Investigation of High-Power Ring-Bar Traveling Wave Tube With Metamaterial Absorber

A rectangular split resonant ring (RSRR) metamaterial absorber (MMA) was proposed to suppress backward wave oscillation (BWO) in a ring-bar traveling wave tube (RB-TWT). The unit structure parameters of the RSRR were optimized to maximize the absorption of backward waves. The amplification performance of the proposed slow wave structure (SWS) was also carried out by using particle-in-cell (PIC) simulations. With an input power of 0.125 W, the operating bandwidth of the RB-TWT loaded with RSRR-MMA was 8-13 GHz, which was higher than that loaded with centralized attenuators (CAs; 8-11.5 GHz). The output power exceeded 5 kW with a gain of 46 dB in the range of 9.1-12.7 GHz. Furthermore, its saturated output power exceeded 5 kW, the saturated gain was over 41 dB, and the saturated electronic efficiency was more than 14.5% over the entire working frequency range of 8-13 GHz. Therefore, the RB-TWT with RSRR-MMA achieved a wider bandwidth compared with that of the RB-TWT with CA, where exhibits the potential application of RSRR-MMA in high-power vacuum electronic devices.