Band Gyrotron Traveling-Wave Tube With a Fully Dielectric-Loaded Circuit

This paper presents the design and simulation of a broadband
Ka
-band gyrotron traveling-wave tube operating in the
$\text {TE}^{d}_{\text {02}}$
mode at the fundamental cyclotron harmonic with a fully dielectric-loaded circuit. Through loading loss-free dielectric on the entire circuit, the dispersion properties of the circuit are changed to maintain resonance condition at a wide frequency band. A sliced lossy dielectric-loaded structure is employed to provide the required loss for stable operation. The interaction circuit is analyzed under the field matching theory, the nonlinear self-consistent theory, and particle-in-cell codes. A saturated peak output power of 100 kW is achieved at 29 GHz, corresponding to a saturated gain of 44 dB and an efficiency of more than 15% within a 3-dB saturated bandwidth of 6.1 GHz (20% relative bandwidth).