S.P. Barinov - Dr. Sc. (Eng.), Senior Research Scientist, Corresponding Member of Russian Academy of Engineering, Deputy General Director, JSC «Kaluga Scientific Research Radio Engineering Institute» V.N. Grib - General Director JSC «Kaluga Scientific Research Radio Engineering Institute» Yu.I. Majewski - Dr. Sc. (Eng.), General Designer Electronic Warfare, Deputy General Director JSC «CRET»

One of practically important cases of functioning of a radar system comprised of several single-type spaced apart transceiving elements (a networking radar system) is detection of a jammer source (self-protection jamming) affected by correlated noise and deception jamming generated by other sources. However, the problem of synthesis and analysis of algorithms of optimal space-time signal processing by networking radar systems affected by several noise and deception jamming sources is not thoroughly covered in the known literature. The objective of this paper is to elaborate and estimate algorithms of optimal space-time signal processing by networking radar systems with discrete, continuous-discrete or continuous antenna aperture in presence of several correlated noise «self-masking» jamming, as well noise and simulation jamming generated by other sources. To achieve the objective three tasks were set up and solved in this paper: 1. Signal and jamming model development for receiving elements of the networking radar system. 2. Synthesis of algorithms of optimal space-time signal processing by networking radar system in the presence of several emitters of noise and deception jamming. 3. Parametric estimate of the influence of jamming source number on the quality of space-time signal processing. To solve the first task the networking radar system was considered as an assembly of interconnected spaced transceiving points. By means of space-time sampling calculus (strobe functions) applied under unified methodologic approach, models of a carrier signal, noise and deception jamming for radars with transceiving antennas with continuous, continuous-discrete or discrete antenna apertures as well as with continuous and pulse probing signals, were developed. The suggested models cover for specifics of different objects under observation including spatially concentrated and spatially extended, moving or stationary ones. In particular, for local spatially extended objects with applying scattering function a model that establishes the connection between fields of radiation and scattering on its surface and enables a wide range of models of elementary radar signals while surveying different types of objects, was validated. To solve the second task, synthesis of algorithms of optimal space-time signals processing affected by noise and deception jamming is carried out within the frame of multialternative detection problems. This enabled to develop algorithms for optimal detection of fluctuating space-time signal for reception in far-field and Fresnel region, and to show that several thresholds are formed in optimal (according to Neumann-Pearson criterion) multialternative space-time receiver-detector and false alarm stabilization is ensured for all alternative signals. For the model of a useful signal as a sum of target echo return and generated by it active noise jamming, algorithms of optimal space-time signals processing affected by narrow-band interference in radars with continuous-discrete apertures of receiving antennas were synthesized. It was shown that in this case the base portion of the reference signal ensures optimal signal processing in presence of active jamming (signals power is summed up), and compensating portion of the reference signal is «tuned» to the narrow-band noise jamming. The produced algorithm features removal of time and frequency offsets both in echo returns, and active noise jamming received and repeated by various system components, their gating and band-pass filtering, correlated processing in all kinds of paired combinations, multiplication by weight factors and summing the obtained signals for one and the same resolution cell. As a result of solving the third task relationships between SNR at the output of the radar system and the number of correlated jamming were obtained, that helped to establish the following: Increase in number of jamming sources results in reduction of «signal-to-noise» ratio, which gets more considerable, the less is cross-correlation of jamming; with 3−4 jamming sources and cross-correlation coefficient not higher than 0,5 the SNR is reduced by 4 - 4,5 times. Increase of cross-correlation coefficient of signal and jamming leads to considerable reduction in SNR; e.g., rise of cross-correlation coefficient of signal and jamming from 0,3 to 0,7 yields reduction in SNR down to 3,5 - 7 times. The gain at optimal processing in comparison to the matched one is sharply reduced with increase of jamming source number and with the number more than 4 it equals to 2 - 2,7 dB. It is shown that the essence of the effect of signal-noise ratio degradation at the output of the optimal processing system while the ratio of signal-jamming cross correlation increases along with the number of jamming sources consists in expansion in the number of «spurious» cross-correlation couplings between jamming generated by different sources as well as between jamming and the signal with the corresponding increase of noise component level remainder.

 

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