Investigation On Composite Electromagnetic Scattering From Target And Sea Surface With Overturning Waves By Iterative Physical Optics Algorithm

In recent years,with the development of ocean remote sensing and target detection and recognition technology in the ocean environment,the scattering of sea surface and composite scattering from sea surface and target have been concerned by scholars at home and abroad.In the paper,the two respects are investigated that the electromagnetic scattering of sea surface with overturning wave and composite electromagnetic scattering from sea surface and targets.The electromagnetic scattering of 1-D and 2-D rough surface with overturning wave is solved by the iterative physical optics(IPO).And based on the multi-path scattering and the principle of equivalence,the composite scattering from 1-D sea surface with overturning wave and 2-D target,and 2-D sea surface with overturning wave and 3-D target are investigated by the combined method of physical optics and iterative physical optics(PO-IPO).The main work of this paper includes the following parts:1.Electromagnetic scattering of 1-D rough sea surface under high sea state.Based on the principle of iterative physical optics(IPO)method,the formula for calculating the electromagnetic scattering coefficient of 1-D rough sea surface under high sea state is derived with HH polarization in detail.The electromagnetic scattering characteristics of sea surface under different wind speeds and polarizations are studied and compared with the numerical results of traditional moment method(MOM)and PO.The results show that compared with PO method,the calculation results of IPO Method and MOM method are in an excellent agreement.2.Electromagnetic scattering of 1-D rough sea surface with overturning wave.Because PO method is not accurate enough to calculate the electromagnetic currents of rough sea surface,a more accurate IPO method is used to calculate the electromagnetic scattering of 1-D sea surface with overturning wave.Based on the Fournier wave model,considering the influence of wind speed on wave length and height,an improved time-varying overturning wave model is established.Then the actual PM spectrum sea surface and time-varying wave under the same wind speed are spliced to establish a 1-D sea surface geometric model with single overturning wave or multiple overturning waves at different times.The IPO method is used to calculate the electromagnetic scattering of 1-D sea surface with overturning wave,and the coupling effect between the surface elements is taken into account in this method.The numerical results are compared with those of the traditional moment method(MOM).And the two methods have good consistency in the small and medium scattering angle.The electromagnetic scattering characteristics of the sea surface at different polarizations,times and number of waves are analyzed in detail.3.Composite electromagnetic scattering from 1-D rough sea surface with overturning wave and 2-D target.Based on the multi-path scattering and the principle of equivalence,the PO-IPO method is used to calculate a composite electromagnetic scattering model of 1-D sea surface with overturning wave and 2-D target.In this algorithm,PO method is used to calculate the scattering of target,IPO method is used to calculate the electromagnetic scattering of sea surface with overturning wave,and the coupling scattering between them is solved by the equivalent theory from near-field to near-field.The composite electromagnetic scattering of 1-D sea surface with overturning wave and 2-D target are calculated for different polarizations,different target types and different number of waves in detail,and compared with the results of traditional moment method(MOM).At the same time,the composite electromagnetic scattering coefficient under the above-mentioned different parameters is analyzed.4.Composite electromagnetic scattering from 2-D rough sea surface with overturning wave and 3-D target.Firstly,based on 1-D time-varying overturning wave geometry model,the 2-D overturning wave model is developed on the y-axis.And the 2-D local sea surface geometry model with overturning wave is established.The formula of 3-D IPO method is derived,and the electromagnetic scattering of 2-D overturning wave is solved.The results are compared with those of MLFMM in FEKO software,and the validity of three-dimensional IPO method is verified.Then,the PO-IPO formula of the composite model of the 3-D target and the 2-D local sea surface with overturning wave is derived,and the electromagnetic scattering characteristics of the missile target above the 2-D sea surface with overturning wave are studied.