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FDTD Improved Algorithm And Testing Technology For Complex Target’s Electromagnetic Scattering

Posted on:2016-07-18Degree:DoctorType:Dissertation
Country:ChinaCandidate:Z S GuanFull Text:PDF
GTID:1222330503976403Subject:Precision instruments and machinery
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The confrontation between stealth and anti-stealth has a extremely important role in modern electronic warfare. The research about electromagnetic scattering of target is the base of designing and developing stealth weaponry, anti-stealth radar system and weapon assessment. In order to obtain the target’s electromagnetic scattering data, the means of theoretical calculations and experimental tests are needed. A higher reliability’s data could be obtained, especially when the complicated target needs to be verified. This thesis is focus on these two aspects. In terms of theoretical calculations, the thesis ameliorates the traditional Finite-Difference Time-Domain method. The stability conditions of the algorithms is weakened. EMS memory is reduced and computational efficiency is improved when using the ameliorated and distorted methods to compute. Then based on this work, the electromagnetic characteristics of the certain plane is simulated and computed by using the ameliorating and distorting algorithms. In the part of experiment testing, the method of testing outfield static、dynamic RCS is explored and researched. and the method of error estimation with GPS is applied to obtain the exact location of the measured object. The confidence level of test data is improved. The cost of test is reduced. Finally, the simulation results with the testing results is compared, both show a better similarity, and thus, the feasibility of obtaining the electromagnetic characteristics of the large-scale objects by using the methods proposed in the paper is proved. The contents of the thesis contains several aspects as follows:1.The basic principle of the Finite-Difference Time-Domain methods and the key elements involved in the computation are researched, and the wave absorption efficiency among PML、UPML and CPML in the FDTD methods is analyzed. Then the paper decides introducing CPML to the methods that will be studying in the following chapters.2.The Alternating Direction Implicit Reduced Finite-difference Time-Domain algorithm (ADI-R-FDTD) is proposed, the basic difference formula of the ADI-R-FDTD algorithm in the 2-D TE model and 3-D wave is derived in detail, and the stability conditions and numerical dispersion are researched. An implementation of CFS-PML using auxiliary differential equation (ADE) for ADI-FDTD is developed, and its absorbing properties has been compared with other absorbing boundary conditions. It combines ADI-CPML with ADI-R-FDTD, through numerical example, the results show that ADI-R-FDTD algorithm is better than the traditional FDTD algorithm and ADI-FDTD algorithm in the aspects of EMS memory and computational time when computing.3.An hybrid implicit-explicit FDTD (HIE-FDTD) method is proposed, The basic difference formula of the HIE-FDTD algorithm in the 2-D TE model and 3-D wave is derived in detail. An implementation of CFS-PML using auxiliary differential equation (ADE) for HIE-FDTD is developed, their idiographic difference formula have been proposed and its absorbing properties has been compared with other absorbing boundary conditions. Sherman-Morrison is used to solve the non-tridiagonal problem and the large-sparse matrix has been transformed to tridiagonal equation and its computational complication has been predigested largely when the HIE-FDTD method has been used to solve the electromagnetic characteristics of the periodic structure.4.Full-scale horizontal-field measure methods with real time emendation is put forward, based on the relative calibration, distance wave gate has been set up to measure the corrector’s RCS, and which reduces the error caused by the time’s non synchronization between calibration and measure. The method of single frequency error estimation used in testing could gain more accurate RCS measurements, and reduce the cost of test. The flow and scheme for the whole waveband static-test has been made. The static RCS datum of the target is get. Through lay outing the lane of the plane, the statistics complexity of dynamic datum is decreased effectively, the flow and scheme for the dynamic-test has been made, finally the dynamic RCS datum of the target is get, and the test data is processed and analyzed.5.The computational model about ADI-R-FDTD algorithm and HIE-FDTD algorithm of this type aircraft is established. Its radar cross section (RCS) simulation data is obtained, and the two methods’ relative error and computational efficiency are compared. Then the computational results have been compared with the testing results. Which shows that the simulation results and the testing results have a high similarity, so it is proved that the proposed methods can be used to compute the large-scale objects’ electromagnetic scattering characteristics.
Keywords/Search Tags:electromagnetic scattering, Finite-Difference Time-Domain, Alternating Direction Implicit Reduced, Hybrid Implicit-Explicit, unconditionally stable
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