34 results about "Electric-field integral equation" patented technology

The invention discloses a method for simulating the wide-band electromagnetic scattering property of a conductor target. The method comprises the following steps that the geometric model of the conductor target is built, and mesh generation is conducted on the surface of the conductor target by a curved surface triangle unit; a time domain electric field integral equation of the conductor target is determined; a surface induction current in the time domain electric field integral equation expands through a space CRWG primary function and a time delay primary function; an expanding surface induction current expression is substituted into the time domain electric field integral equation, and then the time domain electric field integral equation in a discrete form is tested in a time and space mode so as to obtain a system impedance matrix equation; singularity integrals are eliminated to obtain a sparse expression of a impedance matrix; the equation of the impedance matrix is solved to determine the distribution of the time domain current of the surface of the conductor target, and wide-band electromagnetic property parameters of the target are obtained according to the distribution of the time domain current so as to finish simulation. The method for simulating the wide-band electromagnetic scattering property of the conductor target has the advantages of being high in simulation precision, little in required time and low in memory consumption, and has wide application prospect.

The invention relates to a method for determining the protection space between an ultra-high-voltage DC (direct current) transmission line and a wireless station. The method comprises the methods of constructing a passive jamming line-surface model of an ultra-high-voltage DC transmission line and solving an electric field integral equation corresponding to the model. The method comprises the following steps: firstly, constructing a passive jamming simulation surface model of the line according to the real space truss structure of transmission towers of the line, and constructing the passive jamming line-surface model of the transmission line in combination with the line model of an overhead wire and ground wire; solving induced current of each part of the ultra-high-voltage DC transmission line by using a moment method checked by RWG (Rao-Wilton- Glisson) basis function and Galerkin method, and calculating secondary radiation intensity vector generated by the induced current; and superposing the vector with a source electromagnetic filed to obtain the jamming level of the ultra-high-voltage DC transmission line to the wireless station. Comparison of test data obtained through the test proves that the method provided by the invention has higher accuracy, and can be used for accurately determining the passive jamming protection space between high-voltage transmission line and adjacent wireless stations in the future.

The invention provides a surface exciting method applicable to calculation of direction diagrams of waveguides in different shapes. The method comprises the following steps of: 1, setting an exciting surface of a shape corresponding to the shape of the cross section of a waveguide according to the the shape of the cross section of a waveguide; 2, dividing the exciting surface into even two-dimensional meshes, wherein an equivalent electric dipole source and a magnetic dipole source are arranged in the center of each mesh; 3, obtaining electric current of all the equivalent electric dipole sources and magnetic current of all the magnetic dipole sources on the exciting surface according to an equivalence principle, wherein an electromagnetic filed on the exciting surface is a main mode in which electromagnetic wave spreads in the waveguide; 4, carrying out mesh generation on the surface of the waveguide by virtue of triangular binning so as to obtain radiation fields generated by all the equivalent electric dipole sources, wherein the radiation fields serve as exciting fields of the surface of the waveguide; establishing an electric filed integral equation according to boundary conditions of the surface of the waveguide and obtaining the induction current of the surface of the waveguide by solving the equation according to a moment method; and 5, calculating the scattering direction diagram of the waveguide according to the induction current. Waveguides in different structures and shapes can be excited by the method provided by the invention instead of different methods separately.

The invention discloses an electromagnetic scattering analysis method of a target with a cavity on the basis of a moment method and a parabolic equation. The method comprises the following steps: firstly, filling the cavity body of the target with the cavity with solid metal, establishing a discrete model, determining the axial direction of a parabola as an x axis, and dispersing a target along the axial direction of the parabola by a mesh; in an x-axis direction, utilizing a CN (Crank-Nicolson) difference scheme to obtain a relationship between two adjacent tangent planes; in y-axis and z-axis directions, independently adopting an RPIM (Radial Point Interpolation Method) constructing fractal function and a spatial derivative to construct a matrix equation; successively carrying out recursive solving on a node electric field value on each tangent plane; carrying out solving on a cavity body part in the target separately by a fast multipole algorithm, applying an electric field integral equation to obtain current on the surface of the cavity body, and obtaining the electric field value of each discrete point required by the parabolic equation on an opening surface of the cavity body; and finally, carrying out postprocessing on the electric field on a last tangent plane to obtain a radar scattering sectional area. A meshless parabola and a fast multipole acceleration moment method are combined, and the electromagnetic scattering analysis method has the advantages of being efficient and reliable.

