TAKING INTO ACCOUNT THE PHASE INSTABILITY OF GENERATORS CAUSED BY THE INFLUENCE OF IONIZING RADIATION OF SPACE ON THE PARAMETERS OF CARRIER FREQUENCY SYNCHRONIZATION SYSTEMS

The article investigates the possibilities of closed and combined synchronization systems for operation in the conditions of phase instability of generators caused by the influence of ionizing radiation of outer space. The inconsistency of the closed-type synchronization system with respect to minimizing the variance of phase errors and increasing the dynamics during carrier frequency tracking is shown. For the combined synchronization system, the article clarifies the process of open communication synthesis and proposes analytical dependences that allow the technique of open communication synthesis to be specified taking into account the phase instability of generators caused by the ionizing radiation of space.


Introduction
Phase synchronization systems are widely implemented in various radio engineering devices of communication, radar and control technology, as well as in devices of precise magnetic recording. In particular, in phase-coherent telecommunications and control systems, they are used to restore carrier and clock frequencies and for coherent demodulation of analog and digital signals with angular modulation [17].
The operation of synchronization systems is characterized by the influence of a number of disturbances and noise on their operation. Namely, additive fluctuation noise, perturbation of useful angular modulation (in the case of carrier frequency filtering), phase and frequency jumps and others. In space communication lines, for example, the main external perturbations are additive Gaussian noise and Doppler frequency shifts.

Formulation of the problem
Along with the external influence on the quality of the phase synchronization, the system can have internal disturbances, the main of which in phase-coherent systems are the instability of the adjustable generator [6].
In turn, one of the types of generator noise can be noise caused by the influence of one of the types of external noise, namely noise caused by the influence of ionizing space radiation (ISR) on the element base of the devices and components of communication systems [12].
The main factors of outer space that have a radiative effect on the materials and electronic equipment of space communications are [3]:  fluxes of electrons and protons of the radiation belts of the Earth;  streams of protons, solar cosmic rays and galactic heavy charged particles. The effects of radiation exposure are:  accumulation of ionization effects and structural damage in materials;  general failures and failures of elementary electronic devices when exposed to protons and other ionizing particles of cosmic radiation. The requirements for general stability, strength and stability of the equipment of space communication systems are determined by the integral effects in the materials of the elements under the influence of the ISR.
Short-term failures and reversible failures can be observed in the equipment due to the manifestation of ionization effects in semiconductor devices under the influence of ionizing radiation in outer space. In this case, the differential characteristics of the radiation, and the energy release density in sensitive volumes of semiconductors, are decisive.
In general, the effect of ISR on the generators of the synchronization system is manifested in the form of changes both in the conditions of the course of internal processes on which the principle of operation of these devices is based, and changes in the internal structure of the material from which they are made, which also affects the course of internal processes in them. Thus, under the influence of ionizing radiation in the generators, there is a phenomenon called the radiation effecta change in technical characteristics under the influence of radioactive radiation.
Radiation effects lead to reversible (stationary) and irreversible (quasistable) changes in the technical characteristics of devices [5,12].
One of the external manifestations of radiation effects in the semiconductor element base of the generator with the composition of the synchronization system is an increase in its internal noise [5].
Spacecraft synchronization systems operating under the influence of ionizing radiation of outer space must be characterized by low phase error dispersion and high speed. It is obvious that for efficient operation of the radio device as a whole, it is necessary to directly ensure high accuracy of the phase synchronization system in steady and transient modes under the influence of both external and internal perturbations [17].
The issue of determining the directions of development, analysis and improvement of known closed-type synchronization systems (CTSS) and the synthesis of new combined synchronization schemes (CSS), characterized by high noise p-ISSN 2083-0157, e-ISSN 2391-6761 IAPGOŚ 4/2020 39 immunity, accuracy and speed when working under the influence of both external and internal disturbances is an urgent and timely scientific task.

Analysis of recent research and publications
The issues of analysis of the known and the development of new schemes of phase synchronization systems, taking into account different sources of perturbations, were considered in a number of scientific works.
In [1], an algorithm for estimating phase noise based on the application of calculated coefficients of discrete discrete-cosine transformation is presented and a number of implementations of the proposed algorithm are proposed. The algorithm takes into account both the displacement of the carrier particle and phase noise, but the proposed algorithm does not take into account the assessment of the influence of internal factors, namely the instability of the generator under the influence of ISR, which adjusts to the efficiency of the synchronization system.
In [7], the results of a study of CSS with open communication under the influence of external perturbations are presented. It is noted that in contrast to simple CSS, a promising combined automatic control system in which the synthesis of open communication is offered under the condition of increasing the order of astatism has its own features due to specific input nodes of closed and open control channels. In this paper, there is no assessment of the capabilities of such a CSS to improve efficiency, taking into account the instability of the generators in the communication channel.
In [3,10,16], the optimization of the parameters of the filter and the system as a whole for the class of CSS is investigated. The obtained results showed that the CSS, due to their inherent contradictions, do not allow in some cases to ensure the required quality of work. This is especially noticeable when you want to improve the quality of the system on two or more conflicting indicators. The influence of generator instability under the influence of ISR in these works was not evaluated.
Great opportunities for improving the quality of synchronization systems exist in the class of CSS, which can combine the principles of regulation of deviation and perturbation, which were defined as promising areas for improving synchronization systems in [15,17]. In [10], the importance of assessing the impact of generator instability was determined, but in it and in [1], there is no assessment of the impact of generator instability.
In such works on CSS as [4,9], there are analyses of CSS dynamics in simple open communication consisting of the frequency discriminator (FD) and various filters (or without them), without consideration of noise both from external and from internal sources.
In [14], it was noted that the effect of generator instability can be significant. Taking it into account and minimizing it can be one of the ways to increase the efficiency of the phase synchronization system. The assessment of the impact of this instability is not described in this paper.

