Radio physics and electronics

4-14

Authors: S. L. Berdnik, V. A. Katrich, V. I. Kiyko, M. V. Nesterenko, Yu. M. Penkin

The study of peculiarity of influence of the impedance insertions on the electrodynamic characteristics of the rectangular waveguide junctions, which are widely used in the antenna-waveguide devices, is important for practical applications. A mathe-matical model for E-plane T-junction of rectangular waveguides with a three-element vibrator-slot coupling structure was built using approximate analytical solutions of equations for induced currents by a generalized method of electro-magneto-motive forces. The distinctive feature of the model is the usage of variable surface impedance along the monopole axes and constant impedance, distributed over the end wall of the lateral semi-infinite waveguide. Multiparameter energy characteristics of the junction in the single-mode waveguides are presented including the case of meta-material coating the end wall of the lateral waveguide. The possibility of efficient use of impedance coatings as control element for power division between the output waveguide junction arms is shown.

22-30

Authors: Yu. A. Pedenko

The work is devoted to improvement of the accuracy of radar measurements of elevation angles of low-altitude targets above sea level when using the root-MUSIC, which is considered by experts as one of the means to solve this problem. Unlike previous studies, which take into account the multipath only, in this study the clutter is complicated by thermal noise of radar. This allows to evaluate the capabilities of the method and provide guidance on its application in the conditions close to reality. The study was carried out by computer simulation. It covered various sea states at which the conditions from specula to strong diffuse reflection were complied. In the simulation a wide range of signal/noise ratio was used. The main focus was the study of effects on measurement errors of a priori parameters of the method: the signal subspace dimension and the order of autocorrelation matrix of signals received by a multi-element antenna array. The recommendations of their choice, allowing to minimize the errors of elevation measurement in different conditions, have been developed. The results of the study extend the knowledge of how to improve the methods for measuring the target elevation angle above the sea.

40-47

Authors: V. V. Ovsyanikov

The actual problem of studying the basic properties and searching for methods of improving the plasma radiator array, which is similar to the array of metal or dielectric antennas, has been considered. This problem is not sufficiently covered in the well-known publications, however, the great interest of professionals to emitters based on cold plasma is due to the prospect of creating effective multi-beam scanning selective plasma reconfigurable systems or the plasma array of radiators (PAR). The article studies the main electrodynamics parameters of PAR in the microwave range, characterizing it on the one hand, as the load for the generator (receiver) of electromagnetic (EM) signal. On the other hand, PAR is tested as transmitter of EM energy from the point of view of its direction pattern (DP) and the main parameters of radiation of PAR. When scanning DP beam, impedance distortion of PAR transmitters and DP deformation are investigated. For comparison, similar studies were carried out for the same design and configuration of the pattern antenna (PA) of metal antennas. The studies have been carried out by PAR modeling and their parameters calculations on computer in software environment FEKO by integral equation method and method of moments for linear PAR from 4 emitters in the form of loop dielectric tubes filled with cold plasma under reduced pressure. When studying the self and mutual impedances of the PAR and metal PA in common mode for the distance between the transmitters 0.5l0, where l0 is the central wavelength of the test range, it has been determined that electromagnetic interference between antennas in PAR is less than in the metal antenna array, and when reducing the distance between transmitters grating with 0.5l0 – 0.25l0 the relative change in value of units of the input impedance of each radiator of PAR is twice less than for a lattice of aluminum, which allows to bring together the radiator of PAR without a substantial increase in interference between them. From comparison of DP of radiant systems of PAR and aluminum arrays while scanning, it is obvious that DP of PAR are less distorted than aluminum array. The obtained results can be used for calculations and design of plasma array of radiators.

55-60

Authors: P. P. Maksymov

Construction of powerful sources of electromagnetic oscillations of microwave range is an actual task for creating modern semiconductor devices. In this paper the creation of powerful sources of electromagnetic oscillations based on reverse-biased abrupt p–n-junctions of avalanche-generator diodes (AGD) with external signal has been theoretically grounded. Classification of modes of avalanche-generator diodes has been carried out. The choice of oscillations generation mode is determined by the parameters of AGD and input signal. It is shown that coherent, multifrequency and broadband oscillations are generated in AGD. Power and spectral descriptions of oscillations of AGD are presented. The research results are of interest for the developers of powerful diode generators with the required range, power and spectral characteristics.

71-76

Authors: Z. А. Maizelis

For detecting and establishing the nature of frequency noises in the oscillating system, it is very important to separate different types of noises. For determination of characteristics of the frequency noise it is necessary to study statistical properties not of actual coordinate and its derivative, but of complex coordinate of oscillator. Its moments do not depend on the amplitude noises that often can prevail in the system. The growing interest in noises of frequency is related to the fact that they determine the loss of coherence of vibrations in many systems, from the devices based on Josephson contacts, to the nanomechanical resonators. The knowledge of statistical characteristics of frequency noises inevitably present in the devices of information read-out in quantum computers will allow correct processing of the information in them. Here the influence of the telegraph unbalanced noise of frequency on properties of electromechanical resonator is studied. It is shown that the dependencies of the higher cumulants contain features, which allow to separate the effects related to the presence of noise of frequency. The results may be useful in the theory of nanomechanical resonators, in processing the data, obtained in the radio-technical devices and devices, based on Josephson contacts, in quantum computers, in the estimation of precision of atomic clock.

85-91

Authors: V. P. Ruban

The estimation of synchronization instability becomes actual in GPR due to the fact that this phenomenon affects the accuracy of recording and reproducing the received signal forms and, accordingly, the efficiency of use of digital signal processing algorithms. The existing method for estimation of jitter of the GPR receiver using errors of the converted signal amplitude is not universal and should be corrected for the case of converter with incomplete charging of the storage capacitor. Simulation of the stroboscopic conversion with instability of sampling interval for cases of full charging (when the evaluation method gives correct results) and incomplete charging of the storage capacitor has been done in this paper. The relationship between the forms of probabilistic distribution of jitter and errors of amplitude after stroboscopic conversion has been analyzed. The jitter values originally specified in the simulation and the ones calculated (reconstructed) by a known method also have been analyzed. According to the simulation results, the limits of applicability of this method were determined. It is shown that the direct application of the jitter evaluation method which is right for the converter with a full charging gives incorrect estimates for the one with incomplete charging of storage capacitor. Due to this, the signal amplitude recovery procedure which allows obtaining a correct estimate of the jitter of synchronization of GPR receivers operating in the mode of incomplete charge storage capacitor has been suggested.