A kind of accurate 3 D electromagnetic environment geometric modeling and parallel method based on Parabolic Equation
Technical field
The present invention relates to a kind of accurate 3 D electromagnetic environment geometric modeling and parallel method based on Parabolic Equation, take the technology such as electromagnetic propagation and Solving Partial Differential Equations as support, to solve complex electromagnetic environment simulation problems, the new electromagnetic environment emulation computing system that the demand of the aspects such as such as early radar warning, confrontation between systems, wireless communication network optimization, GPS location is object, belongs to computer realm.
Background technology
Along with the development of electronic technology and the widespread use of electronic equipment, electromagnetic environment emulation technology is paid attention to day by day.Electromagnetic environment emulation for the radar research of many bases, electronic countermeasure, navigational guidance systems reliability analysis, mobile communications network is made rational planning for and electromagnetic environmental effects analysis, the electromagnetic radiation pollution monitoring etc. of optimization, microwave relay station addressing, electronic equipment are significant.How quickly and accurately the large region of emulation complex electromagnetic environment has become one of focus of current research.
Calculate for electromagnetic environment emulation, people have proposed several different methods at present, as the empirical method based on experiment statistics data, deterministic models method etc., but in the time relating to large-scale complex electromagnetic environment calculating, under existing development of computer level, parabolic equation method can obtain better result of calculation compared with other Deterministic Methods.Parabolic Equation (Parabolic Equation, hereinafter to be referred as PE) method is one of Computational Electromagnetic Methods obtaining in recent years extensive concern, compare other many Computational Electromagnetic Methods, PE method has shown the not available special performance of other method in the tropospheric radio propagation Predicting Performance Characteristics of long-distance large-range and the RCS of Electrically large size object calculating: PE itself has embodied radio wave refration and diffraction effect, need not calculate the region of various mechanism of transmission in radio wave propagation process and loaded down with trivial details criterion again; Succinct and accurately to the processing of complex-terrain and inhomogeneous atmospheric refraction characteristic, while calculating large regional field overdamp characteristic, computational accuracy is high and speed is fast compared with additive method.From at present both at home and abroad correlative study, the correlative study based on two-dimentional scalar PE method reaches its maturity with application, and the theoretical research of three dimensional parabolic equation method and the demand that is applied in the higher situation of Electromagnetic Calculation accuracy requirement are urgent.As one of effective ways of electromagnetic environment three-dimensional artificial on a large scale, the calculating Space-time Complexity of three-dimensional PE method is still very large.In conjunction with the High Performance Computing that has huge impetus to calculating electromagnetics, to set up and there is the more high-efficiency electromagnetic realistic model of high degree of parallelism, the parallel algorithms in research simulation process, is the effective method that improves simulation calculation efficiency.But, in the time processing complex electromagnetic environment emulation, due to some complicated mass data storage of needs, the calculating of initial fields, the operations such as the processing of complex-terrain and atmospheric strument, parallel computation is difficult to obtain good effect.
For the unacceptable problem of complexity computing time of the large simulation of domain of three dimensional parabolic equation model, the method of finding the 3 D complex electromagnetic environment emulation that a kind of complexity is lower becomes more and more urgent, we have introduced accurate three dimensional parabolic equation parallel simulation method, three dimensions is divided into mutual incoherent two dimension slicing by the method, then adopts the parallel computation of coarseness to complete fast calculating.
Summary of the invention
Goal of the invention: the problem such as low for 3 D electromagnetic environmental simulation method efficiency, computer capacity is little, a kind of accurate 3 D electromagnetic environment geometric modeling and parallel method based on Parabolic Equation is provided, because the microtomy adopting can become two-dimentional computational problem by complicated three-dimensional computations problem reduction, computation complexity is reduced greatly, computer capacity has had expansion greatly, simultaneously owing to having introduced parallel computation, the efficiency of computation process is improved greatly, and the final data precision obtaining is well positioned to meet the demand of practice.
