Models of rectangular and axially symmetric resonator slow-wave structures, which are built using transmission matrix for determining the characteristics of the slow-wave structures in different operation modes, are investigated. Elements of the transmission matrix are determined from the results of 3D simulation with the use of the HFSS software. In the analysis of the dispersion characteristics, slow-wave structures with two microwave propagation channels are studied and simulated using a 4×4 transmission matrix.
Original Russian Text © N.P. Kravchenko, S.V. Mukhin, S.A. Presnyakov, 2017, published in Radiotekhnika i Elektronika, 2017, Vol. 62, No. 7, pp. 693–702.
The results of this study were reported at the 2nd All-Russia Conference on Problems of Microwave Electronics, Moscow Institute of Electronics and Mathematics, Higher School of Economics (National Research University), Moscow, October 26−28, 2015.
For more than 60 years, the Anderson–Darling test is most frequently used among all Cramér–von Mises (omega-square) tests. This statistic modifies a classical empirical process defined within the [0, 1] interval by multiplying it by weighting function ψ(t) = (t(1–t))–1/2. The weighting function redistributes the test sensitivity to deviations of the distribution function of the observed stochastic quantity from a hypothetical distribution function in different its segments. However, the tests with other weighting functions may also be of interest in practice. New formulas for the eigenvalues of the Anderson–Darling statistic are proposed. The statistic “inverse” to the Anderson–Darling statistic with weighting function ψ(t) = (t(1–t))1/2 is considered. Tests with other weighting functions may also be of interest when weighted Cramér–von Mises statistics are used. The table of quantiles of statistics with weighting functions ψ(t) = tα(1–t)β, α >–1, β >–1 is presented. The quantiles are given for 36 different combinations of parameters α >–1 and β >–1. The table was calculated using accurate numerical methods and without application of modeling techniques.
The development of wireless communication technologies attracts increased interest to scenarios that impose severe restrictions on data transmission reliability and latency. Such scenarios include real-time applications, such as industrial automation, remote control, video streaming, and virtual reality. It is very difficult to satisfy the requirements imposed on the quality of service with the currently widespread communication technologies. Specifically, it is currently impossible to guarantee a low delay in Wi-Fi networks due to some peculiarities of the applied channel access methods. In this work, we study an approach that provides a low latency and high reliability of communications in Wi-Fi networks on the basis of an additional radio air interface. This approach is studied using the mathematical model of a heterogeneous network, which consists of devices that generate prioritized and non-prioritized data packets. The results of studies show that this approach provides the ability to satisfy the requirements of real-time applications, when certain restrictions on the intensity of prioritized traffic are met. In this case, a decrease in the throughput for non-prioritized traffic is insignificant.
This paper deals with the irregular binary low-density parity-check (LDPC) codes and two iterative low-complexity decoding algorithms. The first one is the majority error-correcting decoding algorithm, and the second one is iterative erasure-correcting decoding algorithm. The lower bounds on correcting capabilities (the guaranteed corrected error and erasure fraction respectively) of irregular LDPC code under decoding (error and erasure correcting respectively) algorithms with low-complexity were represented. These lower bounds were obtained as a result of analysis of Tanner graph representation of irregular LDPC code. The numerical results, obtained at the end of the paper for proposed lower-bounds achieved similar results for the previously known best lower-bounds for regular LDPC codes and were represented for the first time for the irregular LDPC codes.
The method of equivalent systems is used to simulate resonator slow-wave structures of beamplasma devices. A collisionless plasma is considered as a filler for the drift channel. The adequacy of the model is shown by comparing the calculation results with known experimental data. The dispersion characteristics of slow-wave systems are analyzed. The structure of the high-frequency unit of a beam-plasma traveling wave tube is developed, and the parameters of the tube are evaluated using the VEGA code.
Dispersion characteristics are calculated and the design is described of the slowing structure with ceramic-metal supports for a high-power ultrawideband traveling-wave tube. Experimental dispersion characteristics (measured in a frequency band of one-and-a-half octaves) of two types of helical slowing structures are obtained for different heights of lateral fins of the metal support holder. Theoretical results are compared with experimental data.
Exchange interaction of electron and positron bunches is simulated using the particle-in-cell method and macroscopic electron and positron wave functions. It is shown that a periodic exchange process with low or high nonlinearity is realized during variations in the electron and positron concentrations.
In this paper, we studied the phonetic approach for voice processing. A method for automatic recognition of speech signals, in which each quasistationary segment is associated with a fuzzy set of phonemes, was developed. We proposed the operation of the probabilistic triangular norm for fuzzy sets corresponding to the input frame and the nearest reference phoneme. The developed method was experimentally shown to allow a 1.5–5% reduction in the probability of erroneous recognition in comparison with known analogues.
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.
A words phonetic decoding method in automatic speech recognition is considered. The properties of Kullback–Leibler divergence are used to synthesize the estimation of the distribution of divergence between minimum speech units (e.g., single phonemes) inside a single class. It is demonstrated that the minimum variance of the intraphonemic divergence is reached when the phonetic database is tuned to the voice of a single speaker. The estimations are proven by experimental results on the recognition of vowel sounds and isolated words of Russian language.
A words phonetic decoding method in automatic speech recognition is considered. The properties of Kullback–Leibler divergence are used to synthesize the estimation of the distribution of divergence between minimum speech units (e.g., single phonemes) inside a single class. It is demonstrated that the min imum variance of the intraphonemic divergence is reached when the phonetic database is tuned to the voice of a single speaker. The estimations are proven by experimental results on the recognition of vowel sounds and isolated words of Russian language.
A design of a band-stop frequency-selective surface based on a planar mushroom-shaped metamaterial with an electronically tunable stopband has been proposed and investigated. The results of numerical simulation and experimental measurements of the parameters of a finite section of the metamaterial with mounted varicaps are presented. These results illustrate the shift of the structure stopband occurring simultaneously with a change in the capacitance of the lumped elements. Frequency dependences of the inherent dielectric parameters have been obtained. They indicate the presence of negative values of the effective permittivity and effective permeability of the proposed structure and the presence of the surface impedance that significantly exceeds the free-space characteristic impedance and is frequency-tunable.
Methods for extension of the rejection band of microwave devices on the basis of planar modified mushroom-shaped metamaterials comprising either two-layered topological structures with frequency-selective surfaces or multilayer bulk structures with intermediate layers containing split-ring resonators are proposed. Computer simulation of such devices, clearly demonstrating a twoto six-fold extension of the rejection band is performed. Experimental results confirming the results of numerical simulation are presented.
The dependence of the noise equivalent temperature difference (NETD) of a superconducting integrated receiver (SIR) on the receiver noise temperature and the inputsignal level has been investigated. An unprecedented NETD of 13±2 mK has been measured at a SIR noise temperature of 200 K, intermediate-frequency bandwidth of 4 GHz, and time constant of 1 s. With a decrease in the input signal, an improvement in the NETD is observed. This effect is explained by a reduction in the influence of the instabilities of the receiver power supply and the amplification circuit that occur when the input signal is decreased.