23 results about "Near field scattering" patented technology

The invention provides a carrier concentration database establishing method, a carrier concentration testing method and a carrier concentration testing system.The carrier concentration database establishing method comprises the steps that theoretical models of a finite dipole model and a Deroude model are established, adjusting the effective length of the probe of the theoretical model and the ratio of the effective inductive charge to the total inductive charge to calculate a standard sample with known carrier concentration to obtain a plurality of pieces of first spectral information; detecting second spectral information of the standard sample by adopting a terahertz near-field detection device; fitting the first spectral information and the second spectral information to obtain an optimal fitting model corresponding to the current carrier concentration; and repeating the steps, and establishing the carrier concentration database. According to the invention, the near-field scattering signal and the interaction between the probe and the sample can be better represented, the error problem caused by only using the formula for calculation can be effectively overcome, and the calculation accuracy of the semiconductor carrier concentration can be further improved.

The invention provides a method and system for detecting electromagnetic compatibility efficiency of a wave-absorbing material and a storage medium, and relates to the technical field of electromagnetic compatibility efficiency detection. The method comprises the following steps: firstly, carrying out first electromagnetic measurement on a target area of the electronic equipment when a wave-absorbing material is not laid to obtain a first near-field scattering parameter set; and carrying out local minimum detection and amplitude and space distribution threshold presetting on the parameter set to screen out problem resonance frequency points. And laying the to-be-measured wave-absorbing material in the target area, and carrying out second electromagnetic measurement according to the same measurement condition to obtain a second near-field scattering parameter set. And comparing the two measurement data, calculating the local variable quantity, the space average suppression degree and the peak suppression ratio of each problem resonance frequency point, and constructing a comprehensive efficiency index on the basis of the local variable quantity, the space average suppression degree and the peak suppression ratio, thereby realizing quantitative evaluation on the overall efficiency and the local hot spot suppression capability of the wave-absorbing material. And finally, judging whether the electromagnetic compatibility efficiency of the material reaches the standard or not according to the space average suppression degree and the comprehensive efficiency index. Accurate evaluation of the electromagnetic compatibility efficiency of the wave-absorbing material is realized.

The invention belongs to the technical field of unmanned aerial vehicle millimeter wave communication channel modeling, and discloses an urban low-altitude unmanned aerial vehicle millimeter wave communication channel modeling method under sand and dust weather conditions. According to the method, a three-dimensional geometric random channel model is provided, and scatterers are divided into three types: near-field scatterers at the transmitting end and the receiving end adopt bicylindrical models, suspended dust adopts a complete ellipsoid model, and ground fixed scatterers adopt a lower half ellipsoid model with a larger semi-major axis. On the basis of the model, channel impulse response containing sight distance, primary scattering components and secondary scattering components is derived, and a space-time correlation function and Doppler power spectral density are calculated. And finally, establishing a joint path loss model: on the basis of the two-path fading model, introducing an additional attenuation factor related to the visibility of the sand and dust and the particle charge mass ratio, and determining specific parameters of the factor according to the grade of the sand and dust. According to the method, the channel characteristics can be accurately predicted, and theoretical support is provided for anti-interference design and link optimization of the millimeter wave communication system of the unmanned aerial vehicle.

The invention provides a method for determining a weighting coefficient of triple simulation of a distributed near-field scattering center, and relates to the technical field of scattering center radio frequency simulation. The method comprises the following steps: establishing a mathematical coordinate system by taking a turntable center point as a coordinate origin; determining a position vector of each point on the rectangular plane structure on the target based on the established mathematical coordinate system; based on the determined position vector of each point on the rectangular plane structure, determining the expression of a triple weighting coefficient of each point on the rectangular plane structure; and determining the triple weighting coefficient of the whole rectangular plane structure based on the determined expression of the triple weighting coefficient of each point on the rectangular plane structure. In this way, radio frequency simulation of the near-field distribution type scattering center can have higher precision and efficiency.

The invention discloses an improved near-far field data transformation method and device based on a transfer matrix, and belongs to the field of RCS testing and data processing. The method comprises the following steps: according to the maximum size of a to-be-measured target on a rotation plane and the distance from the center of a measurement antenna to the scattering center of the target, calculating to obtain a synthetic aperture angle required by transformation calculation; performing one-dimensional gridding division processing on the area where the target to be tested is located along the transverse direction, and respectively establishing a near-field test observation matrix and a far-field test observation matrix of the target to be tested in the grid area obtained by division; according to the near-field test observation matrix and the far-field test observation matrix, calculating to obtain a transfer matrix for converting near-field scattering characteristic data into far-field scattering characteristic data; and updating the transfer matrix according to a preset test frequency and a conversion processing center angle, and calculating to obtain all far field scattering characteristic data of the to-be-tested target. The method can effectively reduce the scale of the observation matrix and improve the calculation efficiency.

