Journal of the Russian Universities. Radioelectronics / Известия высших учебных заведений России. Радиоэлектроника
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Модифицированный алгоритм Банкрофта для систем мультилатерации
Get PDFIn multilateration systems, Bancroft algorithm is often used to estimate the location of objects. This algorithm is synthesized for satellite navigation systems. The algorithm allows to obtain the location estimation by means of direct method and does not require significant computing costs. These properties set it apart from algorithms using optimization approaches. However, according to the results of computer simulation, the accuracy of estimation yielded by the algorithm can be several times worse than potentially enable one. The article proposes a method for modifying the Ban-croft algorithm. Modification involves refining the Bancroft estimates by applying the method of small perturbations. The article shows that the use of the proposed modification allows to increase the accuracy of estimates by 2.5–3 times and to make it equal to the Cramer-Rao boundary. At the same time, the complexity of the modified algorithm grows in-significantly.В системах мультилатерации для оценки местоположения (МП) объектов часто используется алгоритм Банкрофта, синтезированный для оценки МП объектов в спутниковых системах навигации. Алгоритм позволяет прямым способом получить оценку МП и не требует больших вычислительных затрат при реализации. Данные свойства выгодно отличают этот алгоритм от алгоритмов, работающих на основе решения оптимизационных задач. Однако, как показывают результаты математического моделирования, точность получаемых с помощью алгоритма оценок может быть в несколько раз ниже, чем потенциально достижимая. Предлагается способ модификации алгоритма Банкрофта, который состоит в уточнении оценок Банкрофта путем применения метода малых возмущений. Показано, что использование предлагаемой модификации позволяет в 2,5–3 раза увеличить точность оценок МП объекта и сделать ее равной потенциально достижимой. При этом сложность модифицированного алгоритма возрастает незначительно
Исследование путей расширения динамического диапазона широкополосных приемных устройств СВЧ в многосигнальном режиме
Get PDF The article investigates ways to expand the dynamic range of broadband microwave receiving devices. The task is to lim-it the output signals while increasing the upper boundary of the dynamic range by the criterion of the thirdorder inter-modulation component suppression. The main relations determining the dynamic range boundary conditions are pre-sented. Experimental studies of three variants of constructing the broadband microwave receiver output path in two-ton mode of operation are carried out for:– an output amplifier with a point of 1 dB of output power compression at the level corresponding to safe output power;– a powerful output amplifier with a passive diode limiter on the output;– a powerful output amplifier with an automatic attenuation adjustment circuit connected to its input.The measurement results of the magnitude of intermodulation distortions suppression and output power are presented as a function of the input signal level for various nonlinear elements. Based on the analysis of the measured characteristics, an optimal technical solution is found for constructing an output path. The dynamic range is extended by more than 20 dB. Suppression of intermodulation components of the third order exceeds 60 dB. Effective functioning of the broadband receiver in multisign mode is ensured
Полосовой активный RC-фильтр c линейно перестраиваемой добротностью
Get PDFThis article provides a technique for design and simulation of an active second order band-pass filter with lineal tuning of Q-factor and independent tuning over a wide range of resonant frequency and transfer coefficient. The tunable band-pass RC-filter is required for selective processing of electric signals in radio engineering systems and devices, as well as in in-formation measuring systems, the acoustic and hydro acoustic equipment, including devices for noise and vibration analysis. The band-pass RC-filter is required in equalizers for allocation of useful signals.It is shown that the filter is constructed on the basis of the active second order correcting link with the use of tunable RCcircuit T-bridge. Calculation formulas for filter parameters are received, i.e. resonant frequency, polar Q-factor and transfer coefficient. It is shown that in the filter circuit these parameters can independently be tunable over a wide range. Resonant frequency of the filter is tuned by means of dual variable resistors with the Q-factor and transfer coefficient remaining constant.Polar Q-factor is regulated by change of resistance of the variable resistor with transfer coefficient and resonant frequency remaining constant. The transfer coefficient changes by means of another variable resistor.The conclusions of expressions for the tuned parameters of the suggested circuit of the active band-pass RC-filter confirming the research are provided, as well as the filter frequency characteristics and tunable parameter diagrams. Filter implementation is supported by simulation with the use of MicroCap10 software
