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Study on Moving Target Polarization Characteristic Measurement and Polarization Radar Anti-jamming Techniques

Author: LiuYong
Tutor: WangXueSong
School: National University of Defense Science and Technology
Course: Information and Communication Engineering
Keywords: moving target polarization characteristic measurement waveform design fully polarimetric orthogonal frequency diversity multiplex (OFDM) waveform instantaneous polarization polarization anti-jamming instantaneous polarization radar orthogonal polarization dual array radar polarization inverse synthesis aperture radar(ISAR) polarization cancelling polarization discrimination
CLC: TN953
Type: PhD thesis
Year: 2011
Downloads: 112
Quote: 1
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Abstract

Polarization information can remarkably improve radar performances of target detection, target recognition and anti-jamming, and has wide application perspectives in modern surveillance and missile defence radars. However, with the appearance of novel maneuvering targets and the more and more complicated electromagnetic (EM) environment, the effective applications of radar polarization information face many challenges. On the one hand, the fast movement of such targets as missiles and airplanes make their polarization characteristics fluctuate more acutely, so the inherent drawback of tradiational alternative polarization measurement scheme has become the main obstacle for acquiring their polarization information. On the other hand, with the appearance of various advanced coherent and wideband electronic counter measures (ECM), available polarization anti-jamming methods are unable to counter sophisticated jamming types due to their limited application conditions. Under the background of air surveillance and missile defence, the polarization characteristic measurement methods of moving targets as well as the polarization radar anti-jamming methods are deeply studied based on the instantaneous polarization theory. The main contents of this dissertation include:In the aspect of target polarization characteristic measurement: To acquire the polarization characteritics of fast moving targets such as missiles and airplanes, the simultaneous polarization measurement method is deeply studied, which can remarkably improve measurement performance.(1). Taking missile targets as an example, their narrowband and wideband polarization characteristics under movement condition are analyzed, and then the modulation mechanism of fast movement on target polarization characteristics is revealed. For alternative polarization measurement shcheme and simultaneous polarization measurement scheme, the effect of target polarization characteristic fluctuation on their measurement performance is quantively analyzed. The results of theorectical analysis and simulations show that simultaneous polarization measurement scheme have prominent advantage for targets with fast fluctuating polarization characteristics. This conclusion provides valuable reference for the choice of polarization radar schemes.(2). To measure the narrowband polarization characteristics of moving targets, the isolation performances of frequency shifted pulse waveform and up-down slope LFM waveform are comparatively analyzed. The results show that better measurement performance can be achieved for frequency shifted pulse waveform when the doppler shift compensation error is small. Field measurement experiments using instantaneous polarization radar (KD-IPR) are performed to prove corresponding conclutions.(3). To measure the wideband polarization characteristics of moving targets, fully polarimetric OFDM waveform is designed based on the principle of orthogonal frequency diversity multiplex (OFDM), and its processing methods are given, including wideband polarization scattering matrix (PSM) measurement and one dimensional/two dimensional full polarization characteristic extraction. The analytical results show that this waveform has better isolation performance compared with traditional wideband up-down slope LFM waveform after velocity compensation, so it can extract target full polarization information more accurately, and can eliminate the“doppler-delay”coupling error as well.In the aspect of polarization radar anti-jamming: For the applications of surveillance, guidance and imaging, several practical polarization radar anti-jamming methods are studied for typical jamming types such as active decoy, self-defence active jamming and wideband jamming.(1). To counter active decoy jamming, the suppression algorithm is put forward based on the instantaneous polarization characteristic differences between target echoes and jamming signals. Compared with available methods, the new method doesn’t need to estimate jamming polarization state, so it is more practical. The results of experiments based on the measured target echoes show that this method can also obtain effective anti-jamming performance under relatively low signal to noise ratios (SNR)/jamming to noise ratios (JNR).(2). To counter self-defence active jamming, the spatial polarization theoretical model of orthogonal polarized dual array radar antenna is established, and then two novel spatial polarization anti-jamming methods are put forward. Firstly, the spatial virtual polarization filtering process is given, which can estimate jamming polarization state by only using the received signal amplitude and counter self-defence suppressive jamming effectively. Secondly, the spatial polarization discrimination method for active decoy is studied. Based on the spatial polarization characteristic differences between target echoes and jamming signals, the processing algorithm is designed to counter self-defence deceptive jamming. The simulation results prove the effectiveness of above two anti-jamming methods.(3). To counter the wideband active jamming of inverse synthesis aperture radar (ISAR), two wideband polarization anti-jamming methods are put forward. Firstly, according to the criterion of minimizing the average jamming signal power in radial range dimension, wideband adaptive polarization canceling (WAPC) algorithm is given, which can effectively counter wideband suppressive jamming. Secondly, using the high resolution range profile (HRRP) polarization correlation characteristic differences between real targets and false targets, the polarization discrimination algorithm is advanced, which can effectively counter wideband HRRP deceptive jamming. These two methods can improve the imaging ability of ISAR under jamming background.The research results of this dissertation are useful for promoting the instantaneous polarization information applications from theory to practice, and are of important reference value for advancing the performances of defence radars in target characteristic acquisition and anti-jamming.

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