Wang Xue-song

Mathematic principles of interrupted-sampling repeater jamming （ISRJ）

Coherent jamming is one of the important trends in modern radar electronic warfare. High-speed sampling of wideband radio frequency (RF) signals and high isolation of two receive-transmit antennas are key technologies for the realization of coherent jamming. However, these technologies present significant challenges to engineering application. In this paper, a novel repeater jamming based on interrupted sampling technique is presented. For a jammer with a receive-transmit time-sharing antenna, a radar signal is sampled with a low rate by the jammer. Then, a train of false targets will be achieved after the jamming signal feed the matched filter of a pulse compression radar. For the case of the linear frequency modulated (LFM) pulse compression radars, mathematic principles of the interrupted-sampling repeater jamming is developed, and then the efficiency of the jamming is described and stated as expressions of key parameters which are also beneficial to the jamming design for other coherent radars.

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 property of scanning slot phased array

There are three typical definition of cross polarization in mechanical scanning antenna, and they are not completely proper for electronic scanning phased array antenna. We use wave-guide slot phased array antenna in this paper to study the changing of polarization property as beam scans in wide airspace. Simulation shows that the property of lobe and polarization changes not much in the case of small azimuth and elevation scanning angle. However, there is dramatic increase of cross polarization component in main lobe in the case of large scanning angle. We can use this characteristic to measure polarization property of target in phased array radar searching stage.

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

Joint Spectrum estimation of Polarization and Space

The Joint Spectrum of Polarization and Space is constructed for the first time, which can depict the EM signal more completely. Based on the polarization sensitive antenna array, the joint spectrum is defined and the analytic function of joint spectrum is presented by MUSIC method. The discrimination power of joint spectrum is discussed theoretically in details. The polarization domain does not provide the same resolution capabilities as the other domains, when exploited alone. The simulations verify the superiority of the joint spectrum and coincide with the theoretical analysis. It is shown that the joint spectrum outperforms the spatial spectrum in characteristic detection and estimation.

Statistics of the Polarimetric Weibull-Distributed Electromagnetic Wave

The statistical properties of partially polarized light in Gaussian stochastic plane wave fields have been reported in the literature. In this paper, we examine the statistics of the stochastic plane electromagnetic (EM) wave fields that are Weibull distributed. The polarimetric Weibull-distributed wave is characterized by three parameters: the sum of the intensities of the two electric vector components, the orientation angle that the major axis makes with the reference coordinate system, and the ratio of the minor to the major axis. The joint and marginal probability densities of these random variables are determined as a function of the covariance matrix. The main properties of this important distribution are shown. Then, the statistical properties of the normalized Stokes parameters are described in detail in Weibull-distributed stochastic fields. The joint and marginal probability density functions of the three components of the normalized Stokes parameters are presented. Numerical simulations are operated, which coincide with the theoretical derivations. Comparisons between Gaussian and Weibull stochastic fields have been made. The presented statistics of the Weibull polarimetric wave will be useful to random medium scattering and speckle filtering, which can also be extended to deal with the characterization of the scattering matrix elements in radar polarimetry.

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.

CFAR detection based on PDF estimation of clutter

In this paper we propose a new CFAR (constant false alarm rate) detector whose detection threshold is calculated based on the PDF (probability density function) estimation of clutter. Two schemes for the proposed detector are introduced, which use the Padé approximation method and the maximum entropy (MaxEnt) method respectively to estimate the PDF of clutter. The two schemes are verified in Weibull clutter through simulation experiments, and the results show that, the proposed CFAR detector performs as well as the maximum likelihood (ML) CFAR detector in uniform Weibull clutter, and it can adapt to other types of clutter without changing the detectors structure.

A novel approach of countering centroid jamming by using INS information in terminal guidance

During anti-ship missile (ASM) tracking ship in terminal guidance phase, echo in monopulse radar seeker receiver was generated by modeling chaff and ship as Swerling II and Swerling IV in chaff centroid jamming scenario, respectively. A generalized likelihood ratio test (GLRT) algorithm was then proposed for chaff detection in the main-beam. When the presence of the jamming was detected, one can combine target position forecast with inertial navigation system (INS) navigation solution to accomplish the homing guidance of ASM, and then when the absence of the jamming was detected, radar seeker capture and track target again, which could help achieve ones purpose of anti-jamming. Simulation showed that this method was effective and feasible due to its preferable anti-jamming performance.

New target detection method in strong active jamming background for polarimetric radar

A new method of target detection for polarimetric radar in the presence of strong active jamming is proposed. Based on analysis of the polarization characterizations of the signals received by polarimetric radar, the target detection is achieved through testing on the polarization information. Comparing with the traditional method of target detection made in time-frequency domain, the detection performance of the new method is improved because the influence of the strong active jamming is avoided. The performance of the new method is analyzed by simulation. Its validity is verified through outdoor experiment carried out by X-band polarimetric radar.