Bulk Resonances in Slow-Wave Structures with High Ratios of Diameter to Radiation Wavelength

The program for numerical simulation of electrodynamic characteristics in large cross-sectional (overmode) slow-wave structures has been developed on the basis of the scattering matrix method. The program code allows studying electromagnetic fields of axially symmetric TM - and TE-modes of circular slow-wave structures (SWS) with the waveguide diameter-to-radiation wavelength ratio of about 4-50 in the frequency range of up to 0.5 THz. Detailed numerical investigations of dispersion characteristics of infinite periodic waveguides and electromagnetic eigenfields of TMon-modes for the finite length SWSs with the diameter-to-wavelength ratio equal to 4, 8, and 16 are presented. The cases of appearance of longitudinal bulk resonances and a region of stable maintenance of coupled waves TM01- TM0n in the finite length SWSs, depending on the height of diaphragms, are demonstrated. Based on the results of the simulation, the requirements to the accuracy of the geometric parameters of SWS, necessary to maintain the bulk resonance mode are identified.