Dynamics of autodyne response formation in microwave generators

The paper presents results of studying the dynamics of autodyne response formation when switching on a radio-pulse microwave generator which is subject to the influence of its own reflection radiation. Basic relations for a step-wise calculation of autodyne response as a function of time delay, autodyne response time constant, distortion parameter and intrinsic parameters of the self-oscillating system are obtained. Calculation and analysis of peculiarities of autodyne signal generation by radio-pulse oscillator are conducted for the cases of motionless and moving reflecting object under relatively low, medium and high inertia properties of the oscillator if compared to the propagation time of the reflected radiation. Experimental research results that confirm conclusions of theoretical analysis are obtained for a common hybrid-integrated autodyne TIGEL-08 module of the 8-mm frequency-range implemented on a planar two-meza Gunn diodes and the same module stabilized by the external high-Q resonator. © 2013 Allerton Press, Inc

Analysis of signals of stabilized autodynes

Results of the autodyne signal analysis of the self-oscillating systems stabilized in frequency by the external high-quality cavity are given. The coupling between the main and stabilizing cavities is realized on the basis of a pass-reflective filter with a resistive link. Mathematical equations are obtained describing an autodyne response onto impact of the own radiated signal reflected from a target. The analysis of phase, amplitude, frequency and amplitude-frequency characteristics of the autodyne system is fulfilled. The calculation of an autodyne signal spectrum is discussed. A new type of nonlinear distortions of an autodyne signal is examined, which is caused by a frequency dispersion of an oscillating system of the stabilized autodyne. Advantages of the stabilized autodyne compared to the usual single-tuned autodyne oscillator are shown

Determination of autodyne oscillator parameters by the beating method

The research results of oscillator internal parameters influence the features of dynamic autodyne characteristics formation in the case of external oscillator signal influence are presented. The equivalent circuit with a single-circuit oscillating system is considered as a model of the autodyne oscillator. Abbreviated equations are obtained by an averaging method and then they are linearized for small disturbances in a vicinity of the steady-state mode. The obtained characteristics for the beating mode are compared with characteristics of autodynes for short-range radar technology. The essential differences in behavior of the oscillator with acting the external oscillator and the oscillator with acting the own reflected signal have been found. The physical sense of the frequency dispersion phenomenon for the autodyne frequency deviation in the vicinity of hypothetical “zero” beating is discovered. The research results of dynamic autodyne characteristics in the frequency conversion mode of signals modulated on amplitude or frequency are given. It is shown that to suppress the spurious harmonics of the beating frequency, it is advisable to take additional measures for generated frequency stabilization in autodyne frequency converters, for instance, using the external feedback in the oscillator or using the external high-Q resonator. The adequacy of theoretical conclusions is confirmed by results of experimental investigations of the hybrid-integrated module of 8 mm-range made on the basis of the planar two-meza Gunn diode. Oscillator characteristics obtained by the beating method are compared with results of investigation fulfilled with the help of modulation characteristics. It is shown that errors in experimental determination of dynamic characteristics of autodyne oscillators caused by frequency limitations of a pin-diode typical for the modulation characteristic method can be eliminated. Problems of practical application of obtained results in real radar systems using autodyne oscillators are discussed

Modulation characteristics of microwave autodyne oscillators

General relations for the analysis of autodyne and modulation characteristics are obtained in the form of differential equations with the retarded argument. Solutions for characteristics of frequency response of autodyne variations of the oscillation amplitude and phase as well as the auto-detecting signal of UHF oscillator under influence of the proper reflected radiation are derived. The solution of the same equation system is given for frequency responses of the modulation deepness of oscillation amplitude and frequency as well as the auto-detecting signal in the case of the reflection factor modulation by the high-frequency signal. Calculations of autodyne and modulation characteristics are fulfilled at different values of inherent parameters of UHF oscillators. Non-isochronous and non-isodromous properties of autodyne oscillators are investigated. Phenomena of frequency auto-detecting are considered. A method for dynamic properties determination is substantiated according to its modulation characteristics at the oscillation amplitude registration. The results of theoretical analysis are confirmed by experimental data obtained on the example of hybrid-integrated oscillator of 8mm-range on the Gunn diode

