Dai Dahai

Band Characteristics of SINR Polarization Filter

The band characteristics of the signal-to-interference-and-noise-ratio polarization filter to one signal in the presence of single noncoherent, purely polarized interference are investigated. The formulae of the filter band width on the polarization tracks and in the whole polarization region are presented. The quantitative description and the characteristic curves of the band scale are also given

Polarization target detection algorithm based on instantaneous Stokes sub-vector

Firstly, the statistics of random polarized waves instantaneous Stokes sub-vector is analyzed and its probability density function (PDF) is obtained. Secondly, the target detection problem is skillfully translated into the detection problem of three equivalent polarization signals. Thereby, a novel fusion detection algorithm is presented based on the difference statistical distribution of Stokes sub-vector between targets and clutters. Experimental results show that no matter the target is random polarization or invariable polarization, the algorithm is effective. Its performance can be comparative to that of the optimal polarization detector (OPD) and better than that of the polarization white filtering detector (PWF). Considering variable conditions of polarimetric measurements, it can be used more widely than the optimal polarization detector

Fully polarized radar target scattering center extraction

A new method for fully polarized radar target scattering center extraction is proposed using Coherent Polarization Geometrical Theory of Diffraction (CP-GTD) model. Unlike the traditional single fixed-polarization GTD method, the new method can overleap the step of scattering centers association and can estimate coherent scattering matrices of scattering centers accurately. It also provides a better performance and a reduced computation burden because the full-polarization information is used. The superiority of the CP-GTD is verified by experiment results based on simulated data. The method can also be easily extended for SAR/ISAR.

Spacial polarization characteristics of antenna

Based on interpreting the conception of antennas spacial polarization especially for instantaneous polarization detailedly, the description framework of spacial polarization characteristics for antenna is introduced in this paper. Some classical descriptors and instantaneous descriptors are given. On the basis of this, the spacial polarization characteristics of theoretical orthogonal dipole antenna and a practical jammer antenna is analyzed. The corresponding computer simulation is completed. The result indicates that antennas polarization characteristics often changes by rule in different radiation direction. The research in this paper also provide theoretical base and support for the application of the spacial polarization characteristics of antenna.

Developments and prospects of high-performance detection imaging and identification

High-performance detection imaging and identification is one of the frontier areas in modern information science. It has developed rapidly in recent years, and the urgent need for its applications has accelerated the development. In this paper, four key areas of high-performance imaging detection and identification, namely multi-dimensional microwave detection imaging, weak signal detection and recognition, multi-mode imaging theory and information reconstruction, and computational imaging theory and methods, are systematically expounded in the areas of concept and content, development status both at home and abroad, current popularity and difficulty, typical applications, and future developing trends. In addition, related scientific issues are discussed and summarized. Although the specific problems faced in each field differ from each other, some common and fundamental issues, which should be investigated, include the interaction mechanism between the imaging measures and the target, the acquisition mechanism of detection-imaging data, and target-feature extraction and reconstruction after detection imaging.

A super-resolving imaging algorithm of forward-looking SAR based on compressive sensing

As having the imaging ability of area in front of flight direction, forward-looking synthetic aperture radar (SAR) has become a hot topic in areas of SAR research. Nevertheless, the currently exploited imaging algorithms of forward-looking SAR suffer from poor azimuth resolution induced by limited azimuth aperture length. To address this challenge, we develop a super-resolving imaging algorithm for forward-looking SAR based on compressive sensing theory. Firstly, the spatial geometry and signal model of forward-looking SAR is analyzed. After that, the compressive sensing theory is introduced to improve azimuth resolution. Imaging simulations based on Ku-band image data from the MiniSAR system demonstrate the effectiveness of the proposed method.

Radar target recognition method based on physical-statistical model

A novel radar target recognition method based on physical-statistical model is proposed, which uses sequences of full-polarization high resolution radar range-profiles (HRRP). The HRRP of target is modeled as a Middletons Class A non-Gaussian distribution through a physical consideration. It is found that the model parameters describe the scattering physical characteristics of radar target and can be chosen as feature vector for radar target recognition. The Parzen window is adopted to estimate the probability distribution function of model parameter and the classifier is designed via Bayes theorem. The approach is applied to the classification of measured data. Numerical results have shown that the approach can extract the features which are not sensitive to target orientation and are effective to radar target recognition.

Optimal polarimetric interferometry coherence analysis in detection and location of moving target with SAR

This paper mainly deals with the problem of the optimal polarimetric interferometry coherence in detection and location of moving target with SAR. The coherence is closely related with the estimated accuracy of the interferometric phase between the residual images which are obtained from clutter cancellation. A novel method for improving the estimated accuracy of the interferometric phase is presented. Using the echo model of moving target, the procedure of clutter cancellation in frequency domain is derived. The optimal polarimetric interferometry processing for residual images is proposed with detailed analysis. Finally, the interferometric coherences of the residual images with different polarization are analyzed by simulation to validate the theory.

Performance analysis of adaptive polarization filters [radar anti-jamming]

In dynamic electromagnetic environments, a polarization estimator is usually utilized by an adaptive polarization filter to acquire the knowledge of the polarization of the interference field, then optimal polarization is calculated for the polarization filtering. In this sense, an adaptive polarization filter can be modeled as an open loop cascading system of a polarization estimator, an optimum polarization calculator and a polarization filter. Based on dual channel orthogonal polarization measurements, a theoretical performance analysis of the polarization estimator is derived. It is proved that the polarization estimation error obeys the Rayleigh distribution, approximately. Finally, by studying the transmission process of the estimation error in a polarization filter, a series of analytic formulae on the performances of adaptive polarization filters are derived, which statistically reveal the relationship between the filtering performance and the signal to noise ratio clearly.