МОДЕЛИРОВАНИЕ ЭЛЕМЕНТАРНОЙ ЯЧЕЙКИ ОТРАЖАТЕЛЬНЫХ АНТЕННЫХ РЕШЕТОК НА КОЛЬЦЕВЫХ ЩЕЛЯХ
Get PDFThe ring-slot-element cell for reflectarray antennas is investigated. The mathematical model of the unit cell is based on the integral equation that is solved by the moment method with the use of the spectral domain Green’s function. Coaxial-line higher modes expressed in terms of cylindrical functions are used as the basis for magnet-current representation. It is shown that “stricken” frequencies at which resonance modes occur are an inherent part of slot elements. These frequencies are determined by the Green’s function poles. Moreover, the lowest resonance mode may occur in the operating band under certain conditions. Reflection-phase dependencies on the ring-slot size are provided, demonstrating that at “stricken” frequencies the unit cell does not operate properly. Field plots are presented, which show that the resonance-mode field distribution on the ring slot is significantly different from the normal-mode field distribution. It is found that the “stricken” frequencies might be shifted beyond the operating band by means of thorough selection of unit-cell geometric parameters
СИСТЕМА И АЛГОРИТМ ИНТЕЛЛЕКТУАЛЬНОЙ ОБРАБОТКИ И АНАЛИЗА БИОМЕДИЦИНСКИХ СИГНАЛОВ В СИСТЕМАХ УДАЛЕННОГО МОНИТОРИНГА СОСТОЯНИЯ ЗДОРОВЬЯ ЧЕЛОВЕКА
Get PDFContinuous and steady running of health status remote monitoring systems is essential not to omit episodes of acute exacerbation of chronic disease. Running time of such systems is largely determined by performance capabilities of the patient's wearable system elements. To ensure its long-term operation and efficient performance, the monitoring system must have multilayered structure with the elements realizing recording and picking off biomedical signals, signal processing and analysis, estimation of patient current condition, dynamics of the disease and its prognosis. For this purpose, it is necessary to use smart monitoring algorithms. A specific feature of such algorithms is change of the number of channels used for biomedical signal recording and processing according to the change of patient’s condition. To detect the exacerbation first symptoms by means of the patient's wearable computer, additional channels are activated for recording biomedical signals used to evaluate the expanded complex of diagnostically significant parameters of the disease and their integration when specifying the patient's condition. The system and intelligent monitoring algorithm is tested with the use of heart rate remote control and atrial fibrillation episode detection system. The testing results of the developed system and algorithm are discussed
Температурная коррекция широкополосных детекторов мощности на основе низкобарьерных диодов
Get PDFThe article is devoted to investigation of microwave power converter temperature dependence caused by changes in the current-voltage characteristic of diodes. The analytical expressions are given for such diode parameters as junction resistance and diode saturation current that allow to estimate temperature influence on diode detector output voltage. This paper presents a comparison of two methods, i.e. correlation based on a terminological method that works in con-junction with an arithmetic-logical mechanism. The first method implies that the temperature stabilizes by use of identical pair of diodes one of which compensates for temperature-induced changes of the second diode junction resistance. The second method involves formation of correction factors that allow performing temperature correction of measurement results in a wide range of capacities. Based on the conducted temperature tests of microwave power meters with the use of a temperature sensor in the microwave unit, the thermal correction algorithm was implemented. It allows to reduce the changes in the readings from ±15 to ±1.5%. Data from the results of experimental studies that can be used in measuring microwave equipment of various types. The results of experimental studies of detectors based on low-barrier diodes ZB-28 with a boundary speed exceeding 100 GHz and a tangential sensitivity of 1 nW are presented
РАЗРАБОТКА ТОПОЛОГИИ КОМПАКТНЫХ КВАЗИЭЛЛИПТИЧЕСКИХ ПОЛОСОВЫХ МИКРОПОЛОСКОВЫХ ФИЛЬТРОВ
Get PDFThis paper considers an algorithm for development of the sixth order compact microstrip bandpass filters with quasi-elliptic characteristics. The proposed technique is applied for synthesis of two filters for the L- and X-band. The recursive computational approach is employed to obtain the coupling matrix with simple topological implementation. Next, the full-wave transmission line analysis based on spectral-domain method of moments is applied for calculation of coupled microstrip resonator eigen frequencies. This approach is then used to compute magnitude and sign of the coupling coefficient for basic coupled resonator configurations. Finally, two quasi-elliptic filter topologies are synthesized and structure optimization in Ansys HFSS is performed. As a result, prototypes of the developed microstrip filters are manufactured and measured
