Journal of the Russian Universities. Radioelectronics / Известия высших учебных заведений России. Радиоэлектроника
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Синтез временно́го дискриминатора следящего контура измерения запаздывания спутникового высотомера
Get PDFThe article deals with the study of quasi-optimal TOA discriminator of an onboard echo-signal tracker of the altimeter carried by a space vehicle. In modern space-based altimeters, final data processing is imposed on the ground-based center receiving information from the spacecraft through a telemetry line, while the main task of an onboard delaylocked loop is to reliably retain the received echo-signal within the tracking window. The optimum discriminator of an onboard loop providing the potential accuracy of time measurement can appear difficult to implement. In the discriminator considered an error signal is proportional to the time mismatch between the half power point of the received power pattern and the tracking window. The equation for the equivalent time fluctuation variance is derived. It is also found that the discriminator proposed is as good at tracking precision as the maximum-power-point discriminator and maximums teepness discriminator, being at the same time much more attractive in terms of hardware complexity. The theoretical results are well consistent with the computer simulation. This simulation is performed both directly and using different methods of censoring the error signal at the discriminator output to effectively neutralize possible abnormal errors that are not taken into account by theoretical analysis
Анализ влияния нестабильности сигнала синхронизации на замещение локального контента для DVB-T2
Get PDFThe article is aimed at specifying criteria of synchronization signal inaccuracy when DVB-T2 system local content re-placement cannot be carried out. Some settings of digital information stream are set as the initial data. The first part of the article specifies network delay calculation method. The second part of the article considers the signal cycle instability impact on estimation of local content device delay during its insertion in global information flow. Network delay saw-toothlike dependence on time is revealed, statistical parameters of synchronization signal instability are specified. The third part of the article deals with analysis of method of substitution of two independent information flows by regionali-zation device. A model of T2 superframes comprising baseband frames (BB frames) which belong to different physical layer pipes (PLP) is described. The conditions under which the local information insertion becomes impossible are de-fined. Besides, the article considers other reasons of failure during single frequency networks (SFN) processing of local content insertion dealing with synchronization error at different stages of information flow digital content generation and delivery to DVB-T2
Сравнение статистических характеристик оценок доплеровской деформации и задержки сигнала с результатами узкополосной модели
Get PDFNarrowband approximation of Doppler effect by a frequency shift is inappropriate for some problems of radiolocation, hydro acoustics or passive location. In this case it is necessary to use Doppler stretch (time-scaling) as a signal parameter. Statistical performance of joint Doppler stretch and delay for arbitrary spectral width signal without narrowband approximations is derived in this paper.Narrowband and wideband parameters relations are investigated for triangle impulse with linear spectral modulation. Besides, Fisher Information Matrices (FIM) differences are analyzed. In the narrowband limit consideration of results in well-known FIM of Doppler shift and delay estimation are proposed. Another feature of wideband FIM is reference time dependence on time delay variance. Transition from Doppler stretch to Doppler frequency shift considering narrowband limitations results in translation invariant FIM.The article shows that reference time variance of delay estimation is related to estimated parameter modification and velocity influence on delay. Also, estimation variances in narrowband signal model differ from wideband parameter variances by magnitude of spectrum width to central frequency ratio. Изучаются статистические характеристики совместных оценок доплеровской деформации и задержки сигнала с произвольной шириной спектра, т. е. без допущений узкополосной модели. Исследован переход между параметрами узкополосной и широкополосной моделей на примере треугольного импульса с линейной частотной модуляцией, проведен анализ отличий в элементах информационных матриц. Проанализирована неинвариантность дисперсии оценки масштаба/задержки к выбору начала отсчета и приведено объяснение причин указанного эффекта.Показано, что неинвариантность дисперсии оценки задержки сигнала к выбору начала отсчета связана с изменением оцениваемого параметра и влиянием скорости цели на задержку. Полученные дисперсии оценок узкополосной модели совпадают с результатами широкополосной модели с точностью до поправки порядка отношения ширины спектра к центральной частоте.
