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With the advent of new technologies, the requirements for the sources of reference vibrations are becoming more stringent. They must be compact, quickly reach frequency, operate in a wide temperature range and have a small relative frequency drift in the operating temperature range. Changes in ambient temperature are the most destabilizing factor for the oscillator output frequency. Ensuring frequency stability over a wide temperature range is a pressing task. Thermal compensation allows increasing frequency stability over a wide range of operating temperatures. This is achieved by compensating for the effect of the destabilizing factor on the generator so that the frequency drift tends to zero as the temperature changes. Temperature-compensated quartz oscillators are highly stable and have a short readiness time. However, to create generators with a frequency stability of ± 0,1 ppm, imported components are required, which makes their production difficult in modern conditions. A technological chain is created at the JSC «LIT-PHONON», which allows producing a quartz resonator using only Russian components. The goal is to use these resonators in temperature-compensated oscillators with frequency stability of ± 0,1 ppm. However, the analysis showed that the resonators have problems with frequency drift over time during operation at a maximum operating temperature of + 85 ºС. Additional adjustment of generators during operation is required. It is also revealed that some Russian components are not ideally suited to the developed technological process, which may negatively affect the yield of suitable products. The measuring setup also has an error of ± 0,5 ppm, which does not allow an accurate assessment of the frequency stability of the resonators.

The article considers the possibility of developing control systems for the technical condition of radio beacons (RB) transmitting channels generators for the airport navigation and landing complex using artificial intelligence systems (AIS). The feature of using AIS to develop the technical control system is integrating a multidimensional likelihood function into the knowledge base. By means of merely measurements of signal phases generated in RB, the given function makes it possible to evaluate:– average frequencies of generated signals in RB;– deviations of average frequencies from the required values throughout the entire observation interval;– random deviations of the current frequency values from the average ones at each measurement interval;– relative frequency instabilities of each of generators.The results obtained and their variation over the time allow us to carry out:– monitoring the technical condition of RB channels generators;– diagnostics of the technical condition of RB channels generators;– forecasting the technical condition of RB channels generators and making a decision concerning the status of the controlled generators according to the CORRECT OPERATION-DETERIORATION-FAILURE criterion.

The article considers the problem of designing a synchronized aerial wireless sensor network of unmanned aerial vehicles (UAVs) with centralized control by a master unit. A 10-ns synchronization precision must be ensured for all units within the aerial network in the time intervals of at least 100 s. To achieve it, the master unit periodically generates a synchronizing signal with two coherent sine tones of different frequencies that helps the slave UAVs to adjust their clocks. High-stability oven-controlled crystal quartz oscillators (OCXO) are used as onboard clocks for the UAVs. The study aims to assess the optimal frequency separation of the coherent synchronizing tones that provides the best possible noise immunity of the measured data with a reliable ambiguity resolution of the carrier phase. The problem is solved using a computer simulation of periodic synchronization of the slave UAVs by differential phase measurements associated with the reference time scale of the master UAV in order to suppress possible random clock offsets. According to the simulation results, aside from the positioning errors of the UAVs, the systematic Doppler phase shift of the synchronizing signal in the propagation channel is the main obstacle to differential phase synchronization. Depending on the efficiency of the Doppler phase shift compensation, the optimum frequency separation of the synchronizing tones ranges from 10 to 1500 MHz with the correspondent synchronization precision achieved from 0.25 to 2.65 ns at the observation time of up to 100 s. It is shown that the effective compensation for the Doppler shift requires periodic channel estimation for at least every 10 ms. For most practical applications, however, adjusting the slave clock every 5 s using two coherent synchronizing sine tones separated by 400–500 MHz results in a satisfactory quality of synchronization.

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.

The article based on the method of statistical frequency stabilization deals with the issues of increasing frequency stability and synchronization of the forming HF signals in a transmitting device of a localizer using a multichannel variant of construction. It was demonstrated that the available digital unit of frequency and phase correction allows easy application of the proposed method. Two main features of the localizer operation affecting frequency stability and phase synchronization of HF signals are noted. The first factor is determined by deviation of the present -HF signal frequency (on the measurement interval) from the average (i) frequency value in n-channel. The second one is related to average frequency variation of each of the forming HF signals and its deviation within the (i) value from the nominal value during localizer operation. On the basis of HF signals description in channels of the transmitting device of a localizer ratios are obtained determining optimal values in terms of the method of least square method as (i) deviations of the present frequency values from the average value as well as variations of average frequency values during localizer operation. The article considers the most significant, from an applicatory point of view, case of assessment covering only deviations of the present HF signals frequency values from the average value on the measurement interval. It is shown that application of the method of statistical frequency stabilization allows the transmitting device of a localizer including N channels of HF signals formation to increase frequency stability and HF signals phase synchronization times. That enables to improve accuracy of forming integrated and difference directivity diagrams and setting heading in the runway direction as well. Apart from that, on the basis of the received values of frequency parameters estimation and relative instability of the forming HF signals a decision can be made about the condition of the controlled parameter by the criterion STANDARD-DETERIORATION-ACCIDENT.

