Dispersive characteristics and longitudinal resonance properties of trapezoidal corrugation coaxial slow-wave structure

The method for calculating the expression of the trapezoidal corrugation slow-wave structure (SWS) is studied in detail, which uses Fourier series expandedness. The dispersion curves of the two lowest symmetry TM0n waves are obtained with numerical calculation. Moreover, longitudinal resonance properties of the finite-length coaxial SWS are investigated with the S-parameter method. It is proposed that the introduction of a well designed coaxial extractor to slow-wave devices can reduce the period-number of the SWS, which not only can make the devices more compact, but also can avoid destructive competition between various longitudinal modes. Based on the theoretical study, a compact L-band coaxial relativistic backward wave oscillator is designed using the 2.5 D particle simulation code. S