ANALYSIS OF THE ELECTROMAGNETIC-WAVES IN AN OVERMODED FINITE-LENGTH SLOW-WAVE STRUCTURE

The electromagnetic fields of the higher order axial resonant modes in a slow wave structure are analyzed and found to have considerably dif ferent characteristics from those of the conventional fundamental mode . Here, the reflections at both ends produce axial resonant modes corr esponding to axisymmetric transverse magnetic (TM) modes. The period o f field modulation of some of the higher order axial modes is shorter than that of the usual mode in a cylindrical waveguide, which could be of practical interest for higher power, higher frequency operation of backward wave oscillators, A perturbation technique is used to ascert ain the field distribution inside the resonant cavity, and the numeric al results thus obtained are compared to some experimental data.