V. P. Kortnev – Ph.D. (Eng.), Senior Research Scientist
D. V. Mordasov – Junior Research Scientist, Laboratory of Radio Photon Systems, JSC «CRET» (Moscow)
Currently, several methods of detection of directional patterns (DP) of phased antenna arrays (PAA) are known in the literature and radio detection and ranging practice. In this paper, there are estimated distortions of the DP shape, built with the help of mathematical model – an equation derived while using a broadband signal (BBS). The mathematical model of the broadband signal was obtained with the help of discrete Fourier transformation of instantaneous spectrum of multi-frequency signal with a predetermined pulse repetition frequency and predetermined relative spectral band within the required frequency range. To ensure the adequacy of the mathematical model of the directional pattern in the presence of a broadband signal, derivation of the equation of directional pattern of phased antenna array in the presence of monochromatic signal is represented. The applied methodology has allowed obtaining the ratio that is completely identical to the formula known in the literature. Derivation of ratio for the directional pattern with use of a broadband signal has been carried out in accordance with the foregoing methodology. As the estimation criteria, there are admitted deviations of the DP parameters during the process of receiving or transmitting the BBS (the DP width, side lobes level (SLL), the presence and the level of grating lobes) from the same parameters of the DP, built with the use of monochromatic signal and the equation known in the literature. The tests of the mathematical model of the PAA DP at the signal relative spectral band coming to 20% and more and “compression” ratio coming to 10 has shown that the widths of the compressed DP and SLL do not differ from the same parameters in the presence of monochromatic signal. The differences are observed in the fact that the structure of side lobes in the presence of a broadband signal does not have a “zero” level, and during deviation of the beam for angle of +60 degrees from the normal in the direction of -60 degrees there grating lobe appears at the level of -41 dB. Apart from that, the grating lobes after compression of the directional pattern (in the presence of broadband signal) even before suppression are lower that the main one in terms of the level as opposed to the case of monochromatic signal. Basing on the obtained results, this research paper concludes that the signal bandwidth (within the limits of practical application) does not reduce the effectiveness of the algorithmic “compression” of directional patterns.
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