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The slow-wave characteristics are described by considering space harmonics for confocal corrugated elliptical waveguides. The results have shown that the dispersion characteristics and the interaction impedance can be improved by changing the waveguide eccentricity.

Mode discriminators based on mode-selective coupling principle have a series of advantages. The designing method of this type of discriminator is presented in this paper. The emphasis is put on the mode-selective coupler with a multihole and muitigroup of coupling holes. All of the dimensions of the discriminator are determined by this method. The calibration and power measurement of the discriminator are also investigated. Some design examples of discriminators for 35- and 70-GHz gyrotrons, which can be applied to discriminate the T[E.sub.11], T[E.sub.01], and T[E.sub.02] modes and the T[E.sub.01], T[E.sub.02], and T[E.sub.03] modes, respectively, are given. Index Terms--Gyrotron, mode discriminator, mode-selective coupler, multigroup coupling.

As one of the important means in discriminating every mode in a high power microwave (HPM) multimode system, utilizing a mode-selective directional coupler to quantitatively analyze multimodes and power measurement has been proposed. The first step of this method is to calibrate the coupling coefficients of each coupled mode in the HPM system. Moreover, the conventional calibrating method must make the corresponding single mode exciter or mode generator. In this manuscript, a different calibrating method is presented by measuring the output power from each output port of two back-to-back identical mode-selective couplers, including the backward wave power, then the coupling coefficients of each coupled mode can be calculated by combining and solving equations. In this way, it is not necessary to manufacture the single mode exciter or mode generator for each mode in the HPM system, and also to repeat iteration solution; therefore, this method is more precise, convenient, efficient, and has lower cost than the current other methods. [ABSTRACT FROM AUTHOR]

Angular log-periodic meander line (ALPML) traveling wave tube (TWT) is one kind of low voltage miniature TWT. In order to decrease high frequency loss, avoid charge accumulation and enhance coupling impedance, the conformal microstrip ALPML TWT based on silicon substrate is proposed in this paper, which means that the projections of silicon supporting structure and metallic microstrip meander line are same in the top view. The microfabrication technology DRIE can be used to fabricate this structure. Compared with the conventional microstrip ALPML TWT, the coupling impedance of conformal microstrip ALPML TWT increases 50%. The particle-in-cell (PIC) simulation results reveal that the output power of conformal microstrip ALPML TWT can reach 220W at 35GHz, while the efficiency is 20%. The 3-dB bandwidth reaches 14GHz in the frequency range between 28GHz and 41GHz when the operating voltage and radial sheet beam current are 3600V and 0.3A, respectively. [ABSTRACT FROM AUTHOR]

An innovative complementary electric split-ring resonator metamaterial (MTM) structure applied as the slow-wave circuit for a cascade backward-wave oscillator (CBWO) operating in C-band is studied in this paper. The idea of a drift tube in a multiresonant cavity extended interaction klystronis borrowed to design a novel backward-wave oscillator (BWO). The construction of this device features two BWOs separated by a short cutoff waveguide for permitting the flow of the electronbeam and stopping the electromagnetic wave. The high-frequency characteristics are analyzed and optimized by using a high-frequency structure simulator and computer simulation technology (CST). Meanwhile, the S-parameter retrieval approach is used to retrieve the effective permittivity and permeability. In addition, the CST code is adopted to investigate the performance of the MTM-based CBWO. The particle-in-cell simulation results show that the novel CBWO is capable of achieving over 51.77% electronic efficiency from 4.8344 to 4.8687GHz. Meanwhile, the maximum electronic efficiency can reach 82.44%, corresponding to a peak output power of 14.51 MW at 4.8466 GHz. These results indicate that the MTM-based CBWO proposed in this paper has the characteristic of miniaturization, manufacturability, and high electronic efficiency. [ABSTRACT FROM AUTHOR]

A novel slotted helix slow-wave structure (SWS) is proposed to develop high power, wide-bandwidth, high reliability millimeter-wave traveling-wave tube (TWT). This structure, which can improve the heat dissipation capability of the helix SWS, evolves from conventional helix SWS with three parallel rows of rectangular slots made in the outside of the helix. In this paper, thermal stress analysis, the electromagnetic characteristics and the beam-wave interaction of this structure are investigated. The conclusions of this paper will be a great help for the design of millimeter-wave traveling-wave tube. [ABSTRACT FROM AUTHOR]

