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Research On Polarization Matching Theories And Techniques For Target Detection In Differentenvironments

Posted on:2016-06-04Degree:DoctorType:Dissertation
Country:ChinaCandidate:S W LeiFull Text:PDF
GTID:1108330473456078Subject:Signal and Information Processing
Abstract/Summary:PDF Full Text Request
Target detection problem in different environments is one of the fundamental problems in radar, sonar and navigation fields, etc. With the applications of stealth material and stealth technology in countermeasure activities, target radar cross section(RCS) decreased, target echo weakened, signal to noise ratio(SNR) reduced. Therefore they would seriously degrade the detection performance of the detection system. Polarization scattering property of target makes the target echo to different polarized electromagnetic wave different. The optimally selecting of the electromagnetic wave polarization direction to match the target scattering characteristics is one effective method to increase the target polarized echo; hence, it can improve the detection performance.This thesis researches the deterministic target detection problem and fluctuating target detection problem in partially homogeneous environment, inhomogeneous environment and system-dependent clutter environment. New adaptive detectors are proposed.To take a step further, the detection performance of these proposed detectors is theoretically analyzed. Polarization matching detectors are designed to further improve the detection performance with the aid of polarization matching technology. The main contributions of the thesis are illuminated as follows.1. Fast polarization matching methodIn coherent condition, the polarization receiving power(PRP) of the antenna is described by a 2 × 1 dimensional Jones vector and a 2 × 2 dimensional Sinclair matrix.With the aid of(generalized) Rayleigh Quotient principle, the maximum PRP and its corresponding matched(optimum) polarization state can be obtained. In incoherent condition, the PRP of the antenna is described by a 4 × 1 dimensional Stokes vector and a4 × 4 dimensional Kennaugh matrix. In this condition, fast polarization matching methods for two types of transceiver polarized constrained conditions are researched. For the condition that transmitter and receiver have the same polarization state, a Lagrange method based on bisection strategy(LMBS) is proposed. Given the value domain of the Lagrange multiplier, the LMBS effectively accelerates the matching procedure by utilizing the bisection algorithm. For the condition that the polarization states of the transceiver are unconstrained, a fast subregion search method(FSSM) with the aid of space mapping theory is proposed. The FSSM reduces the searching area into a smaller subregion and effectively accelerate the polarization matching. Theoretical analysis shows that the area of the subregion is no more than a quarter of that of the whole region.2 Polarization matching detection methodsTo the target detection problem in partially homogeneous environment, an adaptive matched detector for partially homogeneous background(PH-AMD) is proposed. Based on the generalized likelihood ratio test(GLRT) principle, the PH-AMD estimates the target x by assuming that the scaling parameter κ and noise covariance matrix R are temporarily known a priori. κ is estimated through primary data and secondary data, and R is estimated through secondary data. The test statistic is constructed by using these estimations of the unknown parameters. The detection performance of the PH-AMD for both deterministic and fluctuating targets is theoretically analyzed. The analyses show that the PH-AMD is a constant false alarm rate(CFAR) detector. The theoretical results show that the detection probability is directly proportional to the parameter μ and μ is related with the polarization state of the electromagnetic wave. With the aid of polarization matching technology, a polarized matching detector is designed by choosing the polarized electromagnetic wave to matches the target polarization property. Experiments show the polarization matching PH-AMD can further improve the detection performance and obtains a processing gain of 1 dB- 5 dB.To the target detection problem in inhomogeneous background, two detectors, i.e.,the adaptive matched detector for inhomogeneous background(IH-AMD) and one-step GLRT detector(1S-GLRT), are proposed. The design principle of IH-AMD is the same as that of PH-AMD while the design of the 1S-GLRT is based on the probability density function(PDF) of measurement data, i.e., fy(y). First, the PDF fy(y|κ) is obtained through the PDF of texture parameter κ, i.e., f IG(κ, α, β), and the conditional PDF fy(y|κ). Based on the GLRT principle, the target x and R are estimated through primary data and secondary data. The test statistic of the 1S-GLRT is constructed by using these estimations of the unknown parameters. The detection performance of the IH-AMD and 1S-GLRT for both deterministic and fluctuating targets is theoretically analyzed. Analyses results show that IH-AMD is a CFAR detector while the 1S-GLRT is an approximate CFAR detector only when the scaling parameter β is large enough(1/β → 0). Besides, the proposed detectors perform better than the published detectors.The analyses also show that the detection probabilities of the IH-AMD and the 1S-GLRT are both directly proportional to the parameter μ. With the aid of polarization matching technology, polarization matching detectors are designed to match the target polarization property and the polarization state of electromagnetic wave. Experiments show the polarization matching IH-AMD/1S-GLRT can further improve the detection performance and obtains a processing gain of 0 dB- 5 dB.To the target detection problem in system-dependent clutter(SDC) background, an adaptive subspace detector for SDC background(SDC-ASD) is proposed. The SDCASD takes the advantage of the subspace property of the clutter and separately deals with the clutter and the noise to obtain the processing gains. The detection performance of the SDC-ASD for deterministic target and fluctuating target is theoretically analyzed. Compared with the published detectors, SDC-ASD always performs better at different clutter conditions. In addition, the SDC-ASD requires less secondary data to obtain reliable performance. Since the detection probability of the SDC-ASD is directly proportional to parameter μ, polarization matching technology is applied to make the polarization state of the electromagnetic wave match the target scattering characteristics to further improve the detection performance. Experiments show the polarization matching SDC-ASD can obtain a processing gain of 1 dB- 3 dB.
Keywords/Search Tags:Target Detection, Polarization Matching Theories and Techniques, Partially Homogeneous Environment, Inhomogeneous Environment, SystemDependent Clutter Environment
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