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Two-Channel Search for Electromagnetic Emission of Technical Apparatus on the Background of External Interference


A.A. Bylinkin

The article covers the topical issues in the field of information protection – search and analysis of electromagnetic emission (EME) of operational technology (household, computer, and special) against a background of external noise. As a source of external noise can perform: broadcasting and television stations, distant from the object, mobile and stationary means of cellular communications and etc. In this case, frequency bands of EME of technology and external noise can coincide and the power of EME can be less than the power of external noise. Stated factors substantially complicate the task of revelation of EME in technology. In case of absence of prior information about parameters of revealed EME and external noise as a solution of the task of revelation, comparison method of forms of electromagnetic spectrum, accepted in two space-straddling spots with the help of equipment, which has two synchronously working reception channels, can be suggested. The solution of this task is based on the fact, that forms of electromagnetic spectra of external noise in different spots of the space can have high strength of association, and forms of spectra of revealed EME and external noise have some distinctions. For the purpose of revelation of EME in technology the choice of spots in the space for installation of receiving antennas is made. The first spot (main) is situated near supposed place of installation of EME source, the second one (supporting) – is moved away from the first spot on a rather big distance. With a glance of technical features of used equipment, specificity of spot’s choice in the space for reception of electromagnetic modes and a series of mathematical supposals, algorithm of revelation can be made in following way. If in reception channels of equipment similar spectra of electromagnetic modes are received, the decision about absence of EME of technology is taken. But if in forms of spectra some distinctions are revealed, than the decision about presence of EME of technology is taken. The level of similarity and distinction in forms of spectra is determined in general case of decisive function, on the basis of which algorithm of revelation is made. Design of two-channel algorithm of EME revelation of technology in the frequency band, which is occupied with external noise, is based on the application of the theory of Gaussian random variable and generic method of maximum likelihood. Analysis of effectiveness of obtained decision was conducted in «MATLAB» medium. Consequently, it was shown the raising of effectiveness of the algorithm during declination of similarity in forms of EME spectra of technology and external noise. The possibility of raising of probability in right EME revelation at the cost of raising of frequency sample number in analyzable frequency band and raising of power of external noise in the second channel of the equipment is ob-served. In conclusion directions of further researches on the topic of the article are determined.
June 24, 2020
May 29, 2020

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