When there is Doppler ambiguity number mutation,keystone formatting is no longer valid because of integration performance deterioration and false velocity estimation.A novel keystone formatting method based on non-baseband interpolation is presented.It has a different half blind velocity range comparing with normal keystone formatting.Furthermore,there is non-superposition between half-blind-velocity-range of keystone formatting based on baseband and that of non-baseband interpolation.So a synthesizing keystone formatting is proposed to avoid the half-blind-velocity effect.Simulation results of the proposed method show that integration deterioration and velocity estimation falsity can be eliminated effectively.
Based on the theory of phase complement,an anti-cloak with circular cross section can be made invisible to an object outside its domain.As the cloak with elliptic cross section is more effective to make objects invisible than that with circular cross section,a scaled coordinate system is proposed to design equivalent materials of invisible anticloak with elliptic cross section using phase complement.The cloaks with conventional dielectric and double negative parameters are both simulated with the geometrical transformations.The results show that the cloak with elliptic cross section through phase complement can effectively hide the outside objects.
Based on the local configuration angle division to select the corresponding method for electromagnetic scattering calculation from rough sea surface,this paper presents an angular cutoff composite model:when the local scattered angle is in the specular region that is given by an approximately 20 degrees cone around the specular direction,the Kirchhoff approximation is applied to evaluate the specular reflection,which dominates the total scattering in this region;the small perturbation method is employed to handle the diffuse reflection which is predominant as the local scattered angle is situated out of the specular region.Numerical results are compared with those of experimental and theoretical models in several configurations as a function of incident angle,wind speed,wind direction.The comparison of numerical results of other experimental and theoretical models in several configurations shows that the new composite model is robust to give accurate numerical evaluations for the sea surface scattering.
Target modeling and scattering function calculating are important prerequisites and groundwork for the synthetic aperture radar(SAR) imaging simulation.According to the difficult problems that normal methods cannot calculate the scattering function of electrically large object under the condition to wideband,an effective method of improved equivalent edge currents is presented and applied to SAR imaging simulation for the first time.This method improves calculating velocity and has relatively high precision.The concrete steps of applying the method are given.By way of the simulation experiment,the effectiveness of the method is verified.
An iterative method in the Kirchhoff approximation is proposed for high frequency multiple electromagnetic scattering from two-dimensional dielectric sea surface.The multiple interaction of the scattering field is characterized with the corrected electromagnetic currents of the wind-driven sea surface.The actual surface currents are approximated with the iterative solution of the corrected currents.A newly developed sea spectrum,Elfouhaily spectrum,is utilized to build the sea surface model.The shadowing correction is improved by the Depth-Buffer algorithm.The validity of the iterative Kirchhoff approximation is verified by the agreement of backscattering coefficients with the measured data.