Purpose and objectives of this study
The problem of taking into account the impact of instability of generators in the communication channel caused by ISR on the efficiency of the CTSS and CSS has not been solved at present and is an urgent scientific problem, the solution of which is devoted to this article.
In the general case, the phase modulation of the signal contains four components [18]: where: () dt -Doppler shift at the input; () Mtuseful angular modulation; () t   generator instability. As noted earlier, the increase in the internal noise of the generator of the synchronization system under the influence of ISR causes a change in its operation in the direction of increasing the instability of the work [12].
Coherent reception requires accurate knowledge of the current phase of the carrier oscillation. When using the synchronization system as a phase filter, the input signal is, in accordance with expression (1) the sum The variance of the phase error is caused by the instability of its operation under the influence of ISR, which consists of four components [2]: The transfer function 3 () WS will be: where: ( ) 1 ( ) The transfer function for the error of the CTSS is defined by expression (5) [3,10]:   (5) hence, the transfer function 3 () WS will be: The block diagram of the linear model of KSS with an additional link, accepted for research, is shown in Fig. 1.

W S W S W S W S W S W S W S 
According to the transfer function for error CSS from expression (5), we find [7,8]: If you want the condition to be met: then the transfer functions of the CSS by error and the output signal, respectively, will be: As is known [6,13], the energy spectrum of instabilities of generators can be represented as: From this expression, it is seen that the change of the noise band in different ways affects the value of the variance of the phase error, which is caused by the instability of the generators and additive noise.
If we take the derivative by W L3 and equate it to zero, we find , the analysis of which shows that the minimum phase error dispersion is obtained by including an ideal filter (IF) in a closed loop instead of a proportional-integrating filter (PIF), which as was shown in [1], degrades the dynamics of the CTSS.
At P c /P = 610 4 , N T = 0, N f = 0.08 the following values will be optimal in terms of min The inclusion of an IF in the CTSS instead of a UIF slightly expands the noise band of the system [5].
The same increase in noise band can be obtained with a closed-loop PIF by appropriate selection of the parameters of the open channel.
Define the type and parameters of the open link, which obtains a CSS with the same band as a CTSS with an IF, but with a closed-loop PIF, the parameters of which can be selected from the condition of ensuring the required quality of system dynamics.
In other words, we will synthesize an open connection from the condition: which will optimize the system to a minimum dispersion of the phase error without deterioration of the dynamics.
In the following, we will consider the systems of synchronization with the PIF in a closed loop with a transfer function of the form [8,13]: If, in formulas (9), (10), to substitute expressions for transfer functions of links of the system of Fig. 1 of (15), (16) and (17), for n = 1, we obtain: The bilateral noise band of a CSS with PIF in a closed loop will be [11,20].
From condition (14) where: If we solve equation (23), we find the value of parameter K4 at which the optimal transfer function CSS from the condition min 2   is provided at the required quality of the system dynamics.
will decrease, deviating from the optimal value. Therefore, the open connection must be chosen to compensate for this deviation.
Explaining expression (21), we obtain the expression for increment W L  , as follows: From this expression, it is seen that at any arbitrarily small value of parameter The Doppler shift at the input of the system is determined by a function of polynomial type [18]: If we take, for example, in the calculation of the Doppler shift (25) r =0, we will receive   It should be noted that further promising research in the direction of solving the problem posed in this article is the solution of the problem of assessing the carrier frequency of the synchronization scheme considered in the work under conditions of exposure to ionizing radiation. In turn, the solution of scientific problems on the estimation of the carrier frequency of useful signals involves the choice of the estimation parameter and the method of their determination. As such a method of operation for signals that are transmitted in burst mode, it is proposed to use the maximum likelihood rule using a sliding fast Fourier [20]. In this case, the reference signal synchronization system itself can be improved by the open-loop synthesis method, which is described in sufficient detail in [20]. IAPGOŚ 4/2020 p-ISSN 2083-0157, e-ISSN 2391-6761 3. Conclusions 1. The paper considers the influence of the phase instability of synchronization system generators caused by the influence of ionizing radiation of outer space on minimizing the phase error dispersion in CTSS and CSS. 2. It is shown that for CTCC, minimization of the phase error variance by reducing the parameters of the transfer functions of the components of the system in the case of phase instability of the generators will worsen the quality of the transient process.