The present invention proposes a kind of accurate 3 D electromagnetic environment geometric modeling and parallel method based on Parabolic Equation, solved complex environments such as early radar warning, confrontation between systems, wireless communication network optimization, GPS location in the demand of electromagnetic field distributed in three dimensions aspect.The basic thought of this method is the method for independent one by one two dimensional cross-section that three dimensions is split into, and utilizes Two dimensional parabolic stability equation method to carry out the electromagnetic propagation emulation in section.Accurate three-dimensional method is take transmitter as the center of circle, by certain angle, three dimensions is split into independent one by one two dimensional cross-section, and utilizes Two dimensional parabolic stability equation method to carry out the electromagnetic propagation emulation in section.The structure of accurate tridimensional processes realistic model, not coupling between each section in each computation process, the computing power of supposing parallel machine is unlimited, each section has a processor and the corresponding internal memory of monopolizing to calculate, each section in accurate three-dimensional section can complete within a certain period of time and solve calculating simultaneously so in theory, so the number that its parallel speed-up ratio is ideally processor, namely parallel efficiency 100%.This system mainly comprises four steps: choose certain subdivision angle the electromagnetism distribution two dimension slicing method in three dimensions is carried out to subdivision step, build the initial fields step of accurate three-dimensional method from antenna radiation pattern, the complex environment of complicated geographical environment and atmospheric strument is carried out to accurate three-dimensional dividing step, and coarse grain parallelism method is carried out accelerating step to each section computation process.
Choose certain subdivision angle the electromagnetism distribution two dimension slicing method in three dimensions is carried out to subdivision step: refer to the electromagnetism distribution two dimension slicing method in three dimensions is carried out to operate approximately.Calculated amount when directly carrying out three-dimensional computations is too large, adopts two dimension slicing method to carry out approximate treatment and can reduce in a large number calculated amount, can't lose too many precision.Its specific implementation process is as follows: 1. two dimension slicing subdivision method: the method that by certain angle, three dimensions is split into exactly to independent one by one two dimensional cross-section; The acquisition methods of the angle of 2. cutting into slices: refer to the angle between can being cut into slices very easily with the ratio of the radius of known simulation precision and each section;
Initial fields step from the accurate three-dimensional method of antenna radiation pattern structure: when the subdivision of section completes, first need to have built from antenna radiation pattern according to antenna theory the initial fields of accurate three-dimensional method, its initial fields is on each section, to start Two dimensional parabolic stability equation to calculate required initial fields, subdivision is based on the far-field pattern of the field component in free space, and its equivalence only limits between three-dimensional scalar Parabolic Equation method and Two dimensional parabolic stability equation method.In realization, can first carry out discretize by sampling thheorem to Fourier transform, then adopt Fast Fourier Transform (FFT) to carry out numerical solution, obtain discrete initial fields;
The complex environment of complicated geographical environment and atmospheric strument is carried out to accurate three-dimensional dividing step: after the initial fields subdivision of accurate three-dimensional method completes, just need to start to calculate the propagation of electromagnetism in complex environment, at this moment first consider the impact on electromagnetic propagation of irregular landform, various landforms factor, the topographical surface of still describing from two-dimentional numerical map according to subdivision position angle, adopt suitable algorithm to extract the topographic relief line of one dimension, every of obtaining topographic relief line is the lower boundary in two-dimensional simulation section; Secondly,, in the time extracting topographic relief line, need to consider the interpolation method of the topographic profile of each section in slicing processes.In order arbitrarily to extract the topographic profile in map in the emulation of Parabolic Equation method, in employing piecemeal interpolation method, simple and effective bilinear interpolation algorithm calculates the height value of non-Nodes in numerical map.Finally, also need to consider that electromagnetic wave propagation aloft can produce effect of atmospheric refraction, for the roughly spherically stratified ionosphere feature of troposphere atmosphere, three-dimensional dividing is become two dimension by accurate three-dimensional method, utilizing refractive index rate of change is in height the feature of 1 to 3 magnitude of rate of change on surface level, by air index n (x, y, z) subdivision is approximated to n (x, z).In the time carrying out two dimension calculating, adopt three stage modes, this is a kind of accurate average mode, is the statistics obtaining after the atmospheric strument on differing heights is measured in a large number, generally on all height, can coincide finely with actual measurement mean value.
Coarse grain parallelism method is carried out accelerating step to each section computation process: in order to accelerate the calculating of above-mentioned all sections, this step is mainly ready-portioned two dimension slicing to be mapped to according to certain rule on the node of cluster, completes the solving etc. of initial fields, boundary condition, irregular atmosphere and landform, three Diagonal Equations of each section at each intra-node.Because the calculated amount difference of each section is little, so the node in each section and a group of planes carries out simple man-to-man mapping, greatly reduce so total execution time of algorithm.
