The scientific and practical significance of the synthesis of demodulators in solving the problem of monitoring unknown radio emissions has been substantiated. Features of the photoelastic effect are discussed in the context of constructing an amplitude demodulator. A mathematical model of the signal generation process at the output of the demodulator has been developed. It is shown that the output signal of this model is a copy of the information contained in the radio signal at the input of demodulator. In this case, the amplitude demodulator also performs the function of a low-pass filter with a characteristic cutoff frequency. A method for calculating the demodulator cutoff frequency based on the transient response is proposed. A breadboard of acousto-optic amplitude demodulator based on Bragg’s cell with the central frequency of 80 MHz has been created. A number of experimental studies were conducted to verify the established concepts. The demodulation processes of signals with amplitude and pulse modulation were considered. It has been proved by experiment that the acousto-optic amplitude demodulator reproduces information with accuracy sufficient for practice. An example of determining the cutoff frequency of acousto-optic amplitude demodulator by employing the shape of the output pulse is presented.

The article is a passive radar system of a warship. The aim of the work is to obtain the impulse and frequency characteristics for the operation and technical parameters of the delay line acousto-optic receiver new passive radar system of the warship. In this context, mathematical models of the main characteristics of the acousto-optic delay line were developed. Based on the synchronous compensation of the pulse obstacles applied to the acousto-optic receiver of the passive radar system on military ships, the full compensation of the obstacles for the effective reception signals from the acousto-optic receiver was determined. As a result, full compensation obstacles during the effective reception signals of the acousto-optic receiver passive radar system warship was determined based on the compensation impulse obstacle. Copyright (C) 2024 The Authors.

Обґрунтовано науково-практичну значущість синтезу демодуляторів у вирішенні задачі моніторингу невідомих радіовипромінювань. Особливості фотопружного ефекту обговорюються у контексті побудови амплітудного демодулятора. Побудовано математичну модель процесу формування сигналу на виході демодулятора. Аналіз цієї моделі показав, що вихідний сигнал є копією інформації, що міститься у радіосигналі на вході демодулятора. При цьому амплітудний демодулятор виконує функцію фільтра нижніх частот, який характеризується частотою зрізу. Запропоновано метод розрахунку частоти зрізу демодулятора на основі перехідної характеристики. Створено лабораторний зразок акустооптичного амплітудного демодулятора на основі комірки Брегга з центральною частотою 80 МГц. Для перевірки встановлених положень проведено низку експериментальних досліджень. Розглянуто процеси демодуляції сигналів з амплітудною та імпульсною модуляцією. Експериментально доведено, що акустооптичний амплітудний демодулятор відтворює інформацію з достатньою для практики точністю. Наведено приклад визначення частоти зрізу акустооптичного амплітудного демодулятора за формою вихідного імпульсу.

The results of the simulation based on a software algorithm designed to quantify the input matching at the input of a multichannel frequency-scanning antenna array power divider are presented. It was found that when performing wide-angle scanning in a relative frequency band of more than a few percent, the disadvantage of the known method for eliminating the normal effect is a sharp deterioration in matching in the lower and upper frequencies of the operating range. A new method is proposed based on an automated iterative process of optimizing the divider geometry, which makes it possible to obtain an acceptable match over the entire operating frequency band. The feasibility of switching from a serial power divider construction scheme to a series-parallel scheme is analyzed for wide-angle scanning in a relative frequency band of about 5%.

The paper considers the schematic diagram and operation algorithm of acoustooptic processor (AOP), the main assemblies of which are acoustooptic modulator (AOM), laser and photodetector (PD). Using the mathematical simulation, it has been shown that the signal at the AOP output contains information about the characteristics of AOM, laser and PD. The possibility of investigating the characteristics of one of the above assemblies with the known parameters of the other two by using the AOP response on determinate input action in the form of rectangular pulse has been established. A brief review of the known methods for measuring the parameters of PD and laser is presented including certain limitations of their applications. The theoretical substantiation of the possible use of AOP peculiarities for measuring the PD inertia parameters is presented. A formula for the calculation of the AOP output response to rectangular input action is proposed that makes it possible to estimate separately the time of optical beam crossing by the elastic wave packet and PD inertia. In addition, it has been proved that the configuration of cross-section of laser beam and the distribution law of power flux density in this beam could be determined on the basis of AOP peculiarities. To this end, a pulse of short duration is fed to the AOP input. Results of theoretical investigations were validated by numerical calculations and confirmed by experimental measurements.

