A Target Recognition Method Based on Non-Linear Polarization Transformation

Abstract

This paper proposed a target recognition method to distinguish ships from chaff by polarization information for the fully polarized dual-channel radars with low resolution. The method expands the original single polarization radar system to dual polarization radar system with both left and right circular polarizations by receiving and processing the full polarization information of radar echoes. It recognizes the target by taking advantage of the difference of the left and right circular depolarization characteristic parameters of the target and chaff in radar echoes.The recognition rate were improved in results by enlarging the difference between the cross-polarization component and co-polarization component of the radar echoes involving target and chaff employing non-linear polarization transformation. In the end, the recognition results were proved to be more desirable by processing information in polarization domain than in time and frequency domain.Chaff is constantly used in passive electronic countermeasure, and it is also one of the cheapest and most effective means in disturbing missiles or other aircrafts. It is disturbed, puzzled and tempted missiles or other aircrafts by the interference cloud made of mass randomly distributed chaff which length is half wavelength. According to the working principle of radar tracking target, the strong reflection of chaff cloud and the uneven distribution characteristics of the sparse cloud, it is difficult to distinguish ships from chaff in time and frequency domain. At the present, many articles describe the method to distinguish chaff cloud and targets by their differences in polarization characteristics, but due to the indistinctive difference, all the recognition results are not desirable enough. For this, this paper proposed a method of non-linear polarization transformation to enlarge the difference, which achieved a far more satisfactory effect than that in time and frequency domain.The deduction to be listed below is adaptive to dual-polarization radars with low resolution that transmits left and right circular polarization wave in turn and receives both right and left circular polarization wave with dual channels at the same time. * rNL NL r E M E =(1) rNL E is the polarized echo matrix after non-linear transformation, r E is the normalized receive polarization echo matrix, 1-4244-1035-5/07/$25.00 .2007 IEEE. 157

Jamming recognition method based on the polarisation scattering characteristics of chaff clouds

“…Many methods have been proposed to make such a distinction. These mainly include the Doppler behaviour of the chaff [26, 27], time‐domain correlation [28, 29], time‐frequency analysis of the radar echo [30], and polarisation discrimination [31–36], which seems to be the most promising methods [10]. Chaff jamming recognition based on the Doppler behaviour of the chaff is a simple but effective method, which can be divided roughly into two categories: Doppler filtering [26] and anti‐chaff jamming method based on the effect of spectral expansion [27].…”

“…the millimetre wave synthetic aperture radar (MMV‐SAR) seeker of European Aeronautic Defense and Space Company (EADS) [38], and the ground‐based radar for the national missile defense system (NMD‐GBR) in the USA [39] etc.]. As a result, applying the polarisation characteristics of chaff to jamming recognition has attracted the interest of researchers [31–36]. Since the warship is mainly dominated by dihedral scattering, it is reasonable to assume that the co‐polarised component of echoes of the warship is much stronger than the cross‐polarised component (∼12 dB) [25].…”

“…Afterwards, to further enlarge this ratio of ship and chaff clouds, a non‐linear polarisation transformation method is adopted by Shao et al . [32] and Li et al . [33].…”

Jamming recognition method based on the full polarisation scattering matrix of chaff clouds

“…The polarisation characteristics of chaff cloud are key features for chaff-jamming recognition [11 -17]. Polarisation characteristics of chaff cloud have been studied via the average RCS of chaff elements uniformly distributed in angle within the wave's polarisation plane [11], bistatic polarisation RCS of chaff cloud [12 -14], statistical properties of the polarisation backscattered field of chaff cloud [15,16] and non-linear polarisation transformation of the polarisation scattering matrix [17].…”

Chaff Jamming Recognition for Anti-Vessel End-Guidance Radars

“…Polarization-domain methods make use of the difference of cross-polarization characteristic between the target's echo and the chaff echo for recognition [2]. A complex full-polarization radar system is essential; as a result, it is difficult to use polarization-domain methods for end-guidance radars.…”