A.V. Bulgakov – Post-graduate Student, Department «Radio Engineering», Voronezh State Technical University; Engineer, Analytics department, JSC «IRKOS» (Moscow)
I.B. Kryzhko – Ph.D.(Eng.), Senior Research Scientist, Research Sector of JSC «IRKOS» (Moscow); Associate Professor, Voronezh State Technical University
D.S. Radchenko – Post-graduate Student, Department «Radio Engineering», Voronezh State Technical University; Head of Sector of Software Testing, JSC «IRKOS» (Moscow)
A.B. Tokarev – Dr.Sc.(Eng.), Associate Professor, Professor, Department «Radio Engineering», Voronezh State Technical University; Head, Research Sector of JSC «IRKOS» (Moscow)
Effective use of the radio frequency spectrum requires careful monitoring of the actual radio placement and real frequency occupancy. Given the increasing prevalence of short-range communication systems and means, the radio environment analysis should be carried out by geographically distributed means of control, since even in the control points separated by several kilometers the radio environment may differ significantly. The active re-use of radio frequencies means that the detection in a frequency band of high-power radio emis-sions does not guarantee the absence in this band of other communication channels characterized by lower-power signals. Thus, the search for processing algorithms that allow the detection of weak signals against the background of powerful interference is relevant. Signal detection methods used in radio monitoring systems can be divided into two classes at least. In the presence of a priori informa-tion about the «fine structure» of the detected oscillations, correlation processing is an effective method of detection. For signals of un-known structure, the main method of detection is the energy method, but this method only allows us to establish that there is an energy burst in some frequency band. The energy method does not involve the separation of this burst into separate components and the detec-tion of cases of weak signals observation.
When conducting radio monitoring in open areas, the use of directional antennas can provide spatial separation of signals. In urban con-ditions, the observation of energy bursts from several directions does not guarantee the presence of several sources, but can be gener-ated by reflections of the same signal. Under these conditions, more promising are compensation algorithms for processing data col-lected by two-channel complexes of radio monitoring. The aim of the research was the development of algorithm for detecting weak sig-nals observed against a background of powerful interference, which has a wider range. Detection of weak signals is based on the algo-rithms of compensation of powerful interference, a sample of which is formed in a separate «reference» reception channel using an an-tenna with a narrow antenna diagram. The analyzed method of compensation of powerful interference is operable: 1) in the absence of a priori data on the structure of powerful interference; 2) during the panoramic radio environment analysis in a wide frequency bands; 3) when using radio monitoring systems equipped with antennas with an arbitrary way of controlling the direction of antenna diagram. Al-most all dual channel radio monitoring systems guarantee the possibility of synchronous data acquisition from the reference channel pro-viding a sample of interference, and from the signal channel receiving both powerful interference and the target signal, and their high operation speed allows you to quickly obtain a large amount of data necessary for the correct operation of the compensation algorithm. The compensation mechanism itself is based on the element-by-element data processing in the frequency domain, does not require large resources and can be used both for small and large width of the processed frequency ranges.
The possibility to detect weak signals at signal-to-noise ratios up to minus 10−15 dB has been confirmed during the full-scale experiment. However, the proposed method of noise compensation is not designed for the case of the presence of two or more indepen-dent interference sources in the analyzed band; the quality of noise compensation in the latter case may be unsatisfactory.
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