Advantage of the present invention:
1. 3 D electromagnetic environment space has been carried out to two-dimentional division, thus the calculating of the high complexity while having avoided directly carrying out three-dimensional computations.
2. due to separate between the section after dividing, adopt the parallel method of coarse grain can obtain good speed-up ratio.
Accompanying drawing explanation
The basic module organization chart that Fig. 1 dicing method is realized;
The accurate three-dimensional slice method of Fig. 2 schematic diagram;
The subdivision schematic diagram of Fig. 3 initial fields;
The subdivision schematic diagram of Fig. 4 landform;
The irregular terrain profiles that on Fig. 5 DEM map, bilinear interpolation extracts;
Fig. 6 parallel computation structure schematic diagram;
Electromagnetic attenuation value schematic diagram in certain section of Fig. 7;
The three-dimensional visualization design sketch of the accurate three-dimensional method of Fig. 8;
The parallel time of the accurate three-dimensional method of Fig. 9 and speed-up ratio schematic diagram.
Embodiment
Below in conjunction with accompanying drawing, the present invention is described in further detail.
The present invention is a kind of accurate 3 D electromagnetic environment geometric modeling and parallel method based on Parabolic Equation, as shown in Figure 1.Mainly comprise four steps: choose certain subdivision angle the electromagnetism distribution two dimension slicing method in three dimensions is carried out to subdivision step, build the initial fields step of accurate three-dimensional method from antenna radiation pattern, the complex environment of complicated geographical environment and atmospheric strument is carried out to accurate three-dimensional dividing step, and coarse grain parallelism method is carried out accelerating step to each section computation process.
(1) choose certain subdivision angle the electromagnetism distribution two dimension slicing method in three dimensions is carried out to subdivision step
Calculated amount when directly carrying out three-dimensional computations is too large, adopts two dimension slicing method to carry out approximate treatment and can reduce in a large number calculated amount, can't lose too many precision, and this is just referred to as the three-dimensional method that is as the criterion.This method distributes the electromagnetism in three dimensions to carry out the method for operate approximately by two dimension slicing method, greatly reduces compared with the complexity in Direct Three-dimensional electromagnetism computation process.Its concrete dicing method is as follows:
1. three dimensions is carried out to the step of two dimension slicing.For large-scale electromagnetic environment emulation, three dimensional parabolic equation method still exists at present processes boundary condition and three-dimensional atmospheric structure complexity, and calculated amount is large, the problem that simulation time is long.And Two dimensional parabolic stability equation method can be predicted the electromagnetic propagation problem of emulation in the atmosphere two-dimensional space face of troposphere efficiently.Microtomy is take transmitter as axle center by 3 D electromagnetic communication space, be split into two-dimensional surface one by one according to certain angle, in each, carry out parallel computation electromagnetic propagation again with Two dimensional parabolic stability equation method, obtain the three-dimensional artificial visual effect of combination, its dicing method as shown in Figure 2.By approximate, avoid the complex calculation in three dimensional parabolic equation method like this, by the calculating of Two dimensional parabolic stability equation method, will greatly improve simulation efficiency.Meanwhile, in realization, adopt parallel computing, can obtain easily its parallelization and realize, obtain high parallel efficiency, support large simulation of domain.
2. need to determine the angle between section according to final simulation accuracy.In accurate three-dimensional method, simulation accuracy is embodied in the distance of two sections at the corresponding grid farthest time from transmitter, and this distance can, with the product representation of emission angle and transmitting radius, can obtain the angle between adjacent two sections in this way easily.In the case of the radius r of known simulation precision h and each section, the angle [alpha] between section can obtain with following formula: α=h/r.
