Method for estimating time length using simultaneous phase measurements in the system of simultaneously and independently operating generators

Introduction. This paper is devoted to the development of a method for estimating the current time-frequency parameters of each of a set of simultaneously and independently operating generators in the radio electronic system. A general case is considered, in which the deviation of true values of the nominal generator parameters from the assumed values of these parameters is determined not only by random, but also by long-term frequency deviation. The work objective is to generalize the method for estimating the time-frequency parameters of signals (long-term nominal frequency and current frequency deviation from the nominal value) based on the simultaneous measurement of the phases of signals generated in the system of independently functioning generators. The research task is to consider a system of simultaneously and independently operating generators. Each of them generates harmonic signals, whose time-frequency parameters, such as the average frequency, are constant during a certain interval of observation. But herewith, these time-frequency parameters are known with insufficient accuracy due to the influence of external factors (changes in temperature, pressure, supply voltage, etc.). It is required to obtain estimates of the time-frequency parameters of signals (the duration of the measuring interval, values of the long-term frequency and the standard deviation) from the results of measurements of the phases of signals formed by the generators at measuring intervals belonging to the observation interval, within which the average frequency remains constant.Materials and Methods. A system of simultaneously and independently functioning generators is considered. The long- term value of signal frequency for each of the generators over the observation interval remains constant, but it is known with some margin of error. During the observation interval, several measurements of the signal phase of each of the generators are performed. At the same time, the current values of the signal frequency and the duration of the measuring interval have random deviations from the long-term values, and follow the normal distribution law with zero mathematical expectation and a known variance. The estimation of time-frequency parameters based on the results of measuring the signal phases is carried out using a multidimensional likelihood function. The maximum is found on the base of solving the redefined system of linear algebraic equations.Results. A new mathematical model and a numerical-analytical method for determining the time-frequency parameters of signals are developed. They take into account both the long-term constant frequency deviation and short-term random deviations.Discussion and Conclusions. The results obtained can be used under the development and creation of data-measuring and information-telecommunication systems, including geographically distributed systems. The resulting estimates of the time-frequency parameters enable to increase the signal frequency stability and, accordingly, to improve the accuracy of measurements and the quality of information transfer.

COMPARISON OF THE PARAMETERS OF SIGNALS WITH EXTERNAL ILLUMINATION FOR SUPERVISION OF THE AREA FOR THE PROTECTION OF IMPORTANT STATE OBJECTS

In modern conditions, it becomes necessary to create security systems, surveillance systems, anti-terrorist systems that carry out covert detection and surveillance of small-sized ground objects, including biological ones. Traditionally used single-position radars are ineffective in conditions of a large number of reflections that interfere with and low speed of movement of detected objects (people). The use of several such radars is impractical due to their rather high complexity and cost. In addition, it is impossible to ensure the secrecy of such systems. The construction of radar surveillance systems in the form of semi-active bistatic, including educational, radar systems is promising for the described conditions. One of the important issues in the construction of semi-active bistatic systems is the substantiation of the parameters of external illumination signals and the assessment of the attainable characteristics of such systems when using them. The analysis and definition of the requirements for the characteristics of the illumination signals is carried out. In addition, consider the features of using signals from modern emitting systems in semi-active radars. The basic parameters of the signals are given – the bandwidth, the pulse duration (spectrum width), the power at the transmitter output, the frequency range in which the system operates. The advantages and disadvantages of semi-active radar stations (SA RS), which use such signals, are described. Variants of semi-active bistatic systems with external illumination are determined. The widespread use of modern digital language and telecommunication systems provides the SA RS with effective illumination signals with good correlation properties, which makes it possible to obtain the necessary technical characteristics in a variety of application conditions

Estimation of electromagnetic compatibility of a narrow-band radio channel under the influence of unintended interference of the radar complicated pulse signals

