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

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The identification of model damping is a key for response analysis. A method is presented for updating damping of the computational model of substructure based on frequency response experiment. The proposed method directly identifies mass, stiffness and damping matrices by using the substructure error coefficient and frequency response experiment, then computational model damping is updated, finally the effectiveness of the method with simulated data gauging is studied in this paper.

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