scholarly journals INCREASE IN ACCURACY OF MEASURING AIR OBJECTS ANGULAR COORDINATES DURING MULTICHANNEL RECEPTION OF RADIO-LOCATION SIGNAL

Author(s):  
O. Kuznietsov ◽  
O. Kolomiitsev ◽  
S. Yarovyy ◽  
R. Oliinyk ◽  
Y. Zhivetc

Radars with a phased array antenna (PAA) which performs multi-channel radar signal reception are effective means of obtaining radar information about air objects in difficult conditions of air and jamming environment. Radar surveillance for radars with PAA is accompanied by a significant negative effect of tropospheric inhomogeneity, which causes a decrease in the accuracy of measurements of azimuth angles and air object‟s position due to fluctuations of the phase front of the received wave reflected from an air object. According to the results of research, the hypothesis of a normal distribution law of these fluctuations is accepted. The paper presents the results of estimating the root mean square errors of measuring the angular coordinates of the air object, which occur if the fluctuations of the phase front of the received signal‟s wave are not taken into account and analyzes the possibility of reducing such errors when the fluctuations are considered. The possibility of optimizing the angular measurements of air objects in digital radars with PAA is shown, which consists in taking into account the fluctuations of the phase front of the received signal in the algorithm of discrete (fast) Fourier transform, which is widely used to provide spatial measurements in modern digital radar stations. The results of previous studies were generalized, which makes it possible to evaluate the possibility of increasing the accuracy of angular measurements of air objects during multichannel reception of a radar signal in difficult conditions of radar operation.

Author(s):  
Георгий Борисович Гуров ◽  
Валерий Юрьевич Поздышев ◽  
Александр Васильевич Тимошенко ◽  
Ольга Эдуардовна Разинькова

Работа посвящена построению процедуры идентификации маневрирующих объектов с использованием критерия идеального наблюдателя и фильтрации параметров трасс при сопровождении средствами мониторинга в интересах структурносистемного контроля воздушного пространства. Для минимизации среднеквадратических ошибок оценок координат и скоростей движения объектов разработаны алгоритмы экстраполяции параметров траекторий путем задания корректирующего шумового ускорения и замены результатов фильтрации оценок координат на измеренные значения при распознавании маневра. Обоснованы параметры фильтрации с шумовым ускорением в зависимости от точности измерений пространственных характеристик и идентификации при группировании однотипных признаков с наибольшими значениями условных вероятностей ситуаций отождествления объектов Purpose. This work addresses construction of the procedure for identifying maneuvering air objects in the process of tracking their routes. Monitoring tools during structural and system air space control are employed. The study is aimed to establish the abilities of correct identification of objects and false alarm at various standard errors of measurements of angular coordinates and to determine ways to increase efficiency of identifications performed due to selection of filtering options during trace tracking. Methodology. Identification of objects was performed according to the ideal observer criterion by comparing estimates of angular coordinates of objects subjected to linear filtering with corrective noise acceleration. In order to minimize root-mean-square errors of coordinates and motion velocity estimates of objects, route parameter extrapolation algorithms are obtained by setting correcting noise acceleration and replacing the results of filtering coordinate estimates with measured values during manoeuvre recognition. Due to a priori uncertainty of route parameters, target tracking was initially performed using recurring linear filtering while maintaining the priority of straight uniform movement. The recognition of the maneuver was carried out as a result of exceeding the difference between the measured and filtered values of the target coordinates of the threshold value. Findings. Filtering parameters with noise acceleration are justified depending on the accuracy of measurements of spatial characteristics and identification when grouping identification features with the highest values of conditional probabilities of situations for the objects under identification. As a result of replacing filtered parameters of alignments containing areas with rotations of 10 and 20, measured values for standard bearing errors (1 ... 2), the maximum error in determining directions for objects reaches 0.8 and 0.9, respectively. When replacing the estimates of the parameters of the alignments obtained using a recurring linear filter without taking into account noise acceleration, the coordinate values measured at the bearing error (0 . 5 ... 2), the errors of the filtered bearing of the targets at the angles of rotation of 10are (0 . 2 ... 1). When maneuvering objects with turns by 20, the largest value of the standard bearing error increases to 1.2. By increasing the accuracy of the diaper from 2 to 0.5, the probability of correct identification of objects in monitoring tools performing noise correction acceleration filtering increases by about 3 times and reaches a value of 0.9. As a result of replacing the estimates of the parameters of the alignments filtered taking into account the corrective noise acceleration with the results of measurements, the probability of correct identification of objects with standard bearing errors of not more than 0.5decreases from 0.9 to 0.85. Originality/value. The identification of maneuvering air objects is performed using filtering of route parameters calculated with the help of the ideal observer criterion. For the most efficient identification, the identification features belonging to the same object must be established according to the highest conditional probability of the identification situation. To minimize errors in estimation of the angular coordinates of objects, a procedure for filtering motion parameters with corrective noise acceleration is implemented


