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Том 60, № 1 (2017)
- Год: 2017
- Статей: 8
- URL: https://ogarev-online.ru/0033-8443/issue/view/15155
Article
Features of HF Radio Wave Attenuation in the Midlatitude Ionosphere Near the Skip Zone Boundary
Аннотация
We briefly describe the history of studying the decameter radio wave attenuation by different methods in the midlatitude ionosphere. A new method of estimating the attenuation of HF radio waves in the ionospheric F region near the skip zone boundary is presented. This method is based on an analysis of the time structure of the interference field generated by highly stable monochromatic X-mode radio waves at the observation point. The main parameter is the effective electron collision frequency νeff, which allows for all energy losses in the form of equivalent heat loss. The frequency νeff is estimated by matching the assumed (model) and the experimentally observed structures. Model calculations are performed using the geometrical-optics approximation. The spatial attenuation caused by the influence of the medium-scale traveling ionospheric disturbances is taken into account. Spherical shape of the ionosphere and the Earth’s magnetic field are roughly allowed for. The results of recording of the level of signals from the RWM (Moscow) station at a frequency of 9.996 MHz at point Rostov are used.
1-11
A Possibility of Determining the Optical Peoperties of Water from the Snell-Window Image
Аннотация
We develop an analytical model of the Snell window, which allows for the effects of absorption and multiple scattering of light in water. The effect of an abnormally weak dependence of the visual brightness of the Snell-window boundary on the water turbidity is revealed. This effect, along with the effect of the Snell-window boundary “blurring” because of the light scattering in water can be used to determine the absorption and scattering coefficients of water using the corresponding processing of the Snell window images. We propose and experimentally check the algorithms for determining the inherent hydrooptical characteristics from the Snell-window images using the empirical correlations between various characteristics.
12-23
Solution of the Electron Motion Equations in a Relativistic Planar Magnetron
Аннотация
We have ascertained the influence of relativism on the processes and output parameters of a relativistic magnetron. The solution of the electron motion equations in a relativistic plane-geometry magnetron is presented. It is shown that these equations have the form corresponding to the nonrelativistic case, where one uses normalization for the static and high-frequency fields.
24-28
Study of an End-Fed Dipole Antenna Excited by a Rectangular Waveguide
Аннотация
We present the results of analysis of a dipole antenna fed via a rectangular waveguide and based on a recently proposed end-fed dipole. Both the radiation resistance and the complex input impedance of such an antenna are determined using the mirror image theory and the induced EMF method. The principles used for an optimal choice of the radius of the antenna conductors and the size of the wide wall of the waveguide are discussed. The experimental results indicate that the proposed approach is correct.
29-36
Application of the Two-Particle Correlation Function Approach to the Description of a Single-Pass Free Electron Laser Operated in SASE Mode
Аннотация
We describe the theory of a superluminescent single-pass free electron laser based on the Bogolyubov chain of equations for multiparticle distribution functions. Special choice of the variables eliminates the retardation of interaction. A small parameter (inverse number of particles per signal growth length in the accompanying reference system) for the chain truncation is found. Expansion over this parameter makes it possible to neglect three-particle correlation functions and solve only the equations containing a single-particle distribution function and two-particle correlation functions. The calculation results are in good agreement with the conclusions based on the previously developed quasilinear theory.
37-53
Processing of Antenna-Array Signals on the Basis of the Interference Model Including a Rank-Deficient Correlation Matrix
Аннотация
We propose a new method of signal processing in antenna arrays, which is called the Maximum-Likelihood Signal Classification. The proposed method is based on the model in which interference includes a component with a rank-deficient correlation matrix. Using numerical simulation, we show that the proposed method allows one to ensure variance of the estimated arrival angle of the plane wave, which is close to the Cramer–Rao lower boundary and more efficient than the best-known MUSIC method. It is also shown that the proposed technique can be efficiently used for estimating the time dependence of the useful signal.
54-64
Estimation of the Moments of Appearance and Disappearance of a Radio Signal with Unknown Amplitude and Initial Phase
Аннотация
We synthesize the quasilikelihood, maximum-likelihood, and quasioptimal algorithms for estimating the moments of appearance and disappearance of a radio signal with an arbitrary shape of the envelope function and unknown amplitude and initial phase. Asymptotic characteristics of the operation efficiency of the synthesized algorithm are found.
65-80
Study of the Stationarity of Random Time Series Using the Principle of the Information-Divergence Minimum
Аннотация
Using the theoretic-information approach and the criterion of the information-divergence minimum in the Kullback–Leibler metric, we propose a new algorithm for checking the time series for stationarity in a broad sense. We consider an example of realizing this algorithm, study its dynamic characteristics, and give recommendations on its use under conditions of small samples.
81-87