Abstract
In this paper, we clarify the duplicated electromagnetic characteristics between the proposed two-beam overmoded multi-gap structure published in the paper titled “Tractable resonant structure with two nonuniform beams for a high-power 0.22-THz extended interaction oscillator” [Bi et al., IEEE Electron Device Lett. 42(6), 931–934 (2021)] and conventional multi-gap structures from the physical concept point of view. The replacement of the TE10 mode by the TE30 mode used in the interaction gaps provides the basis for the duplicated electromagnetic field distributions and frequencies between the two structures. The concept of magnetic coupling is proposed to support the resonant condition that supports duplication of the TE30 field and the frequency of the single-gap structure into the periodic standing-wave field of the multi-gap structure. With this concept, the perturbation of different axial phase shifts across one period to the standing-wave field of the TE30-0 mode is analyzed to clarify the profiles of the dispersion curves of the TE30 mode in the overmoded structure and the TE10 mode in the conventional structure. To demonstrate the profiles, a 220-GHz overmoded and conventional structure with nine gaps is designed, and their dispersion curves are obtained by using eigenmode simulations. In addition, the effect of the difference in the boundary conditions of the geometries of these two structures on the magnetic field distribution is analyzed to demonstrate the duplication of the ohmic losses between the two structures. The physical analysis in the duplicated electromagnetic characteristics lays a foundation for the promising design of the overmoded structure with two beams for high frequency extended interaction oscillators.
Highlights
Millimeter wave and terahertz science and technology is the core technology in many applications, including high-data communication, radar, and material testing
Extended interaction devices (EIDs) are more attractive in achieving high power and high efficiency because they combine the advantages of klystrons and traveling wave tubes
When the frequency is increased from millimeter wave to higher frequencies, the area of the cross section of EIDs is decreased due to the limitations in the operating wavelength
Summary
Millimeter wave and terahertz science and technology is the core technology in many applications, including high-data communication, radar, and material testing. The Ez field across the gaps of the TE30 and TE10 mode with different axial phase shifts is determined by the periodicity of the gaps and distribution of the magnetic coupling in the coupling cavities The phase differences between the 2π/9, 3π/9, and 0 modes are the smallest, and the perturbation to the Ez field of the 0 mode based on these phase differences is the smallest It is predicted from the equivalence of the frequency and field distribution of the TE10-0 and TE30-0 modes shown in Fig. 3 that there exists an overlapped region in the dispersion curves around the phase shift of 0 of the TE10 mode in the conventional structure and the TE30 mode in the overmoded structure.
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