The invention discloses a simulation method for rapidly extracting transient scattered signals of an electric large-size metal cavity target. The simulation method includes creating a geometric model of the metal cavity target, and performing mesh dissection on the surface of the metal cavity target by a curved-surface triangular unit; determining a time domain integral equation of the metal cavity target; unfolding a surface induced current in the time domain integral equation by a high-order lamination divergence conformal basis function in terms of space and a time and space-time hybrid basis function in terms of time; substituting a surface induced current expression into the time domain integral equation, and testing a time domain electric field integral equation in a discrete form in terms of time and space respectively to acquire a system impedance matrix equation; solving the impedance matrix equation by a time stepping method, determining time domain current distribution on the surface of the conductor target, and acquiring broadband electromagnetic characteristic parameters of the target according to time domain current distribution to complete simulation. The method has the advantages of high simulation accuracy, less time used and low memory consumption, thereby having a broad application prospect.

The invention provides a laminated matrix decomposition-based low frequency electromagnetic property simulation method. Firstly, the problem of low frequency collapse of the conventional electric field integral equation method is eliminated by employing an augmented electric field integral equation method; a low frequency multi-level fast multi-pole method is adopted to establish a laminated matrix expression for the coefficient matrix of the augmented electric field integral equation; the laminated matrix is further compressed by using a double compression method to remove redundant information; finally, a laminated matrix format algorithm is adopted to perform upper-lower triangular decomposition on the compressed laminated matrix. The laminated matrix decomposition can reduce calculating complexity and memory consumption to be almost linear; a precondition technology is constructed for an iteration solution and a direct solution is constructed. The method has the advantages of high solving speed, low memory consumption and precision controllability and can be applied to various kinds of low frequency electromagnetic property analysis.

The invention discloses a numerical method of satellite electromagnetic scattering characteristics within a millimeter wave band. Aiming at such a metal and medium mixed structure of a satellite, an electric field integral equation is established only for the metal part of the satellite, an equation does not need to be established for the medium part, and finally, an equation with good conditions is formed, so as to be convenient for iterative solution. Mesh generation is performed only on the metal surface of the satellite, the mesh generation does not need to be performed on the medium coated part, and the strangeness is easily processed. Because of a structural feature of the inclined long satellite, the directionality of a transfer factor component is strong, an acceleration method is adopted for a far field effect on the basis of a multi-level fast multipole algorithm, computational memory requirements are effectively reduced, and the computing time is saved.

The invention discloses a frequency angle two-dimensional mixed interpolation based rainfall particle scattering operation accelerating method. A cubic spline interpolation method and Stoer-Bulirsch are combined as a model, a RCS (radar cross section) contains frequency and angle information, and RCS acquisition at frequency and angle zones of interested wave bands is repeated. The method is characterized in that cubic spline interpolation is applied to wide-induced-current angle zones, and Stoer-Bulirsch is applied to wide frequency zones. In order to effectively calculate electromagnetic scattering characteristics and improve operation efficiency of matrix-vector multiplication in an electric field integral equation, SM/CG (sparse matrix/canonical grid) is applied. By adoption of the method, operation time is greatly saved in frequency and angle scanning, and rainfall particle swarm bandwidth scattering operation speed is increased effectively.

The invention discloses an electric field generating device and an electric field fresh-keeping refrigerator. A boost circuit is utilized to output an alternating current voltage, for example, 220 V can be boosted into alternating current voltage of 1,000-8,000 V through a rectifier circuit; an energy field can be generated through vibration due to electric field interaction between high voltage electrodes in the device, the proper energy field can be combined with the refrigerator, so that the activity of the free radical scavenging systems (including SOD, POD, CAT and other various antioxidant enzymes) in fruits and vegetables at the proper energy field environments can be strengthened, the generation and removing of free radicals are returned to balance again, and therefore, the shelf life of the fruits and vegetables can be prolonged; and a negative ion generator is connected, and plasma active substances can be generated through the discharging of the negative ion generator, so that skin bacterial viruses can be further killed on the basis of the fresh-keeping of food.

The invention discloses an electromagnetic scattering no-grid simulation method for an appearance-complicated metal target, which comprises the following steps that local integral domains of nodes are established: the local integral domain at the periphery of each node is constructed by a region growing algorithm according to distribution information of the discrete nodes on the surface of the appearance-complicated metal target; an electric field integral equation of the metal target is established; surface current at the discrete nodes is decomposed; surface current in the center of each integral domain is constructed; the electric field integral equation is tested by point matching; an impedance matrix equation is obtained and solved; a current coefficient is obtained; and a radar cross section is determined according to the current coefficient. The method is independent of modeling grid subdivision on the surface of the target; quick electromagnetic scattering simulation can be conducted on the target only after the distribution information of the discrete nodes on the surface of the target is known in advance; an implementation process of the method is flexible and free; and the method has a very high practical engineering application value.