With instantaneous and in situ characteristics, mode discriminators based on mode-selective coupling principles attract much attention, but their working bandwidth is restricted by the distribution of the equal distance between adjacent holes and the equal radius of all holes. Meanwhile, the equal-interval and unequal-radius distribution of holes can increase the bandwidth of the mode discriminators remarkably. Therefore, the basic theory, designing method and example of the mode discriminators based on the equal-interval and unequal-intensity (i.e. various radii of holes) coupling are brought forward in this paper. The formulas of coupling intensity in terms of binomial distribution and Chebyshev distribution are also presented. The calculation shows that the working bandwidth of the mode discriminators based upon mode-selective coupling according to binomial distribution or Chebyshev distribution can reach 15% to 19%, which is twice over that of equal-interval and equal-intensity coupling mode discriminators. [ABSTRACT FROM AUTHOR]

Abstract  Elliptical waveguides and ridged waveguides have found broad applications in many microwave structures. The elliptical waveguide with double infinite thin ridges has been formulated using the mode-matching method. Exact closed-form expressions for eigenvalue problem of all TE and TM modes are presented. Numerical results suggest that the elliptical ridged waveguides have larger bandwidth than that of circular ones. [ABSTRACT FROM AUTHOR]

A simple but reasonable approach to the cold dispersion analysis of a coaxial arbitrary-shaped groove cylindrical waveguide is presented in the fast-wave regime for potential application in wideband gyro-traveling-wave tubes (gyro-TWTs). The unified dispersion equation of this structure is obtained by using an approximate field-theory analysis, in which the profile of the groove is approximately replaced by a series of rectangular steps, and the continued relation of the fields between two adjacent steps and the matching conditions at the interface between the groove region and central region are investigated. The dispersion characteristics of the disk-loaded structure obtained by modifying above results have been validated against those reported by Kesari et al. Meanwhile, the dispersion characteristics of arbitrary-shaped groove, such as the triangle-groove-loaded one are proved to agree well with Computer Simulation Technology (CST) Microwave Studio simulation. The results of numerical calculations of the dispersion relation shows that the adjustment of structure parameters led to the possibility of widening the straight-line portion of ω-β dispersion characteristics, which is required for wideband TWT performance in view of widening the bandwidth of resonance between the beam-mode and the waveguide-mode. Comparison of several different shape groove-loaded structures shows that the coaxial inverted trapezoid groove one shows the most potential application in wideband gyro-TWT because its transverse electric field is the greatest so that can interact effectively with the electron beam. [ABSTRACT FROM AUTHOR]

Abstract: The coaxial circular-arc-groove periodic slow-wave system for relativestic traveling wave tubes (RTWT) is presented in this paper. To analyze the field in the groove region, the continuous profile of the circular arc is approximately replaced by a series of rectangular steps and the field continuity at the neighboring steps is deduced. The dispersion equation of the coaxial circular-arc-groove slow-wave structure is derived by the matching conditions at the interface between the groove region and central region. The influence of various circuit parameters on the dispersion relation is investigated by the numerical calculation. [ABSTRACT FROM AUTHOR]

The coaxial ridged disk-loaded structure which is a new disk-loaded periodic system is presented and analyzed in this paper. As an all-metal slow-wave circuit, it has properties that can be used in high-power traveling wave tubes (TWT) and relativistic TWTs. The dispersion equation and coupling impedance of the structure are investigated in the first part of this paper. The results of numerical calculations of the dispersion relation and coupling impedance with different structure dimensions indicate that the interaction impedance of the ridged disk-loaded structure is higher than that of the disk-loaded structure without ridges in most frequency ranges. In the second part, the "hot" dispersion equation of this circuit with an annular electron beam is obtained according to a self-consistent linear theory. The influence of physical dimensions and beam parameters on the small signal gain is discussed. [ABSTRACT FROM AUTHOR]

Presents the designing method of the mode discriminator based on the mode-selective coupler. Emphasis on the mode-selective coupler with a multihole and multigroup of coupling holes; Calibration and power measurement of the discriminator; Design examples for gyrotrons.