Theory of stabilized autodyne oscillators at the large reflected signal

Research results on autodyne oscillator stabilized by an external high-Q cavity are presented for the case of the large reflected signal, when amplitude of the reflected wave is commensurable with amplitude of natural oscillations. Expressions describing an autodyne response of the oscillator on the influence of the proper radiation reflected from a target are obtained. Calculations of amplitude, frequency and spectral characteristics of the autodyne system are performed. Conditions of exact tuning of the stabilized cavity are determined. Investigations of stabilized autodyne parameters at small distance to the reflected object are provided. It is shown that to expand the dynamic range of the autodyne system it is expedient to use the large coupling between cavities. Recommendations concerning practical application of the obtained results in the short-range radar are given

Влияние металлического стержня внутри сферической линзы Люнеберга на ее характеристики

The paper discusses the option of installing a load-bearing element inside a spherical Luneberg lens (LL). The presence of a metal element inside the LL will increase the structural rigidity of the spherical antenna and thereby expand the scope of use of the LL at various mobile communications and radar facilities with severe operating conditions. The influence of a metal rod inside the main spherical structure on the radiation pattern in two main planes in the linear polarization mode and on the diffraction pattern of the radiation field is estimated. The results of the analysis of the directional characteristics and the diffraction pattern of the LL radiation field were obtained using modeling in the Ansys Electronics Desktop (HFSS Design) working environment, as well as mathematical modeling using the Green tensor function method. At the same time, the obtained mathematical relations can be used in the future to solve the problem of finding the optimal size and position of a metal element in the sphere of LL. Denisov D. V., Noskov V. Ya. The influence of a metal rod inside a spherical Luneberg lens on its characteristics. Ural Radio Engineering Journal. 2022;6(2):160–185. (In Russ.) DOI: 10.15826/urej.2022.6.2.003. В работе обсуждается вариант инсталляции несущего элемента внутрь сферической линзы Люнеберга (ЛЛ). Наличие металлического элемента внутри ЛЛ позволит повысить конструктивную жесткость сферической антенны и тем самым расширить область использования ЛЛ на различных объектах подвижной связи и радиолокации с тяжелыми условиями эксплуатации. Приводится оценка влияния металлического стержня внутри основной сферической конструкции на диаграмму направленности в двух основных плоскостях в режиме линейной поляризации и на картину дифракции поля излучения. Результаты анализа характеристик направленности и дифракционной картины поля излучения ЛЛ получены с помощью моделирования в рабочей среде Ansys Electronics Desktop (HFSS Design), а также математическим моделированием с применением метода тензорных функций Грина. При этом полученные математические соотношения могут быть использованы в дальнейшем для решения задачи поиска оптимальных размеров и положения металлического элемента в сфере ЛЛ