In modern microwave electronics, it is extremely important to evaluate the possibility of efficient generation of highly stable oscillation modes and the creation of low-noise generators with a millimeter wavelength range. The purpose of the research was to determine the type of wave for the most effective modes of oscillation and to ensure the operation of various modes in the mode of mutual synchronization, which becomes possible because the real design of generators can include a number of reactive elements that form a number of resonant frequencies in the microwave range. This paper shows how it is possible to provide conditions for generation at a particular frequency and simultaneously obtain high stability of vibrations. The main research methods were: analysis and generalization of literature data and results of our own research on the peculiarities of oscillation generation in a multi-circuit system of a Gann diode generator and conditions under which high frequency stability is established; experimental studies using microwave spectrum analyzers, microwave devices. In this paper, the possible generation frequencies are calculated, the operation modes of the diode generator are studied, and their phase noise is experimentally measured. It is shown that when the generation frequency approaches the cut-off frequency of the waveguide with the help of structural elements or by changing the supply voltage, a mode of mutual synchronization of vibrations at high harmonics occurs using the H102 wave type in a very narrow range of frequency (phase) noise. A generator with a multicircuit resonant system was experimentally studied and a small amount of phase noise was obtained for both types of H101 and H102 waves. At the same time, the best parameters and noise characteristics occurred at the lowest types of vibration types. These results have an experimental novelty, which allows us to hope for the development of constructive solutions that provide the creation of highly stable low-noise generators of millimeter wavelength range with the minimum mass dimensional parameters.

The article deals with the problems of frequency stabilization of generators in distributed information-measuring systems on the basis of the static frequency stabilization method. The examples of similar systems are given. The necessity to ensure high stability of signal frequency generated by subscribers to improve the efficiency of the stated systems is noted. Two main features of applying the static frequency stabilization method are stated. The first one is determined with a delay in signal input into the device for estimating the frequency-time signal parameters in relation to the signal phase measurement interval. The second feature involves the entry delay of the formed control signal of generator frequency correction. It is shown that the mentioned features lead to divergence of the current variation of generator frequency and the value under correction, obtained considering the delay. The description of information signals enabling to specify a mathematical model of the process of assessment forming of the information signal frequency variation, taking into account the mentioned factors, is offered. It is shown that the possibility of using a statistical method to stabilize the frequency of generators in distributed informationmeasuring systems is determined not only with the values of nominal frequencies and relative instabilities of generators included into the information-measuring system, but also by the autocorrelation function of a random process describing the change of information signal frequency. In case of small time delays between the evaluation of information signal frequency and frequency stabilization, the use of the method to be considered allows to reduce the relative instability of information signal frequency. When time delays are greater than the correlation interval, the use of the statistical method does not lead to the change of relative instability of information signal frequency. Within the correlation interval, the use of the statistical method of frequency stabilization can cause depending on the autocorrelation function values both decrease and increase of the relative information signal frequency instability.

Subject and purpose. Open resonant system as the oscillating circuit of the solid-state oscillators and characteristics of the quasi-optical oscillators properly are the object of investigations. Purpose of article is review of works being fulfilled at the solid-state department over period 1979 and to the present day. The intent of the paper is to give the indication prerequisites of the creation of high-stabilized millimeter wave sources and way of this problem solution. Method and methodology. Theoretical and experimental methods of study of main parameters of open resonators with resonant and nonresonant inhomogeneities such as spectrum, field topology of open resonators are the waveguide model of resonator, decomposition method, generalized scattering matrix method, and experimental technique of the power, frequency, and spectrum measurements. Results. Results of study and development of quasi-optical solid-state oscillator are: the level of frequency noise is no more than –115…120 dB/Hz; power of generation at first harmonic is up to 130…150 mW at frequency of 40…50 GHz; at second harmonic – up to 10 mW at 60…90 GHz; generation power is no more than 3 mW at frequency of 150 GHz ; long-term frequency instability is 3×10–8 at active control temperature DТ ~ 0.1 °С. Conclusion. In the paper it is analyzed an application area of solid-state oscillators. They are local oscillators in receiving units and radiometers, refractometry, dielectro-metry, and fields where high stability and low level of frequency noise are needed. The promising lines are inquired, they are search of new physical properties for nonlinear element creating at Terahertz frequency band.

The investigation objective is to simulate the process of generator frequency stabilization as in the case of a component of the cellular system “switching centre - base station”. The aim of the work is to establish dependences between the generator parameters (a number of generators, operation frequencies, and relative instability of frequencies) and the generator frequency stability. The study is based on the application of the numerical analytic model of the generator signals, and on the construction of the plausibility function when the unbiased, asymptotically efficient and consistent estimates of each generator are specified from the maximum condition. The research suggests the following results. Under the cooperative processing of the measured values of the signal phases of the simultaneously and independently operating generators, the unbiased, asymptotically efficient and consistent estimates of the generator frequencies may be obtained. This ensures the frequency stability augmentation. The use of the numerical simulation allows estimating gain in reducing the relative instability of the frequency signals depending on such infocommunication system parameters as a number of generators and their relative instability.

The possibility of reducing the influence of low-frequency noise in the laser phase-frequency rangefinders, which leads to a shortterm instability of converting links of the device has been reviewe. This is achieved through the use of filtering the output signal of the phase-frequency system, the frequency which is proportional to the measured distance. The electronic simulation of converting processes in such system was carried out for which the output signal models in analog and discrete form were received. The results of the simulation allow to choose optimal parameters for a high pass filter according to the allowable value of the error arising from the transition processes in it. By numerical simulations assessment of the random error of the device due to the influence of broadband noise has been carried out. The simulation results are presented as a function of the random error from the signal/noise ratio for the selected filter time constant. [ABSTRACT FROM AUTHOR]