Block principle of constructing and estimating the rcs reduction of nonabsorbing broadband 2 bit anisotropic digital meta-coatings.

The block principle of constructing of coding matrices for non-absorbing flat digital anisotropic meta-coatings (MC) used to reduce monostatic RCS of objects is considered. The essence of this principle consists in 2-bit coding of the tilt angles of the anisotropy axes of the MC modules so that four arbitrary adjacent modules of the MC form two pairs of antiphase modules. The use of the block principle in the development of a MC provides a reduction of monostatic RCSs on cross polarization due to cancellation of interference waves. The reduction of the monostatic RCS of a MC at matched polarization (co-RCS) is due to the twist-effect. Simultaneously with cancellation and twist-effect, diffuse wave scattering is implemented in the developed digital MCs. The proposed 2-bit anisotropic MCs make it possible to achieve a more effective reduction of monostatic co-RCS (in relation to the traditionally accepted level of minus 10 dB) in a wide frequency band, for different polarization planes of the incident wave. The impedance and full-wave models of the two main blocks of digital anisotropic MCs are developed. An asymptotic representation of the polarization scattering matrix is obtained for the impedance model of the MC block using the method of physical optics. The algorithm for calculating the frequency characteristics (FC) of monostatic co-RCS of impedance models of MC blocks is implemented in the Octave program. Full-wave models of MC blocks are built using the HFSS program. Layouts of two main MC blocks were made. Monostatic co-RCSs of the blocks are measured in the 7÷17.5 GHz frequency band for different polarizations of the incident wave. It is shown that the calculated and measured frequency characteristics of monostatic RCS of the models and layouts of blocks of 2-bit anisotropic MCs are in good agreement. The calculated and measured levels of monostatic RCS reduction of the main blocks are at least 12.5 - 13.5 dB at different co-polarizations in the band from 10.2 to 17.5 GHz and higher (based on the results of calculations).

DETECTION OF RADAR TARGETS ON THE BACKGROUND OF ACTIVE INTERFERENCE BY THE DETECTOR OF THE POLARIZATION MATTER OF THE SCATTERING

The article discusses the possibility of detecting radar targets moving under the cover of active noise masking interference, acting along the main lobe of the antenna system's radiation pattern, and also using self-covering noise. It is shown that in radar stations with full polarization sounding of the space and measurement of the polarization scattering matrix (PSM), it is possible to synthesize a decisive rule for target detection against active noise-free correlated interference. This synthesis is possible on the basis of the determinant of the polarization scattering matrix, the value of which has the properties of invariance to the form of the polarization scattering vector. The analysis of the determinant of the polarization scattering matrix in the conditions of measuring its elements against the background of active interference makes it possible to identify differences in the values of the determinant under conditions of presence and absence of a target in the volume of space allowed by the radar system. In this case, the value of the determinant becomes the main information feature. A distinctive feature of the detector is the invariance to the form of the polarization scattering vector. The detector synthesis is based on differences in the signals of the secondary and primary radiation, which appear at the output of the PSM meter, namely, on the properties of the determinant of the polarization matrix of the scattering of the object and the signal received from the source of active interference. The purpose of the article is to illustrate the differences in the properties of the polarization scattering matrix at the output of the PSM meter in the presence of active interference and / or a useful signal, as well as the possibilities of using the existing differences in the properties of PSM and their estimates in the presence of active interference for the synthesis of a radar detector.

Radar Target Characteristics Extraction using Polarization Scattering Matrix

<p>Now a day’s characterization of targets using radar is very important in Air Traffic Control, Defense, and Stealth etc. In order to know the characteristics of the target it is very essential to know the polarization properties of that particular target which depends upon scattering nature of the target. The polarization properties are important for radar target besides amplitude, phase and frequency. The polarization may be potentially used to improve target detection, anti-interference, and radar target recognition. Polarization properties of a target can be obtained using polarization scattering matrix (PSM). In this paper the polarization matrix of various geometrical shapes are derived. For radar target recognition (RTR), a method using properties of the polarization scattering matrix (PPSM) is presented in this paper. A dipole has been considered to calculate the polarization matrix and polarization properties. The properties of the polarization scattering matrix: the determinant, Trace of Power Scattering Matrix, Depolation, Eigen polarization angle and Module of Polarization Ellipticity are analyzed. These properties are analyzed for different orientation angles of the targets.</p>

Basics and first experiments demonstrating isolation improvements in the agile polarimetric FM-CW radar – PARSAX

The article describes the IRCTR PARSAX radar system, the S-band high-resolution Doppler polarimetric frequency modulated continuous wave (FM-CW) radar with dual-orthogonal sounding signals, which has the possibility to measure all elements of the radar target polarization scattering matrix simultaneously, in one sweep. The performance of such radar depends of the level of sounding signals orthogonality. In the main operational mode, the radar will be used for atmospheric remote sensing and polarimetric studies of ground-based targets. In such mode it will use a pair of synchronous linearly- frequency modulated (LFM) continuous signals with opposite frequency excursions of 50 MHz and duration of 1 ms. Such a combination of sounding signals has limited orthogonality even for huge BT-products, which produce cross-channel interferences. These interferences in case of radar scene with multiple pointed and distributed targets can completely degrade radar operational performance. In this article, we propose simple and effective technique to suppress interferences and to restore radar performance. The technique has been tested using simulation and has been implemented in multi-channel digital receiver of the PARSAX radar. The real radar measurements presented to illustrate effectiveness of cross-channel interferences suppression. The proposed technique can be useful not only for polarimetric radar design, but also in much wide radar applications, which use waveforms with high orthogonality.