ШИРОКОПОЛОСНАЯ СВЧ-АНТЕННА ВИВАЛЬДИ С ВОЗБУЖДЕНИЕМ КОПЛАНАРНОЙ ЛИНИЕЙ
Get PDFNowadays Vivaldi antennas are used as directional emitters with matching and balancing device at the input. As a rule, these devices cause additional losses in case of broadband operation. Besides, the use of the device leads to radiator pattern distortions, especially when operating in a wide frequency range. Stringent operating requirements (wide operating temperature, high humidity, salt fog, vibration, etc.), make the choice of proper chip very complicated. The aim of the study is to develop a slot antenna with a 50-ohm port at the input, which would be easy to manufacture and operate, while maintaining high gain in a wide frequency range. As is known, the field structure in the coplanar line is close to the field structure in the slit field close to it. As is known, the field structure in the coplanar line is similar to the field structure in the slot line. Using mathematics for such fields, means of electrodynamic modeling and numerical calculation, a system is developed that consists of two Vivaldi antennas fed by one coplanar line. Thus, the emitter has a close to a circular pattern and low losses in the structure of feeding, matching and balancing, the functions of which are performed by the coplanar line. The results are given for the frequency range of 1-6 GHz. The device as a whole is a dielectric substrate with radiating structure made as double-sided metallization. Finline-based emitters are acceptable to use for operation in higher frequencies. Antenna has low manufacturing cost and it is easy to repeat. Currently the authors are continuing work on the study of the use of such elements as part of antenna arrays
Механизмы формирования гетерофазных сегнетоэлектрических пленок цирконата-титаната свинца
Get PDFAn experimental and theoretical study of the formation processes of "impurity" phase inclusions in ferroelectric oxides is carried out via example of polycrystalline lead zirconate-titanate (PZT) films. A feature of these compositions is relatively high volatility of lead oxides, which can lead to deficiency of these components in the composition of the ferroelectric film formed during high-temperature crystallization. To avoid lead losses, some excess is added to the solution in the process of synthesis. Experimental samples of PZT films are obtained using sol-gel method with different contents of lead oxide, the crystallization of the ferroelectric phase of the films is carried out in air at 600 °C. In the films, the inclusions of lead oxide impurity phase are found, and the size distribution of these inclusions are obtained. Model concepts are presented and a system of equations is proposed describing the dispersed inclusions formation kinetics of new phases of different stoichiometric composition at the interfaces in polycrystalline films of multicomponent ferroelectric oxides due to bulk diffusion and grain-boundary segregation. Comparison of the experimental data with the theoretical model gives qualitative agreement. The approach generality makes it possible to extend the model to other systems of multicomponent ferroelectric polycrystalline materials
Взаимная индуктивность двух прямоугольных компланарных контуров с симметричным внутренним расположением
Get PDFThe expediency of developing expressions for mutual inductance of rectangular and square coplanar contours is caused by configuration of frame antennas typical for RFID-technologies. Expressions presented in this article are aimed at simplifying calculation of induction coefficients when designing loop antennas. Expressions for mutual inductance of rectangular coplanar contours with symmetrical internal arrangement are obtained on the basis of the method of sections. It is shown that under certain conditions the expressions obtained can be reduced to intrinsic inductances of the square and rectangular frames encountered in antenna configurations. The analysis allows to estimate regions of resonance frequencies of frame receiving antennas. Simultaneously, a comparative analysis of a number of expressions for the intrinsic inductance of rectangular and square frames is performed, and attention is drawn to the difference in estimates. Recommendations for clarifying square contour external inductance are provided.Целесообразность вывода выражений для взаимной индуктивности прямоугольных и квадратных компланарных контуров обусловлена конфигурацией рамочных антенн, характерных для RFID-технологии. Представленные в данной статье выражения направлены на упрощение расчета коэффициентов индукции при проектировании рамочных антенн. Получены выражения для взаимной индуктивности прямоугольных компланарных контуров с симметричным внутренним расположением на основе метода участков. Показано, что полученные выражения при определенных условиях могут быть сведены к собственным индуктивностям квадратных и прямоугольных рамок, встречающихся в конфигурациях антенн. Предпринятый анализ позволяет оценивать области резонансных частот рамочных приемных антенн. Одновременно произведен сопоставительный анализ ряда выражений для собственной индуктивности прямоугольных и квадратных рамок и обращено внимание на различие в оценках. Даны рекомендации по уточнению внешней индуктивности квадратного контура