К.Е. Mukhomor - Research Engineer, Department Radio Engineering Systems, Tomsk State University of Control Systems and Radioelectronics E-mail: mukhomorke@main.tusur.ru А.S. Anikin - Ph.D. (Eng.), Research Scientist, Department Radio Engineering Systems, Tomsk State University of Control Systems and Radioelectronics E-mail: rbk@sibmail.com N.А. Kolyadin - Research Scientist, Department Radio Engineering Systems, Tomsk State University of Control Systems and Radioelectronics E-mail: kolyadin.nik@bk.ru М.V. Krutikov - Head of Laboratory, Department Radio Engineering Systems, Tomsk State University of Control Systems and Radioelectronics E-mail: rwplab@tusur.ru

The introduction of new radio frequency bands for use in the forest requires preliminary studies. Modern trends is the increase in op-erating radio frequency. Also, there is a necessity for locating radio sources. The purpose article is to study the characteristics and properties of the pulse signals, which have passed a short forest track near surface. With the objective of evaluating the direction finding accuracy of radiation sources. The studies were conducted between September and October 2012 in the vicinity of the city of Tomsk. Measurements were obtained for three routes. Length of the route is from 130 to 400 meters. Trails differ in greenery density. radiation source was a portable radar, a pulse signal duration of 275 ns and a frequency of 9,2 GHz without intra-modulation, antenna gain 23 dB and a peak power of 10 kW. Reception and recording equipment consisted of an antenna system comprising two dipole antennas located at 45° to the horizontal and the two-channel receiver with quadrature receive channels. The antennas formed a direction finder with base length 20λ, recording equipment can record the quadrature components of the signal with a sampling frequency of 90 MHz. Recordered data obtained in a mode of mutual guidance IRI antenna and receiver systems. Registration time for a route №1 was 6 minutes for routes №2 and №3 18 minutes. In some implementations 20000 representing registration window 2,8 ms duration was recorded during this time on each of the tracks. When processing the data evaluated the following parameters and their characteristics: the average value of the signal amplitude in the channels M(U), it-s RMS σ(U); pulse duration at the threshold level detection algorithm τимп; change the duration of the received pulse Δτ with respect to the rating; the phase difference M(Δφ), it-s RMS σ (Δφ); bearing on the radiation source M(α), it-s RMS σ (α). Based on these results the following conclusions: lots of forests significantly affect the received signal. For closed trails changing the amplitude of the received signal reaches 30 dB; the sharp increase in RMS amplitude in the channels, for both indoor tracks, this value is comparable to the value of the amplitude of the received signal; appreciable «expansion» of the received pulse (30-70%) relative to the duration of the emitted pulse; the standard deviation of the phase difference evaluation on closed roads did not exceed the values in the 40°, which made the mistake of direction finding about 0,3 arcminutes.

 

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