Four-antenna amplitude direction finder: statistical synthesis and experimental research of signal processing algorithm

The subject of this study is the algorithms for measuring the angular positions of radio emission sources. The goal of this study is to develop an improved algorithm for signal processing in amplitude direction finders that will provide several unambiguous measurement angles at high steepness of the discrimination characteristic by combining measurements of systems with different widths of antenna patterns. The task: to develop an optimal signal processing algorithm for a four-antenna amplitude direction finding system, two antennas of which have a wide radiation pattern and the other two have a narrow one; to test the overall performance of the resulting algorithm by simulating the direction finder; to develop and conduct a study of an experimental model of a four-antenna direction finder, which includes two antennas with wide radiation patterns, two antennas with narrow radiation patterns, radio frequency paths, and a signal processing unit that implements the developed algorithm; to analyze the effectiveness and features of the application of the developed algorithm, and to compare the results of simulation modeling and experimental research. The methods used are statistical methods and optimal solutions for solving problems of statistical synthesis of signal processing algorithms in passive radio systems, computer simulation modeling methods, and experimental research methods. The following results were obtained. The algorithm for signal processing in a four-antenna direction finding system was synthesized using the maximum likelihood method. By simulation modeling, the overall effectiveness of measurement integration in multi-antenna amplitude direction finders was confirmed, and the peculiarities of the synthesized algorithm application were revealed, namely, the need to introduce additional proportionality coefficients into the measurement channels. During the experimental studies of the developed model of the direction finder, the results of the simulation modeling were confirmed. Conclusions. To determine the direction of radiation sources by amplitude direction finders, it is advisable to simultaneously use systems with wide and narrow antenna patterns, the measurements of which are combined by the proposed algorithm. This makes it possible to simultaneously expand the range of unambiguous measurement angles and increase the accuracy of measurements within the equal-signal zone. The disadvantage of using the algorithm is the nonlinear form of the obtained discrimination characteristics and the need to determine additional proportionality coefficients heuristically

Optimal Method for Polarization Selection of Stationary Objects Against the Background of the Earth’s Surface

Within the maximum likelihood method an optimalalgorithm for polarization target selection against the backgroundof interfering signal reflected from the earth’s surface is synthesized. The algorithm contains joint operations of spectralinterference rejection and their polarization compensation bymeans of certain combinations of interchannel subtraction ofsignals of different polarizations. The physical features of theelements of the polarization scattering matrix are investigatedfor the technical implementation of the synthesized algorithm

Signal Processing Algorithm for Monopulse Noise Noncoherent Wideband Helicopter Altitude Radar

Radio altimeters are an important component of modern helicopter on-board systems. These devices currently involve the use of narrowband deterministic signals, that limits their potential technical characteristics. Given the significant breakthrough in the development of wideband and ultra-wideband radio electronics, it is promising to create on-board radio complexes capable of obtaining the necessary information using wideband stochastic signals. At the same time, when developing such complexes, it is important to use optimal synthesis methods for radio systems, which will allow optimal signal processing algorithms and potential accuracy parameters to be obtained. In this work, the algorithm to measure flight altitude for a helicopter or an unmanned aerial vehicle based on the processing of wideband and ultra-wideband pulsed stochastic signals is synthesized for the first time by the maximum-likelihood method. When formulating the problem, the mathematical model of the signal and observation is specified, and their statistical characteristics are investigated. The peculiarity of the synthesis task is the use of a noise pulse transmitter, which implements the function of an underlying surface illuminator, as well as considering the signal structure destruction during its radiation, propagation, and reflection. This signal shape destruction makes it impossible to synthesize a radar with internally coherent processing when working on one receiving antenna. In accordance with the synthesized algorithm, a simulation model of a pulsed radar with a stochastic probing signal has been developed and the results of its modeling are presented

Signal Processing Algorithm for Monopulse Noise Noncoherent Wideband Helicopter Altitude Radar

