Analysis of Dispersion and Losses in Helically Corrugated Metallic Waveguides by 2-D Vector Finite-Element Method

Hollow metallic circular waveguides with helical corrugation of the inner surface (helical waveguides) attract considerable interest for various applications such as interaction regions in gyrotron traveling-wave tubes and as a dispersive medium for passive microwave pulse compression. In this paper, we employ a vector finite-element method in 2-D formulation for computation of the dispersion, attenuation characteristics, and the distribution of electromagnetic fields of eigenwaves of helical waveguides. As shown by comparison with the results of previously performed 3-D calculations, the presented method provides sufficient accuracy of calculating the characteristics of helical waveguides for a number of practically important cases at much lesser consumption of computer resources.

I. Introduction

Metallic structures of circular cross section with a helical corrugation of the inner surface (helical waveguides) are widely used in microwave high-power electronics. In particular, they are frequently employed as selective elements, such as mode converters and reflectors for waves of circular waveguides (see, e.g., [1]–[3]). Furthermore, helical structures are used or considered to be used as operating electrodynamic systems of various electronic devices [4], [5]. Currently, two areas in which the waveguides with helical corrugation play a key role are being developed most actively. The first area is the development of gyro-devices with a high level of continuous or average power and a wideband frequency tuning in the millimeter wavelength range [6], and the second is the creation of passive microwave pulse compressors for achieving multigigawatt power levels in - and -bands [7], [8].