The object of research is a mathematical model of the photoelastic interaction in an acousto-optic delay line (AODL). Two possible cases are discussed as applied to the ratio of the input pulse duration to the time of crossing the optical beam by an elastic wave packet. It is shown that in both cases the voltage at the output of the device is found as the sum of three components, which are formed by different mechanisms. If the duration of the input pulse is longer than the time of crossing the optical beam by an elastic wave packet, then the first component is determined by the process of entry of the leading edge of the elastic wave packet into the optical beam, the second – by the process of complete interaction of the optical beam with the elastic wave packet, and the third – by the process of exit of the trailing edge of the elastic wave packet from the optical beam. In the second case, i. e. when the duration of the input pulse is less than the time of crossing the optical beam by an elastic wave packet, the first term is determined by the process of entry of the elastic wave packet into the optical beam, the second – by the process of advancing the elastic wave packet in the aperture of the optical beam, and the third – by the process of exit of the elastic wave packet from the aperture of the optical beam. The corresponding equations for calculating the parameters of the output pulse were obtained by applying a rectangular pulse to the AODL input. It is proved that if the pulse duration at the AODL input is longer than the time of intersection of the optical beam by an elastic wave packet, then the pulse duration at its output will be equal to the duration of the input pulse. In the case when the duration of the input pulse is less than the time of crossing the optical beam by an elastic wave packet, the duration of the output pulse will be determined by the time of propagation of the elastic wave packet in the aperture of the optical beam. The obtained equations are confirmed by numerical calculations. The results of the numerical analysis were tested experimentally, which confirms the unequivocal adequacy of the proposed model of photoelastic interaction in an AODL.

Обсуждены схема и алгоритм функционирования акустооптического процессора (АОП), основными узлами которого являются акустооптический модулятор (АОМ), лазер и фотоприемник (ФП). Путем математического моделирования показано, что сигнал на выходе АОП содержит информацию о характеристиках АОМ, лазера и ФП. Постулирована возможность исследования характеристик одного из этих узлов при известных параметрах двух других по отклику АОП на детерминированное входное воздействие в виде прямоугольного импульса. Проведен краткий обзор известных методов измерения параметров лазера и ФП, отмечены некоторые ограничения в их применениях. Теоретически обоснована возможность использования особенностей АОП для измерения параметров инерционности ФП. Выведена формула для расчета отклика на выходе АОП на прямоугольное входное воздействие, которая использована для раздельной оценки времени пересечения оптического пучка упругим волновым пакетом и инерционности ФП. Также доказано, что путем использования короткого входного воздействия особенностей АОП можно использовать для определения конфигурации поперечного сечения лазерного пучка и закона распределения плотности потока мощности в нем. Результаты теоретических исследований апробированы численными расчетами и подтверждены экспериментальными измерениями.

The paper emphasizes that intensive utilization of the optical range increases the need for the development of new optoelectronic devices. Accordingly, there is a growth in the need for effective methods and tools to study photoelectric properties of semiconductor materials, including photo-detectors.In the paper we have analyzed the well-known methods and tools for measuring the photo-detector parameters, defined the restrictions in their applications, and proved that it is relevant to create a measuring system, the parameters of which are easily adapted to the study of photoelectric characteristics of a wide range of semiconductor materials, including photo-detectors.The scheme and principle of operation of the acousto-optic processor and the features of the photo-elastic effect are discussed, and it is proved that they can be used to form a light pulse of required duration and power. The expressions obtained for calculating the response at the acousto-optic processor output enable us to estimate separately the effects of time of crossing the optical beam by the elastic wave packet and the photo-detector inertia.The capability to determine the time of crossing the optical beam by the elastic wave packet and taking it into account as a device error has been substantiated. The proposed formulas have been tested and by numerical analysis based on the datasheet specifications of the FD-24K photodiode, the effectiveness of the obtained expressions has been convincingly proven.The inertia parameters of a particular sample of the FD-24K photodiode are experimentally studied. The emphasis is upon measuring the rise time of the transient response of the object under study. The exact rise time value of the transient response of the experimental FD-24K sample was approximately 7 μs, which is less than that indicated (≤10 μs) in the product certificate. In real life, such a measurement is necessary when selecting the photodiode pairs with identical parameters.By comparing the results of numerical analysis and experimental studies, it has been convincingly proven that the features of the photo-elastic effect can be used to construct a light pulse shaper with the required parameters.

The article deals with the peculiarities of various types of target detection with the use of radar stations in the organization of radio technical observation in the Navy and the methods have been proposed to determine some parameters for detecting a target during combat operations.

The features of the photoelastic effect are discussed and it is shown that they can be used to measure the parameters of a laser and a photodetector, which are the main units of any optoelectronic product. A brief review of the known methods for measuring the parameters of a laser and a photodetector is carried out, and some limitations in their application are noted. The possibility of using the features of the photoelastic effect for measuring the parameters of the inertia of the photodetector is theoretically substantiated. A formula for calculating the response at the output of an acousto-optic processor to a rectangular input action is derived and used to separately estimate the time of crossing the optical beam by an elastic wave packet and the inertia of the photodetector. It has also been proven that by choosing a short input action, the features of the photoelastic effect can be used to determine the configuration of the cross section of the laser beam and the law of the distribution of the power flux density in it. The results of theoretical studies have been tested by numerical calculations and confirmed by experimental measurements.

The properties of photoelastic effect and optical heterodyning for designing of high speed acousto-optic delay line for radio signals are used.

Особенности фотоупругого эффекта и оптического гетеродинирования использованы для построения электронно-управляемой акустооптической линии задержки радиосигналов.

Studies of the effect of lasers on metals have shown that the action of intense light beams leads to the formation of craters on metal surfaces. A considerable increase in hardness is often observed in the region of such craters; the hardness of low-carbon steels may reach 700 kg/mm2, which is considerably higher than that produced by other heat and mechanical treatments.