2020 ◽  
Author(s):  
Kensuke Kimura ◽  
Daisuke Yasutake ◽  
Takahiro Oki ◽  
Koichiro Yoshida ◽  
Masaharu Kitano

Abstract Background and Aims Most perennial plants memorize cold stress for a certain period and retrieve the memories for cold acclimation and deacclimation, which leads to seasonal changes in cold-hardiness. Therefore, a model for evaluating cold stress memories is required for predicting cold-hardiness and for future frost risk assessments under warming climates. In this study we develop a new dynamic model of cold-hardiness by introducing a function imitating past temperature memory in the processes of cold acclimation and deacclimation. Methods We formulated the past temperature memory for plants using thermal time weighted by a forgetting function, and thereby proposed a dynamic model of cold-hardiness. We used the buds of tea plants (Camellia sinensis) from two cultivars, ‘Yabukita’ and ‘Yutakamidori’, to calibrate and validate this model based on 10 years of observed cold-hardiness data. Key Results The model captured more than 90 % of the observed variation in cold-hardiness and predicted accurate values for both cultivars, with root mean square errors of ~1.0 °C. The optimized forgetting function indicated that the tea buds memorized both short-term (recent days) and long-term (previous months) temperatures. The memories can drive short-term processes such as increasing/decreasing the content of carbohydrates, proteins and antioxidants in the buds, as well as long-term processes such as determining the bud phenological stage, both of which vary with cold-hardiness. Conclusions The use of a forgetting function is an effective means of understanding temperature memories in plants and will aid in developing reliable predictions of cold-hardiness for various plant species under global climate warming.


Geophysics ◽  
1993 ◽  
Vol 58 (7) ◽  
pp. 997-1001 ◽  
Author(s):  
B. L. N. Kennett

For marine seismic sources quite efficient conversion of P‐waves to S‐waves can occur at hard seafloors, e.g., carbonate horizons in tropical waters. The S‐waves are reflected back from structures at depth and are reconverted to P‐waves in the water before detection by the receiver array. Such PSSP reflections can carry useful information on the structure beneath the sea bed but are most significant at large offsets and so are not easily stacked with a conventional normal moveout (NMO) procedure based on a hyperbolic time trajectory. A two‐layer stacking procedure that separates the water layer from the region below the seafloor provides a very effective means of extracting the PSSP arrivals, but also works well for P‐waves. There is no direct analytic form for the stacking trajectories but they can be calculated quite efficiently numerically. A further advantage is that the stacking velocity for S‐waves in the lower layer can be interpreted directly in terms of S‐wave propagation, so that S‐wave interval velocities can be found. Stacking procedures based on such simple physical models are likely to be useful in other cases where attention needs to be focused on a particular aspect of the wavefield.


2018 ◽  
Vol 28 (4) ◽  
pp. 28-34 ◽  
Author(s):  
A. O. Podkopaev ◽  
M. A. Stepanov ◽  
S. V. Tyrykin

The paper considers methods for modeling fluctuations of the phase front of an electromagnetic wave reflected from a radar object (reflections) using models that emit statistically related signals. Previously, such models were considered only in relation to objects distributed over a single angular coordinate. A two-dimensional geometric model, emitting statistically related signals, was proposed for replacement of reflections from radar objects distributed over two angular coordinates. The emitters of the model are located at the vertices of the square. Expressions are obtained for determining the characteristics of signals supplied to the emitters of such model, at which the model provides the required parameters of the probability distribution density of the angular noise of the distributed object. Within the framework of the model under study, it is proved that it is possible to control the parameters of the probability density distribution of angular noise along two coordinate axes independently. The equivalence of the four-point partially coherent model and the five-point incoherent in terms of providing the probability characteristics of the angular noise is shown, and the limits of this equivalence are also determined. The proven equivalence of models allows developing an apparatus for the synthesis of spectral-correlation characteristics.


Author(s):  
I. E. Makushkin ◽  
A. M. Shemarin ◽  
Yu. Yu. Vitsukaev ◽  
D. M. Tyurin

The previously presented method for measuring and calculating the components of boresight angle errors (BAE) in the “antenna – radioparent radome (RPR)” system in the two-dimensional angular scanning area of the antenna with electronic beam control, which includes a phased-array antenna (PAA), was tested in relation to a system with a drop-shaped radome. Measurements were carried out using an antenna measuring collimator complex (“compact polygon”) with a complex drop-shaped RPR and PAA installed thereunder. To create a BAE matrix on the surface of the RPR, measurements and subsequent calculations were performed at different “roll” angles of the antenna-radome system and different deflection angles of the PAA beam in “oblique planes”. The BAE measurements carried out in several RPR surface sections by the proposed method, show a good reproducibility and correlate well with the results of BAE measurements carried out using the same sections by the conventional difference method, where the BAE component is calculated as the difference between the angular coordinates of the minima of the corresponding PAA tracking pattern (TP), before and after the RPR installation.


