Zhurnal Radioelektroniki - Journal of Radio Electronics. ISSN 1689-1719. 2020. No. 4
Full text in Russian (pdf)
Study of the near radiation zone field of ferrite magnetic antenna
I. B. Shirokov, M. A. Durmanov, I. V. Skorik
Sevastopol State University, Instate of Radioelectronics and Information Security, Universitetskaya, 33, Sevastopol, 299053, Russia
The paper is received on March 24, 2020
Abstract. The common characteristics of the long-wave range radio signals and their high penetrating ability at propagation through the rock mass are provided, which stipulates their use for underground radio communications. The problem statement is given, which shows that at a distance from the source less than λ/2π, where λ is the wavelength of the signal emitted (near radiation zone), the electromagnetic field can be considered as quasistatic and the field calculation can be conducted as for stationary fields. A system of two magnetic coils with ferrite cores is considered. The system generates an alternating magnetic field and further the field is received at the receiving point. The coaxial arrangement of coils is considered for theoretical research. The expression for EMF induction and the induction current dependence of the distance in coaxially placed coils is obtained. The expression shows that EMF induction decreases in inverse proportionality to the cube of the distance. The expression has all the parameters independent of the distance combined into a single proportionality coefficient characterizing the specific system. The obtained result shows the dependence of EMF induction and the induction current induced in the receiving circuit from the parameters of coils. The influence of a ferrite core on the magnetic field that is generated and received by coils with ferrite cores is considered and analyzed. However, the maximum current induced in the receiving coil is determined not only by the design and electrical parameters of the coils, but also by their relative placement. The experiment is dedicated to the study of the effect. Prototypes of the transmitting and receiving devices operating at a frequency of 128 kHz were used for the experiment. The receiving signal level dependence on the distance between the transmitting and receiving devices in the range from 5 to 60 meters with coaxial and parallel mutual positioning of the coils where the coils are at the same level in same plane was experimentally studied. The experimental results are compared with the theoretical dependence by plotting dependencies in single coordinate system and their close correlation is shown. The results of the studies are useful to solve problems such as search of people trapped under the rubble in the mines. Knowing the nature of the change in the field created by the beacon, the level of the received radio signal can determine the distance to the transmitter, and thus locate the search object that has the beacon.
Key words: near radiation zone, ferrite magnetic antenna, induction electromagnetic force, alternating magnetic field.
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Shirokov I.B., Durmanov M.A., Skorik I.V. Study of the near radiation zone field of ferrite magnetic antenna. Zhurnal Radioelektroniki - Journal of Radio Electronics. 2020. No. 4. Available at http://jre.cplire.ru/jre/apr20/6/text.pdf. DOI 10.30898/1684-1719.2020.4.6