V.A. Aladinskiy – Ph. D. (Eng.), Professor, 

LTD «STC» (St. Petersburg)

E-mail: awa2810@yandex.ru 

V.F. Korotkov – Dr.Sc. (Eng.), Senior Research Scientist, Chief Civil Engineer of Projects,  LTD «STС» (St. Petersburg)

E-mail: diofant2912@mail.ru

Analysis of the known formulas for determining the range in between the source of emition (SE) and the receiver in radio control systems showed that they do not take into account the loss of energy during the propagation of radio waves (PRW). The cases of PRW under conditions of standard, superrefraction, subrefraction and trapping are considered. The existing algorithm for calculating the detection range in between SE and receiver does not take into account the presence in the troposphere of inversion layers that form a tropospheric ducting (TD) above the sea surface.

Tropospheric ducting arises due to the effect of trapping, in which the vertical profile of the refractive index N(h) has an area (trapping layer) characterized by magnitude dN/dh>0. Based on the well-known concept of a modified high-profile (M-profile), such types of TD as surface ducts, surfacebased ducts, elevated ducts and evaporation ducts, as well as the values of their parameters: height

hB, thickness Δh (difference between the upper and lower boundaries of TD) and the magnitude 

M-inversion ΔM=M(h0)–M(hB), where h0 the initial height at which dM/dh<0. For these types of TD, graphs of the dependence of the energy loss L on the range D are given.

An algorithm is proposed for determining the detection range in between SE and receiver for marine passive radar in the presence of one of the types of TD above the sea. The initial data in the algorithm are the values of the parameters of the RS, the passive radar and the atmosphere characteristics on the sea radio paths. The algorithm provides for the following steps: modeling of the path profile for the given values of the maximum distance Dmax of detection of RS and Hmax≥hB; calculation of the electromagnetic field strength U(x,z); determination of the total energy loss of radio emission LΣ; calculation of the value of the PR power of the signal RS at the input of the radio receiver (RR) passive radar; check the condition PR – SR > 10 dB, where SR is the sensitivity of the RR. If this condition is not fulfilled, the value of Dmax decreases and all calculations are repeated again. The results obtained by computer simulation on a computer using this algorithm allow us to conclude that the use of characteristics of refractive electromagnetic field  outside the radio horizon contributes to an increase in the distance up to 500 km in between SE and receiver over the sea when  conducting passive location.

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