Characterization of Metamaterial Slow-Wave Structure Loaded With Complementary Electric Split-Ring Resonators

We proposed an all-metal metamaterial slow-wave structure (MSWS) that consists of a circular waveguide periodically loaded with complementary electric split-ring resonators (CeSRRs). We set up an equivalent circuit theoretical model of MSWS and analyzed its high-frequency characteristics. Also, based on the surface current distribution on the CeSRR obtained by using the eigenmode solver in the CST Microwave Studio, a method of calculating the resonant frequency of the CeSRR was proposed. Furthermore, an MSWS with RF coupling port was designed, simulated, fabricated, and experimentally characterized. The dispersion characteristics of MSWS obtained by interpreting the experimental transmission characteristics agreed well with those predicted by theory as well as simulation. Based on the results of simulation and experiment, a concept of resonance-coupling was proposed for the passband of MSWS for frequencies below the cutoff frequency of an empty circular waveguide. The role of the slot-line in the CeSRR in influencing the performance of MSWS was also analyzed. The proposed MSWS has wide potential applications in vacuum electron devices, such as backward-wave oscillator and extended interaction klystron.