PECULIARITIES OF MULTIFREQUENCY SIGNALS FEATURES AND THEIR USING IN RADARS FOR DETECTING OF LOW-ALTITUDE TARGETS OVER SEA
DOI:
https://doi.org/10.26906/SUNZ.2018.3.050Keywords:
multifrequency signals, serial pulse multifrequency signals, detection radar, low altitude target, coherence of signalsAbstract
The subject matter of the article is multifrequency radars for detecting of low-altitude targets over sea. The goal is to increase the efficiency of multifrequency radars for detecting of low-altitude targets over sea. The tasks to be solved are: analyzing multifrequency signals in the sequential formation of their components with the use of analytical formulas for a random multifrequency signal; mathematical modeling of two-dimensional correlation functions for different phase-frequency codes of the multifrequency signal; to develop recommendations for the use of low-altitude targets in the radar. The methods used are: methods of statistical radio engineering, probability theory and mathematical statistics. The following results were obtained: time-frequency diagram, amplitude-frequency spectrum, two-dimensional correlation function of uncertainty, as well as normalized autocorrelation and frequency-correlation functions for different phase frequency codes of the multifrequency signal are obtained. The coherence band, the main lobe duration and the side lobe level of the autocorrelation of the impulse multifrequency signals with components without internal modulation and pulsed multifrequency signals with linearly frequency modulated components with different codes in frequency and phase, as well as different widths of the discrete spectrum and their different frequency spacing are analyzed. Conclusions. The comparative analysis of the main types of serial multifrequency signals allows to formulate recommendations regarding their application in the radar for detecting low-altitude targets in various conditions of interference situation is conducted. For example, it is more expedient to use serial multifrequency signals with a continuous amplitude-frequency spectrum to improve the detection characteristics of low-altitude targets in the radar channel over the sea in fluctuation noise. The envelope signals and those ones with a not continuous amplitudefrequency spectrum are more expedient to use under conditions of deliberate time-varying and frequency-non-uniform interference. The serial multifrequency signals with a rectangular envelope and the amplitude-frequency spectrum, which consists of the components of the amplitude-frequency spectrum that intersect, are more suitable for improving the detection of lowaltitude targets over the sea in a radar channel with modulating interference.Downloads
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