Metamaterial-Inspired Backward Wave Oscillator Using a Dual Band Coaxial Coupler

A dual band metamaterial (MTM)-inspired backward wave oscillator (BWO) is developed by proposing a novel dual band coaxial coupler. The MTM-inspired BWO simultaneously exhibits dual band and miniaturization properties. The dual band property is confirmed by both transmission experiments and beam-wave interaction simulations. Meanwhile, the advantage of miniaturization results from the compact high frequency structure, i.e., its transverse and longitudinal sizes are about two-third smaller and slightly shorter than the previous BWO with the waveguide coupler, respectively. Further, the particle-in-cell results predict that the MTM-inspired BWO yields peak output powers of 114–137 kW at ~2.833 GHz and of 100–144 kW at ~4.527 GHz, respectively. Importantly, the power difference at the two frequencies is confined to ~1 dB, which is much smaller than that of the previous one with the waveguide coupler. These results confirm the feasibility of the compact dual band BWO, which might be applied to target recognition and plasma diagnostics.