Radio altimeters are an important component of modern helicopter on-board systems. These devices currently involve the use of narrowband deterministic signals, that limits their potential technical characteristics. Given the significant breakthrough in the development of wideband and ultra-wideband radio electronics, it is promising to create on-board radio complexes capable of obtaining the necessary information using wideband stochastic signals. At the same time, when developing such complexes, it is important to use optimal synthesis methods for radio systems, which will allow optimal signal processing algorithms and potential accuracy parameters to be obtained. In this work, the algorithm to measure flight altitude for a helicopter or an unmanned aerial vehicle based on the processing of wideband and ultra-wideband pulsed stochastic signals is synthesized for the first time by the maximum-likelihood method. When formulating the problem, the mathematical model of the signal and observation is specified, and their statistical characteristics are investigated. The peculiarity of the synthesis task is the use of a noise pulse transmitter, which implements the function of an underlying surface illuminator, as well as considering the signal structure destruction during its radiation, propagation, and reflection. This signal shape destruction makes it impossible to synthesize a radar with internally coherent processing when working on one receiving antenna. In accordance with the synthesized algorithm, a simulation model of a pulsed radar with a stochastic probing signal has been developed and the results of its modeling are presented

Algorithm for Determining Three Components of the Velocity Vector of Highly Maneuverable Aircraft

We developed a signal processing algorithm to determine three components of the velocity vector of a highly maneuverable aircraft. We developed an equation of the distance from an aircraft to an underlying surface. This equation describes a general case of random spatial aircraft positions. Particularly, this equation considers distance changes according to an aircraft flight velocity variation. We also determined the relationship between radial velocity measured within the radiation pattern beam, the signal frequency Doppler shift, and the law of the range changing within the irradiated surface area. The models of the emitted and received signals were substantiated. The proposed equation of the received signal assumes that a reflection occurs not from a point object, but from a spatial area of an underlying surface. It fully corresponds to the real interaction process between an electromagnetic field and surface. The considered solution allowed us to synthesize the optimal algorithm to estimate the current range and three components {Vx,Vy,Vz} of the aircraft’s velocity vector V→. In accordance with the synthesized algorithm, we propose a radar structural diagram. The developed radar structural diagram consists of three channels for transmitting and receiving signals. This number of channels is necessary to estimate the full set of the velocity and altitude vector components. We studied several aircraft flight trajectories via simulations. We analyzed straight-line uniform flights; flights with changes in yaw, roll, and attack angles; vertical rises; and landings on a glide path and lining up with the correct yaw, pitch, and roll angles. The simulation results confirmed the correctness of the obtained solution

Структурна схема багаточастотного радіометричного комплексу виявлення БПЛА в різних метеорологічних умовах