(2) build the initial fields step of accurate three-dimensional method from antenna radiation pattern
First the general solution procedure of Parabolic Equation method is stepping iterative process, and to field source, modeling is equivalent to obtain the initial fields value problem of iterative computation, has built the initial fields of accurate three-dimensional method according to antenna theory from antenna radiation pattern.For accurate three-dimensional method, its initial fields is on each section, to start Two dimensional parabolic stability equation to calculate required initial fields, subdivision method as shown in Figure 3, antenna radiation pattern is the two-dimensional function of angle θ and Ф, from three-dimensional scalar Parabolic Equation, go out the two-dimensional radiation initial fields in each angle of radiation by three-dimensional antenna radiation pattern equivalence.Because above-mentioned subdivision is based on the far-field pattern of the field component in free space, its equivalence only limits between three-dimensional scalar Parabolic Equation method and Two dimensional parabolic stability equation method,, while application in actual propagation environment, accurate tridimensional processes has been ignored the coupling of polarization effect and each component.In realization, can first carry out discretize by sampling thheorem to Fourier transform, then adopt Fast Fourier Transform (FFT) to carry out numerical solution, obtain discrete initial fields.
(3) complex environment of complicated geographical environment and atmospheric strument is carried out to accurate three-dimensional dividing step
What this process was mainly considered is the subdivision process of complicated geographical environment and atmospheric strument.Shown in specific as follows:
1. geographical environment modeling mainly should be considered the impact on electromagnetic propagation of irregular landform, various landforms factor, and especially irregular topographic relief has material impact for mechanism of transmission such as electric wave reflection, diffraction.Through the subdivision to field source directional diagram, according to accurate three-dimensional method, the topographical surface of still describing from two-dimentional numerical map according to subdivision position angle, adopt suitable algorithm to extract the topographic relief line of one dimension, as shown in Figure 4, every topographic relief line is the lower boundary in two-dimensional simulation section.Consider the interpolation method of each section in slicing processes, although it is existing a lot of to read the business software of digital map data, but in order arbitrarily to extract the topographic profile in map in the emulation of Parabolic Equation method, herein on to the analysis foundation of USGS dem data storage format, work out data pick-up program.Press the distribution range of interpolated point, conventional interpolation algorithm can be divided into overall interpolation, piecemeal interpolation and pointwise interpolation three classes, adopt simple and effective bilinear interpolation algorithm in piecemeal interpolation method to calculate the height value of non-Nodes in numerical map here, and its difference approach as shown in Figure 5.
2. electromagnetic wave is aloft propagated and can be produced atmospheric strument subdivision method.Three dimensional parabolic equation method still cannot effectively be processed three-dimensional atmospheric structure at present.For the roughly spherically stratified ionosphere feature of troposphere atmosphere, three-dimensional dividing is become two dimension by accurate three-dimensional method, utilizing refractive index rate of change is in height the feature of 1 to 3 magnitude of rate of change on surface level, refractive index n (x, y, z) subdivision is approximated to n (x, z), wherein x, y, z represents the coordinate in three dimensions.Three stage modes are a kind of accurate average modes, it is the statistics obtaining after the atmospheric strument on differing heights is measured in a large number, generally on all height, can coincide finely with actual measurement mean value, only when refractive index n large (as n >=380), deviation be larger.Utilize any in three kinds of patterns, can process the refractive index n in standard Parabolic Equation easily.
(4) coarse grain parallelism method is carried out accelerating step to each section computation process
The implementation in turn of above-mentioned first three step by accurate three-dimensional method, has been split into independent one by one two-dimentional tangent plane by three dimensions, so just can utilize Two dimensional parabolic stability equation method to carry out the electromagnetic propagation emulation in section.It is carried out in parallel computation process, because each two-dimentional tangent plane is independent, there is no each other coupled relation, so each section can be assigned on the different nodes of a group of planes, between node, do not need communication, can realize high efficiency coarse grain parallelism.As shown in Figure 6, as seen from the figure, the node in each section and a group of planes carries out simple man-to-man mapping to its mapping method, because of nothing coupling between each section in the three-dimensional method that is as the criterion, compares with the parallel solution procedure of three dimensional parabolic equation, and degree of parallelism is high.On parallel machine, calculate without communication, also avoided the Design and implementation of complicated parallel algorithm.Then adopt MPI(message passing interface) concurrent program realization, parallel programming model is simple, on parallel machine, easily realize, electromagnetic attenuation value in certain section as shown in Figure 7, as shown in Figure 8, the parallel time of accurate three-dimensional method and speed-up ratio are as shown in Figure 9 for the three-dimensional visualization effect of accurate three-dimensional method.
The content not being described in detail in instructions of the present invention belongs to the known prior art of professional and technical personnel in the field.