Metamaterial-based resonant structure for miniaturized low-frequency relativistic magnetrons

This paper introduces a metamaterial (MTM)-based resonant structure and applies it to relativistic magnetrons (RMs) with an all-cavity axial extraction technique. The MTM structure is designed to overcome the size limitations of conventional RMs and enable π-mode operation below the cutoff frequency of traditional structures. High-frequency analysis confirms the double-negative characteristics of the MTM structure, enabling π-mode operation below the cutoff frequency. Particle-in-cell simulation of CST was employed to compare the performance of the MTM RM with a state-of-the-art traditional design under an identical operating condition. Consequently, for L-band designs, the MTM RM achieves a significant reduction in volume, the radius being 70% of the traditional design, leading to approximately a 50% volume reduction, while other performance metrics such as operating current, startup time, saturation time, output power, efficiency, and frequency are nearly the same as the traditional RM. The study thus validates the potential of MTMs in enhancing the performance and miniaturization of RMs without compromising efficiency or operational mechanisms.