Author(s):  
Klaus Baur ◽  
Marcel Mayer ◽  
Steffen Lutz ◽  
Thomas Walter

An antenna concept for direction of arrival estimation in azimuth and elevation is proposed for 77 GHz automotive radar sensors. This concept uses the amplitude information of the radar signal for the azimuth angle and the phase information for the elevation angle. The antenna consists of a combination of a series-fed-array structure with a cylindrical dielectric lens. This concept is implemented into a radar sensor based on SiGe MMICs for validation. A two- and a four-beam configuration are presented and discussed with respect to angular accuracy and ambiguities.


Author(s):  
Sergii Okocha ◽  
Andrew Petrenko

A new approach is proposed to obtain a generalized model of distribu­ -ted digital fiber-optic measuring systems of interferometric type using multichannel reception of signals of a fiber-optic inter-mode interferometer to improve the accuracy of measurements. On the basis of this approach, generalized equations for the con-version of fiber-to-digital converters of the geometric coordinates of the points of the measured object are obtained. The equations combine all the private mathema­ ti­ cal models of energy information processes. The approach is based on the representa-tion of the "coordinate of point (move) — code" in the form of an equation of perfect digital-to-analog source code conversion, the processes of which change bit codes are given in the form of logical functions from the input move and points of real multidimensional spatial parameters. The fiber optic line is used in bidirectional optical sig-nal mode in conjunction with the code element element. In this function, the supply of radiation from the measuring units to the points of reading information, the control ele­ -ment, transmitters of modulated radiation are combined in a single fiber. The spatial separation of optical streams is carried out in a block of bidirectional optical communication devices, which is a set of fiber-optic Y-splitters. For multichannel reception, the principle of making a decision on registration of influence on the interferometer is in-troduced: if the module of the output signal exceeds the set level, the signal is fixed. Changes in the measuring signal from external conditions are determined by changes in the parameters of the fiber, the processes of interaction of modes and double re-fraction. Changes in the measurement signal are presented as random variables. Using the central limit theorem for a large number of double sums, the values of the signals at a particular point in time are described by independent random variables, with a normal distribution law and a variance. The beneficial effect is considered regu-lar, and at the time of measurement it is represented by a centered Gaussian random variable with variance. The useful signal component is a Gaussian random variable with standard deviation.


Author(s):  
D.A. Semenov ◽  

The principles of radar sounding of lunar soil are revealed. The characteristics of the receiving-transmitting active phased antenna array and the possibility of its use in the transmission/reception of the probing radar signal in the study of lunar soil in the active mode from the flight scientific module are analyzed.


Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Jihua Zhang ◽  
Yun Dong ◽  
Yadong Chen ◽  
Huasheng Sun ◽  
Jingke Wu ◽  
...  

When the mountain tunnel projects passing through the complex formation with coal, it happened along with disaster accidents such as gas outburst, gas combustion, and gas explosion. These disasters should seriously threaten the safety and life of the construction personnel and affect the normal operation of the tunnel construction. Ventilation is the most effective means to control gas, fire, dust, heat, and other disasters. To study the effects of different ventilation modes in highway gas tunnels, Fluent software was used to simulate forced ventilation, exhaust ventilation, and mixed ventilation in a high gas tunnel of a highway in Hunan. The distribution law of the airflow velocity and gas concentration of these three ventilation modes were obtained to determine the optimal ventilation system. It was shown that vortex zones of different ranges formed in the tunnel for all three ventilation modes, and the gas concentration was higher in the vortex zone than in other regions. Mixed ventilation of them is superior to the other two modes, showing the best ventilation effect with regard to airflow velocity and gas concentration.


2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Wen-Qin Wang ◽  
Huaizong Shao ◽  
Jingye Cai

This paper proposes a range-angle-dependent beamforming for frequency diverse array (FDA) antenna systems. Unlike conventional phased-array antenna, the FDA antenna employs a small amount of frequency increment compared to the carrier frequency across the array elements. The use of frequency increment generates an antenna pattern that is a function of range, time and angle. The range-angle-dependent beamforming allows the FDA antenna to transmit energy over a desired range or angle. This provides a potential to suppress range-dependent clutter and interference which is not accessible for conventional phased-array systems. In this paper, a FDA radar signal model is formed and the range-angle-dependent beamforming performance is examined by analyzing the transmit/receive beampatterns and the output signal-to-interference-plus-noise ratio (SINR) performance. Extensive simulation examples and results are provided.


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