Analysis of the dispersion characteristics of the slow-wave structures used in the terahertz range devices
Models of slow-wave structures are used in simulating millimetre band devices are considered in the research. It is reasonable to use axially-symmetric slow-wave structures (SWS) for designing millimetre band traveling wave tubes (TWT). Simulating of considered slow-wave structure's 3D model produced in HFSS software package . The program that is outlined in  is used for calculation of dispersion characteristics. The model of slow-wave structure cell bases on the results of calculation. The nature of the distribution of the electromagnetic field in the system depends on the interaction features of electrons and the field in the TWT with slow-wave structure. The discrete approach described in  is the most common for solving this type of problems. It is electrodynamically justified to use difference equation for description of the discrete interaction in a traveling wave tube, in which the phase of the field in the interaction gaps in the longitudinal direction remains constant. The difference form of the electrodynamic theory of excitation allows to justify the use of one or another mathematical model for constructing a finite-difference equation . The coefficients of the finite-difference equation have a certain electrodynamic significance because they are calculated through the transmission matrix coefficients of the 2-N pole. Mathematical model of discrete interaction becomes more accurate when accuracy of coefficients of the finite-difference equation increases. In the research the 2-N pole is sextopole that appears form octopole in case of excitation current absence. The resulting sextopole is a mathematical model of the slow-wave structure cell. Coefficients of the obtained 2-N pole justifies accuracy, realism and recuperation of Electrodynamic characteristics of the simulated resonator slow-wave structure. Specification of discrete interaction processes in traveling-wave tubes, and electrodynamic processes in the SWS is ensured by the correct selection of the transmission matrix coefficients.
This paper considers the model of amplification of electromagnetic millimeter waves by non-relativistic electron beams in one-dimensional periodic electrodynamic systems. As slow-wave structures are investigated systems such as “winding waveguide” and “counter-pins”-type suitable for use in the millimeter range. The main directions of research are: - development of a traveling-wave tube model on the basis of the differential theory of excitation of electrodynamic systems by currents; - modeling and calculation for simplified waveguide-resonator model of electrodynamic properties of slow-wave structures such as "winding waveguide" in the millimeter range; - representation of a waveguide-resonator model of "winding waveguide"-type slow-wave structure, composed of segments of rectangular and U-shaped waveguide; - obtaining by a waveguide-resonator model coefficients of the transmission matrix, which allows to analyze the dispersion and coupling impedance in the band of amplified frequencies; - investigation of “winding waveguide"-type slow-wave structure taking into account the geometric phase rotation field in neighboring gaps by linear waveguide-resonator model represented by a chain of quadripoles by means of opposite switching of the induced current in the neighboring interaction gaps and also the first spatial harmonic used in traveling-wave tubes for the calculation of the dispersion; - calculation of a number of options that characterize the basic laws of changes in the properties of “winding waveguide"-type slow-wave structure; - modeling the properties of slow-wave structures such as "winding waveguide" using 3D-codes; - application of the results obtained using the 3D-codes as the numerical experiment to adjust waveguide-resonator model; - model building pin-type slow-wave structures using waveguide-resonator model, customized by experimental reference points. The paper shows that for modeling slow-wave structures such as “winding waveguide” and “counter-pins” waveguide-resonator model customized to the experimentally obtained reference points can be used. As the reference points can also be used the values of deceleration and the coupling impedance obtained by numerical experiment using HFSS. Waveguide resonator models constructed in such way are sufficiently accurate and simple. This paper shows that these models can be successfully used for the calculation of traveling-wave tubes operating in the millimeter range.
This paper describes concept of program complex’s composition which is used for traveling-wave tube (TWT) with resonator slow-wave structures and designing and implementating models for this complex. Projects of cm-range and mm-range TWT developed with program complex “VEGA” are presented.
A numerical simulator of the interaction processes in helical traveling-wave tubes is developed on the basis of the method of large particles in the 1D approximation with the use of the calculation methods developed previously. The output characteristics (frequency dependences of the output power and gain factor) of high-power traveling wave tubes based on helical slow-wave structures for operation in the C and Ku wave bands are studied theoretically and experimentally. It is shown that the results of numerical simulation are in satisfactory agreement with experimental data.
The developed model of cell slow-wave system type chains of linked resonators with adjacent channel filled with plasma, using the method of equivalent systems. This model represents the octal-pole, which is used for determination and calculation of electrodynamic characteristics. Calculations show that the introduction of plasma allows to extend the working width slow-wave system and increase the coupling impedance.
The electrodynamic characteristics of the helical slow-wave structure of a high-power pulse traveling-wave tube operating in the centimeter wavelength range are calculated by means of the solution of the dispersion equation and simulation. Special attention is focused on the effect of a helix wire profile on the electrodynamic characteristics of the system. The results of the theoretical study are compared with the experimental data.
Generalized error-locating codes are discussed. An algorithm for calculation of the upper bound of the probability of erroneous decoding for known code parameters and the input error probability is given. Based on this algorithm, an algorithm for selection of the code parameters for a specified design and input and output error probabilities is constructed. The lower bound of the probability of erroneous decoding is given. Examples of the dependence of the probability of erroneous decoding on the input error probability are given and the behavior of the obtained curves is explained.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.