Moving Object Signal Analysis of Autodyne Radars with Linear Types of Frequency

Представлены результаты исследования особенностей формирования сигналов автодинной системы ближней радиолокации с линейной частотной модуляцией для движущегося отражающего объекта. Получены основные соотношения и результаты вычисления автодинных сигналов для случаев, когда продолжительность их периода значительно больше времени запаздывания отраженного излучения, а также для случаев, когда данное неравенство не выполняется. Рассмотрены особенности сигналов для приближающегося и удаляющегося объекта. Экспериментальные данные получены на генераторе, выполненном на диоде Ганна 8‑мм диапазона с перестройкой частоты при помощи варикапа.General equations for analysis of the signal formation peculiarities are obtained for the autodyne short-range radar (ASRR) systems both for the case of the fixed and moving reflecting object, using arbitrary types of frequency modulation (FM). The developed mathematical model anticipates the interaction analysis of ASRR with the reflected emission at arbitrary ratio of the delay time τ of the reflected emission and the autodyne signal period Ta. Signal features for the oncoming and outcoming object are considered. The experimental data are obtained on the oscillator made on the 8mm-Gunn diode with the varicap frequency tuning. The fulfilled calculations and experimental investigations of ASRR signals for linear types of FM show that the autodyne frequency both for the moving and fixed reflector exactly corresponds to the frequency of transformed signal obtained in the case of the homodyne system. However, the presence of autodyne signal distortions requires the account in the signal processing devices under conditions, when the distance to the reflecting object is small, and the feedback parameter Cfb is commensurable to 1. The obtained results of autodyne characteristic research in the case when the autodyne signal period is commensurable or even less than delay time show that the distortion of autodyne signal at hypothetical keeping of the reflected amplitude decreases with distance growth. The calculations show that if the feedback parameter exceeds some boundary value even in several times, in higher operation zones of ASRR with FM operation can be provided with formation of quasi-harmonic signals. The obtained analysis results are developed and supplemented of results of known investigations, which were published in previous papers. Revealed regulations of signal formation in ASRR with FM have enough general characteristics and physical interpretation on the base of the step method known in systems with delay. In this connection, the obtained results in this paper can be used in the calculations of autodyne system signals made on semiconductor laser modules with FM

Optimal choice of prophylactic anticoagulant therapy for nonvalvular atrial fibrillation in the context of COVID-19 pandemic

Already at the very beginning of COVID-19 pandemic, it became known about the key clinical and pathogenetic significance of immunopathological reactions and disorders of hemostasis. Specific coagulopathy, microvascular thromboinflammatory organ damage, macrothrombosis and thromboembolism in the acute period of COVID-19, as well as secondary hemostasis disorders in convalescents, actualize the issues of caring patients with cardiovascular disease. COVID-19 not only increases the risk of thromboembolic events for patients with previously identified arrhythmias, but can also indirectly cause it (as a complication of infection or therapy). The aim of this work was to summarize the data and substantiate the optimal choice of prophylactic anticoagulant therapy for nonvalvular atrial fibrillation during the COVID-19 pandemic. Atrial fibrillation is not only the most common type of supraventricular tachyarrhythmia, but it is also the main underlying cause of more than half of cardioembolic stroke cases, which requires effective thromboprophylaxis. While maintaining the infectious danger for patients, the anticoagulant selection should take into account the possible dysfunctions and drug interactions during the initial infection or reinfection of COVID-19, as well as the possibility of rapid anticoagulant action reverse if surgery is required or bleeding develops. The optimal choice seems to be the use of dabigatran, which is characterized by the best safety profile for hepato- and nephrotoxicity, cytochrome P450-independent metabolism, and the presence of an antidote

Метод повышения разрешающей способности по дальности радиоимпульсных датчиков систем ближней радиолокации

