Radiothermal radiation method for aqueous solutions

For the first time, an ultra-high-sensitivity method for measuring radio-thermal radiation was developed and used in practice in order to establish the difference in the physical properties of aqueous solutions of substances in the millimeter region of the spectrum. The method is used to study the dynamics of the dielectric properties of aqueous solutions depending on the composition of the base substance and its concentration. The dynamics of dielectric properties establishes a one-to-one correspondence between the number and concentration of ions of the dissolved basic substance contained in water and the number of water molecules involved in cooperative interaction, which gives a consistent microscopic picture of ion-water cooperative interactions in the studied aqueous solutions of K2SO4 and Cs2SO4. The density of water molecules perturbed by the ions of the base substance contained in the hydration shell at normal concentrations is proportional to the number of ions, while the transition to weaker solutions leads to the creation of multilayer hydration shells. This means that the number of perturbed water molecules, depending on the number of ions, increases according to a law different from linear. In accordance with the experimental data, the values of the absorption coefficients of aqueous solutions were determined in a wide range of concentrations for alkali metal sulfates. It is noted that alkali metal sulfates have physical properties that generalize the dynamics of dielectric constants depending on the concentration of the base substance. A monotonic increase in the values of the absorption coefficients of solutions with a decrease in the concentration of basic substances in the region of high dilutions was established with individual dynamics for each basic substance, reflecting the total hydration changes in salt solutions. Research has shown that the proposed method for measuring radio-thermal radiation fixes a significant difference in the values of the dielectric constants of aqueous solutions at high dilutions from their values for water.

Multi-channel interference source detector

Modern radars, along with the detection and measurement of target coordinates against the background of interference, must solve the problem of detecting radio emission sources and measuring their coordinates. Detection of interference, as well as targets, in the radar is provided in the main (total) channel based on the analysis of the rangefinder-Doppler portrait of the received signal. The main disadvantage of such a detector is that the interference coming along the side lobes of the sum antenna and falling into the dip of the antenna radiation pattern may not be detected. Therefore, the problem arises of developing and analyzing algorithms for detecting interference in a radar with several receiving channels. The article discusses the logical, energy, correlation and eigenvalues of the cross-correlation matrix of the received signals interference detectors for two receiving channels. Their characteristics are given. It is shown that two-channel interference detectors based on the analysis of the eigenvalues of the cross-correlation matrix have the highest efficiency. Energy and logical algorithms are quite a bit inferior to them. The developed algorithms make it possible to effectively detect radio emission sources even when they are in the dip of one of the antenna patterns.

Observation of quadrocopters by radar with long-term coherent signal accumulation

The article discusses the experimentally obtained characteristics of radar signals reflected from small-sized aerial targets such as a quadrocopter, with their long-term coherent accumulation. A brief description of the structural diagram of the experimental radar and its characteristics is given. The radar operates in the ten-centimeter wavelength range and emits a coherent-pulse signal. The duration of the emitted chirp pulse is 1 μs with a compression ratio of 15. Algorithms for primary processing of signals in a computer are given, including compression of chirp signals and spectral analysis of the received implementation, which is equivalent to its coherent accumulation. The parameters of the generated radar image are determined. The characteristics of the targets used - the small-sized quadcopters Mavic and Phoenix – are given. As a result of the experiments, it was shown that the tested small-sized air targets in the ten-centimeter wavelength range of the probing signal have their own coherence time sufficient for the coherent accumulation of the signal reflected from them for a time of at least 0.2 seconds. The Mavic does not produce reflections from its rotating rotors. The main rotor of the Phoenix quadcopter creates spectral components in the image, concentrated along the speed axis in the form of maxima symmetrically located relative to the central mark of the target. The presence of this feature of the signal allows you to identify the type of target, highlight the target against the background of birds, and detect a stationary, hovering target. It is shown that the features of signals reflected from the ground, with long-term coherent accumulation, allow providing the minimum speed of the detected target, measured in fractions of a meter per second.

Synthesis of an algorithm for increasing the detection range of signals from radio-electronic means by means of radio control based on the estimated-correlation-compensation processing of signals with an unknown shape and additive noise in the receiving channel