ЦИФРОВАЯ ОБРАБОТКА ЭНДОСКОПИЧЕСКИХ ИЗОБРАЖЕНИЙ ДЛЯ СИСТЕМ ПОДДЕРЖКИ ВРАЧЕБНЫХ РЕШЕНИЙ
Get PDFThe purpose of this research is to create new automatic methods for endoscopic image digital processing, ensuring their high ergonomics and the possibility of effective use in clinical decision support systems. As the result of investigation, the following methods were proposed: the detection and removal of specular highlights; compensation of radial and tangential geometric distortions; the mosaic panorama creation from the input video stream with low level of detail; brightness and contrast enhancement, providing simultaneous successful correction of both dark and bright areas of the image (uneven contrast) without significant underlining of the noise component typical for the existing nonlinear contrasting methods, especially in low-detail image areas; custom color correction based on linear transformation matrix taking into account endoscopic image characteristics and making it possible to customize color palette according to the physician individual preferences. The methods considered were successfully tested on real endoscopic images at the department of innovative medical devices of the Korean Electrotechnological Research Institute. The test results demonstrate their effectiveness and applicability in clinical decision support systems
ПРИМЕНЕНИЕ БЕСТЕСТОВЫХ МЕТОДОВ ДЛЯ ОЦЕНКИ СОСТОЯНИЯ РАДИОКАНАЛА
Get PDFThe possibilities of increasing the data rate of adaptive HF communication systems by reducing redundancy in the form of test signals used for its operation are considered. The problem is currently pressing due to increasing demands of modern adaptive data transmission systems to efficient use of allocated frequency-time resource of radio channel. For the problem solution, methods based on the analysis of the received information signal, taking into account the used signal-code construction, are proposed. Approaches for solving problems of non-test adaptive signals correction and channel state estimation in serial data communication systems using convolutional encoder are proposed. Search algorithm for segments used for channel impulse response and equalizer coefficients calculation is shown. In this case, neither a change in decoding algorithms nor calculating of equalizer impulse response is required. Expressions for estimation of the bit error rate for a convolution encoder of general form are given. The presented approaches maintain operating of adaptive HF data transmission systems in channels with intersymbol interference, ensuring the operative change of its parameters when the state of the radio channel changes significantly reducing the use of test signals, or completely abandoning them
Анализ эффективности гетерогенных видеоинформационных систем на основе критерия доминирования
Get PDFThe approaches to the evaluation of the efficiency of the functioning of heterogeneous video information systems are considered. It is shown that the hierarchy model as a quantitative description of the structural and functional organization can serve as a means of analyzing information flows and system efficiency in terms of graph theory. The criterion of dominance for the evaluation of the efficiency of heterogeneous video information systems is analytically presented. It is shown that in the loaded graph of a heterogeneous system the weights of individual nodes represent the efficiency of this node, and with its increase the degree of influence (dominance) of this node on the remaining nodes of the system and on the system as a whole grows, and conversely, with a decrease in the weight of the node it rises its dependence on other nodes. The influence of the length of interstitial paths on the efficiency of the system is taken into account, taking into account the partial loss of information during its propagation through the graph. Numerical calculations of the efficiency of systems based on the dominance criterion are given, the results of which confirm the indicated theoretical positions.Рассмотрены подходы к оценке эффективности функционирования гетерогенных видеоинформационных систем. Показано, что модель иерархии как количественное описание структурнофункциональной организации может служить средством анализа информационных потоков и эффективности системы в терминах теории графов. Аналитически представлен критерий доминирования для оценки эффективности гетерогенных видеоинформационных систем. Показано, что в нагруженном графе гетерогенной системы веса отдельных узлов представляют эффективность этого узла, причем с его увеличением растет степень влияния (доминирования) данного узла на остальные узлы системы и на систему в целом, и обратно, со снижением веса узла повышается его зависимость от других узлов. Рассмотрено влияние длины межузловых путей на эффективность системы с учетом частичной потери информации при ее распространении по графу. Приведены численные расчеты эффективности систем на основе критерия доминирования, результаты которых подтверждают указанные теоретические положения