Radio physics and electronics

11-21

Authors: V. N.Skresanov, V.V.Glamazdin

A method is proposed for measuring the Q-factor of microwave resonators, which allows the study of microwave properties of materials and environments using open resonators of different types under conditions of availability of close-frequency modes in the surroundings of the given mode, the radiation losses of coupling elements and crosstalk between them. Measurement of the loaded Q-factor is based on both the representation of the frequency dependence of the resonator complex reflection or transmission coefficients by the sum of fractional-linear complex functions, describing the responses of individual modes, and approximation of a square measured frequency response by means of the variation gradient method. The eigen Q-factor calculation method is based on calculation of the resonator impedance on the measured reflectance modulus. The developed algorithms for processing measurement data are implemented in a computer program and are illustrated by the example of the processing frequency dependences of S-parameters for the open dielectric mirror resonator excited with whispering gallery modes, when the S-parameters are calculated by finite element method. Measuring quality factors by the proposed method eliminates the systematic measurement error associated with the distortion of the resonance curves, and makes it possible to perform measurements in conditions where classical methods are unsuitable.

30-37

Authors: A.P. Nickolaenko, Yu.P. Galuk, M. Hayakawa

Investigations of link between parameters of global electromagnetic (Schumann) resonance and characteristics of vertical profile of atmospheric conductivity remain an actual problem. We use a rigorous solution of the electrodynamic problem in the spherical Earth-ionosphere cavity by the full wave technique and compare the results with the knee model, as introduced in the literature. The vertical conductivity profile of the atmosphere was constructed by using parameters of this model, and this allowed us to build the rigorous electromagnetic solution, and to compute the energy spectra of the vertical and horizontal electric magnetic fields corresponding to the uniform distribution of the global thunderstorms over the planet. It is shown that the knee model, discussed in the literature, does not match the rigorous full wave solution and the subsequent computations of the power spectra of Schumann resonance.

49-54

Authors: A.E.Kogut, R.S.Dolia, S.O.Nosatiuk,He Jaochan

The spectral and energy characteristics of the shielded halfspherical resonator at the forced oscillations mode are investigated experimentally at using of the slot-line. It is shown that the use of slot-line allows maximally rarefying the spectrum of forced oscillations of the shielded resonators with an exceptional allocation of whispering gallery modes and achieving the greatest Q-factor. The experimental investigation and computer simulation show that the slot-line is a channel waveguide having the resonance properties.

62-65

Authors: A. S. Vakula

Magnetic nanoparticles are used extensively in various areas of science and technology due to ability to vary their parameters over a wide range. Magnetic properties of the nanoparticles depend strongly on technique of synthesis. The impact of various techniques of synthesis on the magnetic properties of the nanoparticle is not studied well now. Therefore, in this paper the microwave magnetic properties of the Fe3O4 nanoparticles prepared by various techniques of chemical synthesis are under research. The magnetic properties are studied by the ferromagnetic resonance technique at T = 77…300 K. It is shown that the resonant frequency increases when the diameter of nanoparticle rises. The diameter depends in turn on the technique of synthesis. Also it is shown that when the temperature increases the resonant frequency and linewidth are decreased. The results of investigation can be used to select an optimal technique of synthesis of Fe3O4 nanoparticles with specified magnetic properties.

72-78

Authors: O.V.Zemlyaniy

Application of chaotic signals in modern radar and telecommunications is an actual task that can significantly extend the functionality of these systems and improve their performance. In this paper, a method for information transmission using chaotic signal generated by nonlinear dynamical system with delayed feedback of ring type has been suggested. Modulating information sequence controls the parameter of non-linear element, so that it switches the chaotic modes and changes the spectral structure of the signal transmitted to the communication channel. A non-coherent reception was used for demodulation of the received message. The effectiveness of this method of information transmission for the covert operation of communication system in a complex interference environment has been shown.

90-95

Authors: I. P. Storozhenko

The use of variband semiconductors in uniformly doped devices with the effect of intervalley electron transfer can lead to the appearance of a static electric domain. The interest in the static domain is due to the possibility of creating a local electric field sufficient for impact ionization of zone area. Diodes with avalanche ionization in the static domain can be used as active elements of noise generators. The article analyzes the process of formation of a static domain and avalanche multiplication of current in it on the basis of the two-temperature model variband AlGaAs. It is shown that for the formation of a static domain at room temperature, it is necessary that the minimum value of the energy gap between the G-valley and the closest by energy side valley was smaller than the thermal energy of the electrons at the rate of change of the energy gap to coordinate more than 150 eV×cm–1. Accordingly, in devices based on Al0.36Ga0.64As–GaAs cathode static domain is formed, and on the basis of GaAs–Al0.36Ga0.64As anode static domain is formed. The variband semiconductor compounds in which it is possible to form a static domain were determined. Using variband compounds Al0.36Ga0.64As–GaAs with low levels of doping in the vicinity of the cathode increases the effective and integral current multipliers as compared to GaAs-diode. The findings expand the knowledge of the physical processes of charge transport in complex semiconductor structures. They can be used for technological development of new high-speed devices, such as transistors, Gunn diodes, diodes with a stationary domain, avalanche-transit diodes, frequency multipliers.