Dual Band Metamaterial Cherenkov Oscillator With a Waveguide Coupler

We propose a waveguide coupler based on a metamaterial slow-wave structure (SWS) and then present a dual band metamaterial Cherenkov oscillator. The high-frequency characteristics of the SWS are studied by High Frequency Structure Simulator, indicating that both n = 0 space harmonic of fundamental mode and n = -1 space harmonic of first higher order mode exhibit "backward" wave properties and high interaction impedances. Meanwhile, the transmission property of the metamaterial SWS with the waveguide couplers is investigated. The simulation results show two passbands, which are verified by the experiment. In addition, we use linear theory to predict the starting currents, which are verified by Computer Simulation Technology (CST) Particle-In-Cell (PIC) simulation. Furthermore, the performance of the dual band metamaterial Cherenkov oscillator is studied using the CST PIC solver. The results show that the electronic efficiency of the proposed oscillator reaches 52% and its tuning bandwidths are ~7 and ~30 MHz for Modes 1 and 2, respectively. The CST PIC simulation results agree well with those using the Computer-aided highly efficient electromagnetic particle-incell code. These results indicate that the proposed oscillator has small size, dual band property, and high electronic efficiency.