In modern conditions of rapid development of telecommunication technologies radio engineering means of different function are used everywhere in all spheres of ability to live of the person. Thus organizational-technical systems of civil appointment and power departments use the wide nomenclature of radio-electronic means of various classes with a wide spectrum of parameters, kinds of radiations and operating modes. In turn, it causes formation of difficult electromagnetic conditions in administrative-industrial regions and their near environment. The primary goal of services of radio control in these conditions is control over correctness of use by organizational-technical systems of the allocated resource of a radiofrequency spectrum and the parameters radiating of radio-electronic means. One of the main difficulties with which means of radio control in the course of the analysis of electromagnetic conditions in the set territorial area face a considerable quantity of radiating radio-electronic means with various parameters in a wide range of the relation a signal/noise, and also presence of stirring influence of any hindrances is. These factors make rigid demands to indicators of quality of functioning of panoramic detectors-direction finders which make a basis of mobile and stationary means of radio control. One of the basic indicators of quality of panoramic detectors-direction finders of means of radio control is range of detection of the radio-electronic means, defined by the set level of sensitivity and demanded values of probabilities of detection and a false alarm. Authors in article result results of working out of algorithm of increase of range of detection of signals by means of radio control on the basis of an estimated-correlation-compensatory way of measurement and indemnification of average capacity of additive hindrances in the reception channel. By results of the researches spent in article it is shown that: the increase in average capacity of cumulative external inadvertent and deliberate hindrances for the set typical initial data leads in VHF a range to reduction of range of detection of radio-electronic means not less, than in 1,4 times from the demanded; at demanded value of probability of detection, for example, and probabilities of a false alarm, at relative level of external set of a hindrance the panoramic detectors-direction finder of means of radio control with the realised procedure of measurement and indemnification of average value of capacity (dispersion) of inadvertent, deliberate hindrances and internal noise allows to lower the requirement to the threshold relation a signal/(noise) (on pressure) more, than in 1,3 times that will allow to approach value of range of detection to a reference value.

Space-time processing for «range – azimuth – elevation» measurements in non-cooperative systems of radars with phased array antennas

The methods of measuring the three coordinates of an aircraft in the takeoff and landing mode on the runway of airfields based on the use of non - cooperative two-and three-position systems of radars with phased array antennas are considered. For these variants, general analytical expressions are obtained for the complex generalized correlation integral of space – time processing in the function of spatial coordinates, taking into account the individual directional pattern of phased array antennas. On the basis of two – dimensional profiles of the correlation integral modules «range – elevation» and «azimuth – elevation», examples of comparing particular variants of two-position and three-position systems of radars with their location on one straight line parallel runway are given. In conditions of large signal-to-noise ratios, power-law nonlinear transformations of the correlation integral correlation integral module are applied to reduce the level of side lobes in the two – dimensional sections «range – elevation» and «azimuth – elevation». The following results are obtained using examples. Two-dimensional diagrams of the correlation integral module «range – elevation» do not depend on the azimuth of the aircraft in the range of azimuth values β=0…10 ̊ and correctly display the angle of elevation and the range of the aircraft when 2…3 radars of a non-cooperative system are located on the straight line parallel runway. The two-dimensional diagrams of the correlation integral module «azimuth – elevation angle» have an interference structure, and the number and level of their side lobes increase with increasing azimuth of the aircraft. With azimuth β≥10 ̊, this can lead to ambiguity in the measurement of the azimuth and uncertainty in the elevation angle . One of the measures to reduce the side level of the diagrams of the correlation integral module can be the use of a power-law transformation of normalized diagrams exponentiation of degree 3...4. An increase in the number of radars from two to three when they are located on one straight line parallel to the runway led to a decrease in the side lobes level of the «range – elevation angle» and «azimuth – elevation angle» diagrams. In this case, it may be advisable to solve the problem of optimal choice of the position of the intermediate radar on the same straight line. Calculations were also carried out for an additional example of the location of the intermediate radar of a 3-position system with its removal from the base line. At the same time, there was an increase of the side lobes level in the «azimuth – elevation angle» sections, which in the future may require additional research in terms of optimizing the placement of the radars in horizontal plane for such a radar systems.

Wideband microstrip dual polarization radiator for X-band APAA

In this paper the model and the construction of a wideband microstrip X-band radiator of active phased antenna arrays have been presented. The basic demands to the radiator have been formulated. The results of computer electromagnetic simulation of the radiator in free space and in the infinite array have been given, as well as the results of radiator experimental testing in the waveguide simulator. The characteristics of a proposed radiator such as VSWR, decoupling coefficient and losses have been simulated and estimated experimentally on the test sample. Experiment has shown good agreement with numerical simulation results. Particularly, 20% bandwidth with VSWR no greater than 2 has been achieved. Sample testing in a waveguide simulator gives 0,5 dB loss (active and return loss in radiator without loss in simulator itself). Scan angle at 3 dB gain loss, as it follows from numerical simulation results, should be no less than ±40° or ±45° in the main planes. So, proposed microstrip radiator may be used for X-band active phased arrays, which should work in 20% bandwidth with steerable polarization.