The relevance of estimation of the electromagnetic compatibility (EMC) of narrow-band radio communication channels under the influence of unintended interference (UI) from radars with complex signals is due to the widespread use of both the first and second ones. At the same time, its equipment is often installed at the same carriers, which further complicates the task of providing EMC. The specificity of this situation is that narrow-band radio channels occupy a frequency band measured in few kilohertz, and the width of the spectrum of complicated signals used by radars is several and tens of megahertz. Under these conditions, during the preliminary estimation of the EMC, it is advisable to use the method of mathematical modeling and approximate a narrow-band radio receiving device (RRD) exposed to broadband UI with an equivalent circuit characterized with a given degree of accuracy by the parameters of this RRD. In this case, we used a chain approximation of the 4th order. This chain is represented by a system of differential equations that is solved in MATLAB. As a result of calculations, the dependence of the coefficient of suppression of unintended interference on the parameters of signals, interference and radio receivers was found. It was found that in the example under consideration, the suppression of unintended interference is at least 37 dB.

Measuring the acoustic signals parameters of the defect simulator of power transformers

Background: The article describes a device for simulating defects for use with acoustic control systems for high-voltage transformers. Aim: experimental research of a mobile device for imitation of power transformer defects; determine the parameters of impulses simulating various insulation defects Methods: development of technical means for imitation of insulation defects; experimental research; determination of parameters of signals simulating defects. Results: a block diagram of a device for imitating defects is shown; experimental studies of the device for imitating defects were carried out; the power of pulses simulating various defects in the insulation of high-voltage transformers was calculated. Conclusion: The proposed device generates high-voltage pulses that simulate various defects in the insulation of high-voltage transformers. The parameters of acoustic signals are given.

Development of methods for modeling digital signals when designing printed units

In the production of printed circuit assemblies, one of the important stages is to carry out various forms of product control. Control of the electrical parameters of signals for various modes of operation of the device is one of the key tasks, since possible deviations can lead to malfunctions in the operation of the product or inconsistency of its output characteristics with the limitations set in the technical specifications. Electrical control is carried out using test samples of products and in a number of cases the methods used are quite costly both in time and in terms of the cost of the equipment used. This article discusses the issues of building models of key parameters of digital signals. The relevance of this study is due to the need to analyze the behavior of electrical signals in preparation for the serial production of printed circuit boards, which will ultimately allow obtaining the required information about the signal and assessing its quality. The proposed model of a digital signal is universal, applicable for different values of time constants, and allows one to evaluate characteristics based on directly measured parameters of a digital signal or on the basis of a given sample. The model allows you to take into account a wide range of voltages, noise levels and parasitic parameters of circuits.

DEVELOPMENT OF AN ALGORITHM FOR DIAGNOSING DENTAL DEFECTS IN REDUCERS OF SELF-PROPELLED AGRICULTURAL MACHINES

Intensive use of agricultural production technologies has recognized the intensive characteristics of agricultural producers, which allowed to present the need for frequent diagnostics, maintenance and repair. This transition is due to objective trends in the development of agricultural machinery. The solution to this problem involves the development and creation of effective tools for monitoring and diagnosing the state of the transmission elements of agricultural machinery; assessment of the value of the residual life of individual elements of the system and the study of energy conversion processes in these elements; construction of mathematical models on the basis of which it is possible to predict the occurrence of dangerous damage depending on the operating conditions of the equipment. Diagnostic means must ensure the assessment of the condition of the working surfaces of the interacting transmission elements, control of wear of their surfaces and assessment of the performance of the unit as a whole or the kinematic pair without their disassembly during operation. The time of collection of diagnostic information and allocation of informative signs and parameters of signals should be minimized. Control methods should be as simple as possible, and the means that implement them - compact, with built-in algorithms for information processing and decision-making. The most informative parameter that carries the maximum information about the state of the unit of a working machine or unit is mechanical oscillations (vibrations) - elastic waves propagating in continuous media. Measurement of vibroacoustic characteristics on bearing supports of mechanisms allows to recognize such defects and damages as imbalance and skew of shafts; damage to plain and rolling bearings; damage to gears in gears; damage to couplings; damage to electrical machines. With the systematic use of modern diagnostic methods it is possible to avoid serious damage to the transmission elements and reduce operating costs for maintenance of agricultural machinery due to the fact that the repair is carried out only when the measurement results indicate its need.