Проблематика. В Україні та світі набули стрімкого розвитку технології виробництва безпілотних літальних апаратів (БПЛА) різного класу. Малі за масо-габаритними характеристиками та майже невидимі для більшості інформаційно-вимірювальних систем БПЛА стали використовуватись в різних галузях – від народного господарства до мультимедіа та реклами. Разом з корисним їх використанням з’явились нові небезпеки та інциденти – зіткнення БПЛА з людьми, спорудами, пам’ятниками культури, перевезення кримінальних товарів, терористичні акти, польоти над забороненими ділянками та в межах аеропортів. Виявлення БПЛА та контроль їх переміщення у населених пунктів та поблизу критичних об’єктів стає однією з найважливіших задач служб контролю руху повітряним простором. Існуючі системи оптичного, акустичного та радіолокаційного діапазонів не спроможні ефективно виконувати такі задачі в складних метеорологічних умовах. У якості доповнення до вже розвинутих систем виявлення пропонується використовувати радіометричні системи, що реєструють власне радіотеплове випромінювання БПЛА. Авторами були розроблені теоретичні основи побудови багаточастотних комплексів, необхідні для конкретизації їх структурних схем. Мета досліджень. Розробка схеми багаточастотного радіометричного комплексу виявлення БПЛА в різних метеорологічних умовах на основі оптимальних алгоритмів. Методика реалізації. Аналіз досвіду розробки радіометричних систем та методів боротьби з флуктуаціями коефіцієнту підсилення приймачів, оптимальні операції обробки сигналів власного радіотеплового випромінювання, дослідження ймовірнісних характеристик виявлення та аналіз вітчизняного ринку розробників НВЧ техніки дозволять розробити схему багаточастотного радіометричного комплексу, що виконуватиме надійні вимірювання в різних метеорологічних умовах. Результати досліджень. Запропоновано структурну схему чотирьохчастотного радіометричного комплексу, що може бути реалізований на практиці та здатний виконувати надійні вимірювання в різних метеорологічних умовах. У якості резонансних частот налаштування радіометричних приймачів були обрані частоти 10 ГГц, 20 ГГц, 35 ГГц і 94 ГГц. Для заданої конструкції та характеристик приймачів розраховані ймовірності виявлення БПЛА в залежності від дальності його польоту. Висновки. З результатів аналізу існуючих досягнень розвитку радіометричних систем в Україні та наявної на ринку елементної бази мікрохвильових компонентів випливає, що діапазон Ku та K має найгірші характеристики просторової роздільної здатності, але є всепогодними. Діапазони Ka і W мають високу чутливість до радіотеплового випромінювання на тлі ясного неба, але вони повністю «сліпі» при хмарній атмосфері та в дощ. Результати розрахунку відстаней виявлення з імовірністю 0,9 лежать у діапазоні від 1 до 3 кілометрів в залежності від стану атмосфери. Ці результати збігаються з відомими дальностями виявлення оптичних, акустичних та радіолокаційних систем, але при цьому обрані параметри приймачів не відповідають потенційним світовим досягненням і можуть бути покращені.Background. Technologies for the production of unmanned aerial vehicles (UAVs) of various classes are rapidly developing in Ukraine and the world. Small in terms of weight and dimensions and almost invisible for most information and measurement systems, UAVs began to be used in various industries - from the national economy to multimedia and advertising. Together with their useful application, new dangers and incidents have appeared - a collision of UAVs with people, structures, cultural monuments, the transportation of criminal goods, terrorist acts, flights over prohibited areas and within airports. UAV detection and control of their movement in populated areas and near critical objects are becoming one of the most important tasks of air traffic control services. The existing systems of the optical, acoustic and radar ranges cannot effectively perform such tasks in difficult meteorological conditions. As an addition to the already developed detection systems, it is proposed to use radiometric systems that register the UAV's own radio-thermal radiation. The authors have developed the theoretical foundations for the construction of multifrequency complexes necessary for the specification of their structural schemes. Objective. The purpose of the paper is development of a scheme for a multi-frequency radiometric complex for detecting UAVs in different meteorological conditions based on optimal algorithms. Methods. Analysis of the experience in the development of radiometric systems and methods for dealing with fluctuations in the gain of receivers, optimal operations for processing signals of intrinsic radio-thermal radiation, investigations of the probabilistic characteristics of detection and analysis of the domestic market of microwave technology developers will make it possible to develop a scheme of a multifrequency radiometric complex that will perform reliable measurements in various meteorological conditions. Results. A block diagram of a four-frequency radiometric complex is proposed, which can be implemented in practice and is capable of performing reliable measurements in various meteorological conditions. The frequencies 10 GHz, 20 GHz, 35 GHz, and 94 GHz were chosen as the resonant frequencies for tuning the radiometric receivers. For a given design and characteristics of receivers, the probabilities of detecting a UAV were calculated depending on the range of its flight. Conclusions. From the results of the analysis of the existing achievements in the development of radiometric systems in Ukraine and the elemental base of microwave components available on the market, it follows that the Ku and K bands have the worst characteristics of spatial resolution, but are all-weather. The Ka and W bands are highly sensitive to radio-thermal radiation against the background of a clear sky, but are completely "blind" in a cloudy atmosphere and in rain. The results of calculating the detection ranges with a probability of 0.9 lie in the range from 1 to 3 km, depending on the condition of the atmosphere. These results coincide with the known detection ranges of optical, acoustic and radar systems, but the selected parameters of the receivers do not correspond to potential world achievements and can be improved

Optimal Method for Polarization Selection of Stationary Objects Against the Background of the Earth’s Surface

Within the maximum likelihood method an optimalalgorithm for polarization target selection against the backgroundof interfering signal reflected from the earth’s surface is synthesized. The algorithm contains joint operations of spectralinterference rejection and their polarization compensation bymeans of certain combinations of interchannel subtraction ofsignals of different polarizations. The physical features of theelements of the polarization scattering matrix are investigatedfor the technical implementation of the synthesized algorithm

Optimal Method for Polarization Selection of Stationary Objects Against the Background of the Earth’s Surface

Within the maximum likelihood method an optimal algorithm for polarization target selection against the background of interfering signal reflected from the earth’s surface is synthesized. The algorithm contains joint operations of spectral interference rejection and their polarization compensation by means of certain combinations of interchannel subtraction of signals of different polarizations. The physical features of the elements of the polarization scattering matrix are investigated for the technical implementation of the synthesized algorithm