Approximation and the point of flicker-noise formation

The article refers to the field of research of noise fluctuations or flicker noise in electronic amplifiers and is devoted to the exact definition of the magnitude and shape of the spectral density of flicker-noise. The 1/f approximation of flicker noise is analyzed and the problem of its non-constructiveness in analyzing the noise characteristics of electronic amplifiers is shown. To eliminate this problem, the mechanism of physical formation of the envelope, a form of spectral density flicker-noise is defined. The physics of flicker-noise is detailed by accurate definition of the place of its formation. An accurate definition of the maximum difference of the amplifier flickernoise on the flat section of noise characteristics is given, using an explanation of the physics of flicker noise. The mechanism and conditions of the exponential increase of flicker noise and its subsequent exponential desire for maximum magnitude are explained. A simple physical approximation is given to determine the processes of forming the envelope form of the spectral density of flickernoise. The physical understanding of the formation of spectral density of flicker-noise tension in the internal structure of the transistor with the participation of external circuits of the amplifier electrical circuit is detailed. The results of the study will help developers to solve many problems of building electronic devices and optimizing their characteristics at a qualitatively new level.

Microwave filters on cavity resonators

Waveguide and cavity microwave filters continue to be the most important components of high-power radio electronic systems. Cavity microwave filters are of great interest as a separate group of devices of this type. The fields of application of such filters are constantly expanding, and the variety of their design is quite large. In addition, the requirements for their electromagnetic characteristics and reliability are currently increasing. In this regard, it becomes necessary to analyze the already created designs of these devices and study the main trends of their improvement. The objective of the present study is to review the known technical solutions of bandpass filters, made on cavity resonators of the microwave range. An overview of the designs of devices for filtering electromagnetic waves on cavity resonators with coaxial and waveguide coupling elements of various frequency ranges is carried out. It is proposed to use the configuration of basic resonators as the main criterion for the classification of these devices. In accordance with this criterion, five groups of filters are considered: on rectangular, cylindrical, spherical, coaxial resonators, as well as on resonators of complex shape. The review makes it possible to analyze the features of the implementation of different technical solutions for bandpass microwave filters of medium and high power levels and to identify the main trends in the development of this area of research.

Algorithms for detecting broadband signals with a constant level of false alarms

The use of broadband souding signals in radars, which has become real in recent years, leads to a significant reduction in the size of resolution elements in range and, accordingly, in the size of the window in which the training sample is formed, which is used to adapt the detection threshold in signal detection algorithms with a constant level of false alarms. In existing radars, such a window would lead to huge losses. The purpose of the work was to study the most rational options for constructing detectors with a constant level of false alarms in radars with broadband sounding signals. The problem was solved for the Rayleigh distribution of the envelope of the noise and a number of non-Rayleigh laws — Weibull and the lognormal, the appearance of which is associated with a decrease in the number of reflecting elements in the resolution volume. For Rayleigh interference, an algorithm is proposed with a multi-channel in range incoherent signal amplitude storage and normalization to the larger of the two estimates of the interference power in the range segments. The detection threshold in it adapts not only to the interference power, but also to the magnitude of the «power jump» in range, which allows reducing the number of false alarms during sudden changes in the interference power – the increase in the probability of false alarms did not exceed one order of magnitude. In this algorithm, there is a certain increase in losses associated with incoherent accumulation of signals reflected from target elements, and losses can be reduced by certain increasing the size of the distance segments that make up the window. Algorithms for detecting broadband signals against interference with non-Rayleigh laws of distribution of the envelope – Weibull and lognormal, based on the addition of the algorithm for detecting signals by non-linear transformation of sample counts into counts with a Rayleigh distribution, are studied. The structure of the detection algorithm remains unchanged in practice. The options for detectors of narrowband and broadband signals are considered. It was found that, in contrast to algorithms designed for the Rayleigh distribution, these algorithms provide a stable level of false alarms regardless of the values of the parameters of non-Rayleigh interference. To reduce losses due to interference with the distribution of amplitudes according to the Rayleigh law, detectors consisting of two channels are used, in which one of the channels is tuned for interference with the Rayleigh distribution, and the other for lognormal or Weibull interference. Channels are switched according to special distribution type recognition algorithms. In such detectors, however, there is a certain increase in the probability of false alarms in a rather narrow range of non-Rayleigh interference parameters, where their distribution approaches the Rayleigh distribution. It is shown that when using broadband signals, there is a noticeable decrease in detection losses in non-Rayleigh noise due to lower detection thresholds for in range signal amplitudes incoherent storage.

Calculation trajectories of stealthy movement of aircraft to a specified point in detection zone of onboard Doppler radar

An onboard radar operating in the impulse–Doppler mode has the characteristic features of the detection zone. The feature lies in the fact that at every point of the detection zone an aircraft has a sector of directions such as the onboard Doppler radar will not detect it as long as it moves in these directions. This sector is called the sector of invisible motion directions of the aircraft. Because of these features, there are such trajectories that aircraft flying along them are not detected by an onboard Doppler radar, such as an AWACS radar. The article proposes a method for planning stealthy trajectories between two given points in the Doppler radar coverage area. Trajectories are selected from a parametric family of elliptical stealthy trajectories, which are ellipses in the AWACS-associated moving coordinate system. An equation is found for the characteristic parameter of the ellipse, the solution of which allows us to uniquely identify the stealthy trajectory between two given points. The conditions for the existence of stealthy trajectories passing through specified points are investigated.