Abstract:
The aim of this work is study of high-frequency characteristics of planar meander-line slow-wave structures on dielectric substrates for millimeter-band traveling-wave tubes with sheet electron beam. The main method is numerical simulation of electromagnetic wave propagation processes in the mentioned structures using modern three-dimensional fully-electromagnetic finite-element and finite-difference software simulation packages. Results. For the microstrip slow-wave structure in addition to the main slow-wave mode there are fast volume modes, which can prevent stable regimes of TWT-amplifier operation. The spatial parameters of the structure were optimized to suppress the volume modes in the operating frequency band. High values of the attenuation coefficient of the surface slow-wave modes are also the features of the system. The results of the simulation of the ohmic losses using different numerical methods are presented, their qualitative and quantitative comparison is carried out. Conclusion. The high-frequency characteristics of miniaturized planar microstrip meander-line slow wave structures on a dielectric substrate are studied in detail. The effect of spatial parameters of the structure on the cut-off frequencies of volume and surface modes is investigated. The main methods of ohmic loss simulation are presented. It is shown that simulation using perturbation theory and time-domain simulation gives underestimated values of ohmic losses.
Keywords:vacuum microelectronic, planar microstrip slow wave structures, traveling wave tube, dispersion, interaction impedance, atttenuation coefficient, numerical modedilng of the electromagnetic waves, finite element method.
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