The invention relates to an impedance load point selection method for electromagnetic scattering of high tension overhead transmission lines. The method comprises that (1) an electric field integration equation of induction current generated by excitation of a metal conductor incident field of the transmission lines is established; (2) the electric field integration equation is converted into a metal-conductor matrix equation set based on a matrix method; (3) an overhead-line matrix equation set is established based on frequency-domain multi-conductor transmission line method; (4) a mixed equation set of the metal-conductor matrix equation set and the overhead-line matrix equation set is established; and (5) the impedance load point of electromagnetic scattering of the high tension overhead transmission lines is selected according to the mixed equation set. The provided method is highly accurate, and can be used to select the optimal load point when the electromagnetic scattering for electromagnetic waves of specific frequency of the high tension transmission lines is inhibited, and thus, electromagnetic scattering for different types of radio stations of the high tension transmission lines can be inhibited in an economical and efficient way.

The present invention discloses a prediction method of antenna pattern disturbances on an electrically large platform. Firstly, a geometrical model of an antenna and an electrically large platform is established and grid division is performed on the model; secondly, an electric field integral equation is established according to boundary conditions, antenna and electrically large platform surface sensing current is represent by a spherical wave phase primary function, the electric field integral equation is tested through a galerkin approach to obtain a matrix equation system, solving the matrix equation system to obtain a current expansion coefficient; and ultimately, calculating a disturbance pattern of the antenna. With adoption of the prediction method, division grids of the electrically large platform and the antenna structure can be greatly reduced, thereby saving computing resources.

A method for stably solving an electric field integral equation in a time domain is disclosed. Another form of a thin-line time-domain electric field integral equation suitable for a finite differencesolution is deduced, and in the fine wire structure, symbols shown in the description are considered to be the line current and charge density respectively. The invention does not need to introduce an expansion function, directly discretizes the temporal and spatial differentials of the unknown current, and further advances the solution in time.

The invention discloses an adaptive nested crossover approximation method for analyzing low-frequency electromagnetic characteristics. The method comprises the steps of firstly extracting a grid fileof an electromagnetic analysis target, and setting an incident electromagnetic wave parameter; secondly grouping to-be-analyzed target grids by adopting an octree according to an average grid number in each group, defining discrete grids and groups where the discrete grids are located, and performing statistics on a basis function number in each non empty group; thirdly establishing a subordination relationship between the groups of adjacent layers, establishing an electrical field integral equation in a discrete grid region, and dividing the region into a near-field region and a far-field region according to the distances between the groups; fourthly calculating an impedance matrix formed between the non-adjacent groups by adopting the adaptive nested crossover approximation method; and finally obtaining a solution of the electrical field integral equation through iterative solving, thereby obtaining the low-frequency electromagnetic characteristics. The method has the advantages of stable low-frequency value, simple programming realization and high calculation efficiency, and realizes efficient analysis on the low-frequency electromagnetic characteristics.

The invention discloses a simulation method of a three-dimensional electromagnetic heat effect based on a regional decomposition method, which comprises the following steps: firstly, establishing a simulation model for a target structure, dividing the simulation model into a plurality of complementary overlapped sub-regions, and then performing grid dispersion; secondly, establishing an electric field control equation set of the sub-regions based on the time-coordinated electromagnetic field characteristics, introducing continuity conditions and electric field Lagrangian multipliers on interfaces of the sub-regions, and obtaining electric field distribution conditions of the sub-regions by solving the electric field Lagrangian multipliers; wherein ohmic loss of a consumed medium in each sub-region is taken as a heat source of excitation heat, a convection boundary condition is adopted in each sub-region for truncation; determining a thermal control equation based on a heat conduction characteristic, and meanwhile, introducing a thermal field transmission condition and a thermal field Lagrangian multiplier into an interface of each sub-region; and finally, introducing a thermal field Dirichlet pre-condition technology, accelerating the iterative solution of the thermal field Lagrangian multiplier, and obtaining the thermal field distribution condition in each sub-region. The method is wide in application range, high in convergence speed and high in solving precision.

The invention discloses a method for analyzing the electromagnetic scattering of a complex target through an MDA (Model-Driven Architecture) and an MLSSM (Multilevel Simply Sparse Method). The method comprises the steps of: at first, establishing an octree structure of a target object, obtaining, through the MDA method, a far-field action portion corresponding sparse low-rank representation in a dense impedance matrix formed by a discrete electric field integral equation, then by using the improved MLSSM, representing the low-rank-represented portion in the impedance matrix, and in the end, on the basis of the improved MLSSM representation, constructing an algorithm for rapidly calculating matrix-vector product, which is suitable for iterative solution. The method can greatly reduce the calculation time and the memory requirement which are required by using an electric field integral equation method for analyzing the electromagnetic scattering of the complex target.