The description of a new method for increasing the resolution of radio pulse sensors (RPS) designed for short- range radar systems (SRRS) for detecting and measuring motion parameters of location objects is presented. The essence of the method is that the controlled area of space with the targets located in it is periodically irradiated with probing radio pulses, and during their radiation, radio pulses reflected from the targets are simultaneously received and divided into two quadrature channels. Next, they are mixed with probing radio pulses, and the time-overlapping parts of these radio pulses are converted into the region of low Doppler frequencies in the form of two quadrature video pulses. Then, the quadrature video pulses received in these channels are sampled by amplitude, stored at multiple points in time and digitally processed according to the proposed algorithm. The method is implemented in the RPS made on the basis of a horn-lens antenna, a Doppler receiving and transmitting module with quadrature outputs of converted signals, a synchronization and pulse generation unit, as well as a digital signal processing unit. The RPS can be used in onboard (for example, automotive) SRRS designed to detect moving targets, measure the distance to them, as well as determine the speed and direction of movement. The results of experimental studies have been obtained on the example of the 8-mm autodyne RPS made on the basis of the oscillator on a planar Gann-diode. Bogatyrev E. V., Vishnyakov D. S., Ignatkov K. A., Noskov V. Ya. Method of increasing the range resolution of radio pulse sensors of short-r ange radar systems. Ural Radio Engineering Journal. 2023;7(2):166–190. (In Russ.) DOI: 10.15826/urej.2023.7.2.005.Представлено описание нового метода повышения разрешающей способности радиоимпульсных датчиков (РЛД), предназначенных для систем ближней радиолокации (СБРЛ) обнаружения и измерения параметров движения объектов локации. Суть метода состоит в том, что контролируемую область пространства с находящимися в ней целями периодически облучают зондирующими радиоимпульсами, причем во время их излучения одновременно принимают отраженные от целей радиоимпульсы и разделяют их на два квадратурных канала. Далее смешивают их с зондирующими радиоимпульсами, преобразуют перекрывающиеся по времени части этих радиоимпульсов в область низких доплеровских частот в виде двух квадратурных видеоимпульсов. Затем полученные в этих каналах квадратурные видеоимпульсы дискретизируют по амплитуде, запоминают во множестве моментов времени и подвергают цифровой обработке по предложенному алгоритму. Метод реализован в РЛД, выполненном на базе рупорно-линзовой антенны, доплеровского приемопередающего модуля с квадратурными выходами преобразованных сигналов, блока синхронизации и формирования импульсов, а также блока цифровой обработки сигналов. РЛД может найти применение в бортовых СБРЛ (например, автомобильных), предназначенных для обнаружения движущихся целей, измерения расстояния до них, а также определения скорости и направления движения. Результаты экспериментальных исследований получены на примере автодинного РЛД 8-мм диапазона, выполненного на основе генератора на планарном диоде Ганна. Богатырев Е. В., Вишняков Д. С., Игнатков К. А., Носков В. Я. Метод повышения разрешающей способности по дальности радиоимпульсных датчиков систем ближней радиолокации. Ural Radio Engineering Journal. 2023;7(2):166–190. DOI: 10.15826/urej.2023.7.2.005

Особенности сигналов от распределенных целей автодинного импульсного радиолокатора с линейной частотной модуляцией

Разработана математическая модель для описания сигналов автодинной системы ближней радиолокации (СБРЛ) с одновременной импульсной модуляцией (ИМ) амплитуды и линейной частотной модуляцией (ЛЧМ). Рассматриваются особенности формирования сигналов, полученных от распределенной цели в виде ансамбля произвольного числа точечных отражателей. Выполнены расчеты сигналов предложенным методом шагов для случая двух точечных отражателей на объекте локации, расположенных на различных расстояниях от СБРЛ. Установлены отличительные свойства сигналов, формируемых при приеме первого и последующих излучений, отраженных от цели. После посылки зондирующего излучения прием первого отраженного излучения от совокупности блестящих точек сопровождается формированием линейной суперпозиции сигналов от отдельных отражателей. Прием последующих отражений вызывает появление комбинационного взаимодействия сигналов отдельных отражателей. Характер и величина такого взаимодействия определяется величиной параметра обратной связи автодинной СБРЛ, зависящего от величин девиации частоты и времени запаздывания отраженного излучения. Результаты экспериментальных исследований автодинной СБРЛ c одновременной ИМ амплитуды и ЛЧМ получены при использовании генераторного модуля, выполненного на диоде Ганна 8-миллиметрового диапазона. Носков В. Я., Богатырев Е. В., Галеев Р. Г., Вишняков Д. С. Особенности сигналов от распределенных целей автодинного импульсного радиолокатора с линейной частотной модуляцией. Ural Radio Engineering Journal. 2022;6(4):351–377. DOI: 10.15826/urej.2022.6.4.001.