Radioelectronics and Communications Systems最新文献

Abstract

Small-dimension unmanned aerial vehicles (SUAV) as objects of radar surveillance feature extremely small values of the effective radar cross section and the capability to carry out intense maneuvers and to hover staying still in space. A promising direction of increasing the SUAV detection range by radar is the reduction of detection threshold that results in a significant rise of false alarm probability and is accompanied by the emergence of a substantial number of false pips. For enhancing the SUAV tracking efficiency in the presence of false pips, it has been proposed to use decisive statistics (amplitude information) from the output of optimal receiver of primary signal processing. An adaptive algorithm was developed for the radar tracking of maneuverable SUAV with probabilistic identification of data using the coordinate and amplitude characteristics in the rectangular coordinate system. Accuracy characteristics of extrapolation of SUAV movement parameters and the probability of detecting various types of its motion were obtained using statistical simulation. Probabilities of mistracking and the average time of SUAV trajectory tracking were calculated, and compared with the results of using a well-known algorithm.

Abstract

This article presents results of electromagnetic (EM) simulation and experimental research of an original tapered slot antenna with modified topology and double-sided metallization. A comparison of this antenna with classical and antipodal topology is performed. Advantages and disadvantages of each of them are described. It is shown that due to the mirror symmetry planes in E- and H-planes, the proposed antenna has the highest crosspolar isolation and demonstrates electrodynamic characteristics acceptable for practice in the frequency range 0.5–6.6 GHz. Transition from an asymmetric 50-Ω coaxial line to a symmetric 100-Ω slotted line is made with the help of a balun placed in the same plane as the antenna. The latter simplifies the manufacturing process and radically reduces the longitudinal dimensions of the antenna. The research results indicate on potential application possibilities of the developed tapered slot antenna in various areas of wireless technologies.

Abstract

The Dowell and Ferreira calculation methods for the loss resistance of choke windings are analyzed in this paper. We determine that the neglect of the winding geometry influence is the cause of their error, because the problem is solved on a plane. The influence of winding geometrical parameters on current distribution in conductors is investigated for verification. The influence of single layer winding geometry on loss resistance for conductors of different diameters is considered. It is determined that the influence of winding geometry on the loss resistance is significant (up to 40%), and it increases with increasing conductor diameter and frequency, and decreasing coil diameter. There is non-uniformity in current distribution of coiled into a ring conductor caused by proximity effect. The influence of inter-winding distance for a single layer winding on its loss resistance is studied. The influence of interturn proximity effect is significant and increases with decreasing inter-winding distance. The reason for discrepancy with known methods is the non-uniformity of current distribution in the outer and inner turns. The peculiarities of current distribution in square cross-section conductors and equivalent in area cylindrical conductors presented as straight single conductors, single turns, and single layer windings are considered. The influence of the conductor shape on current distribution and its density are determined.

Abstract

The third part of a series of papers deals with the diagnostics and treatment of patients, both military personnel and civilians, who have suffered traumatic brain injury (TBI) and barotrauma due to combat concussion (CC) with the development of post trauma stress disorder (PTSD). The main method for diagnosing neuro-cognitive changes in such patients is neuropsychological testing (NPT). However, based on different types of questionnaires, the NPT results can have significant inaccuracies associated not only with the subjective opinion of doctor, but also with inadequacy, and, sometimes, with deliberate actions of patients. This leads to the need of developing new objective diagnostic techniques that would confirm and refine the NPT results.

The current paper presents the development of the methodology for assessing the neuropsychological state of servicemen with CC-caused mild TBI based on single-photon emission computed tomography (SPECT) data, in particular, based on the analysis of volumetric cerebral blood flow (CBF) and perfusion intrahemispheric symmetry (IHS) in segments of the brain.

The data of 31 patients with moderate TBI due to CC were analyzed. The consequences of TBI should be considered remote, since at the time of their comprehensive examination from 6 to 12 months passed after the contusion. NPT was used to assess the degree of vegetative disorders according to Wayne of psycho-emotional sphere, the severity of symptoms of traumatic brain damage based on the K. Cicerone questionnaire, and the severity of PTSD based on PCL-military tests. SPECT investigation was carried out using 99mTc-hexamethyl-propylene-amine-oxime (^99mTc-HMPAO). The main quantitative criteria for the analysis of SPECT images were volumetric cerebral blood flow (CBF) and intrahemispheric symmetry (IHS) of perfusion in brain segments. Based on the comparison of CBF and IHS in segments of the brain with the NPT data, the highly correlated relationships were obtained that amounted from 0.82 to 0.90. At the same time, for each of NPT tests, 3–4 brain segments could be singled out, where CBF and IHS to the fullest extent reflect the neuro-cognitive state of the patient. It has been shown for the first time that on the basis of objective SPECT data with ^99mTc-HMPAO it is possible to quantify the patient’s neuro-cognitive state. The research results can be recommended for a wider use in departments of radionuclide diagnostics when examining the military personnel with TBI in the aftermath of CC.