A method for modeling a three-dimensional scattering center using target bounce ray projection and simulating near-field echoes involves inputting a target CAD model and, in combination with near-field detector parameters, using multi-bounce ray tracing technology to obtain ray trajectories and exit aperture fields. The imaging space is divided according to resolution requirements, and the ray exit points are projected into three-dimensional space. All rays are superimposed to obtain the target's three-dimensional scattering center. A dynamic area search is performed on the target's three-dimensional scattering center model, combining the near-field detector's motion trajectory relative to the target and the antenna pattern, to obtain the scattering center in the area illuminated by the antenna's main beam. Near-field dynamic echoes are generated based on the near-field reconstruction formula for the point scattering center. This method avoids time-consuming integral operations, reducing the computational effort by orders of magnitude and making it suitable for calculating massive amounts of near-field scattering characteristic data from targets in short-range detection.

The present invention relates to a near-field and far-field data transformation method and device based on a transfer matrix. The method comprises the following steps: calculating the minimum synthetic aperture angle Φ required for near-field and far-field data transformation; performing grid processing on the target area; constructing a near-field observation matrix A N ; Construct far-field reconstruction matrix A F ; Based on the near-field observation matrix A N and the far-field reconstruction matrix A F Construct a transfer matrix A; realize the mapping of the target's near-field scattering characteristic data to the far-field scattering characteristic data through the transfer matrix A. The method of the present invention directly establishes the mapping relationship between the target's near-field and far-field scattering characteristics with the help of the transfer matrix concept, and can quickly and accurately transform the target's near-field scattering characteristic data to the far field.

This invention discloses a non-cooperative multi-user localization method in near-field scattering environments, comprising two stages: signal source acquisition and user identification. When the number of users and the transmitted pilot signals are unknown, the method leverages the system's inherent characteristics and machine learning algorithms to achieve multi-user localization in complex scattering environments. In the first stage, utilizing the spatial orthogonality between signals from different locations in the near field, a synchronous orthogonal matching pursuit algorithm based on a deep convolutional neural network (CNN) is used, with a stop iteration indication provided, to acquire the positions of all users and scattering points. In the second stage, a signal energy-assisted k-means clustering algorithm is used, simultaneously incorporating the distance between data points and signal energy information into the cluster center update criterion to accurately identify users. This invention effectively solves the problem of non-cooperative multi-user localization in near-field scattering environments.

The invention belongs to the field of electromagnetic scattering measurement and calculation, and provides a far-field RCS calculation method for cylindrical near-field scattering data hierarchical preprocessing and MoM inversion, which comprises the following steps of: firstly, obtaining an original cylindrical near-field scattering data matrix Eraw through cylindrical near-field scattering data measurement, then carrying out data hierarchical preprocessing on the original cylindrical near-field scattering data matrix Eraw, and finally, carrying out MoM inversion on the original cylindrical near-field scattering data matrix Eraw; the data layering preprocessing comprises system error calibration, background noise suppression and regularization-based probe compensation which are executed in sequence, and ideal field data Eideal are obtained; an excitation vector is obtained according to ideal field data Eideal projection, and surface current distribution J is obtained through current distribution inversion based on a moment method; and finally, according to the surface current distribution J, a far-field scattering field Es is calculated by using a radiation integral formula, and a far-field RCS value is calculated by combining the incident plane wave field intensity Ei. In conclusion, the method improves the data processing precision and the accuracy and efficiency of far-field RCS calculation through data hierarchical preprocessing and a precise inversion strategy.

The application belongs to the technical field of medical apparatus and instruments, and discloses a non-contact tumor cell in-vitro screening device and method, which comprises a wireless radio frequency probe built-in wideband radio frequency transceiver antenna unit, a multi-stage adjustable impedance matching network, a near-field coupling radiation structure and a radio frequency detection circuit, which are used for transmitting 1MHz-100GHz frequency band electromagnetic waves and synchronously receiving echo signals and near-field scattering signals; a signal processing system is connected with the wireless radio frequency probe and is used for pre-processing and feature extraction of the dual-mode signals; a control unit is internally provided with an AI fusion system, which is used for feature fusion analysis of the pre-processed dual-mode signals and outputs a benign and malignant determination result; the AI fusion system comprises an IC-CF-DMAS image reconstruction module, a one-dimensional convolutional neural network module, a cross-attention fusion module, a weighted voting decision module and a classification head, realizes deep interaction and accurate determination of cross-modal features, and realizes low cost, no radiation, rapidness, non-invasiveness, portability and high accuracy of early tumor screening.

The invention discloses an electromagnetic near-field scattering characteristic modeling calculation method based on half-space target source reconstruction and electronic equipment. The method comprises the following steps: modeling the ground into an infinite PEC, and constructing a surrounding surface for a target scatterer on the ground and a ground area in contact with the target scatterer; calculating an incident field of the incident wave on the surrounding surface, and solving equivalent electromagnetic current distribution on the surrounding surface by taking the incident field as an excitation source; removing a target scatterer in the surrounding surface, and performing integration on the equivalent electromagnetic current distribution by using a half-space green function to obtain a part of scattered field at the observation position; and calculating a background field of the observation position when only the incident field is incident on the infinite ideal electric conductor ground, and adding the background field and a part of the scattered field to obtain a total electromagnetic field of the observation point. Half-space target source reconstruction is carried out based on the Huygens equivalence principle, the model complexity is greatly reduced, the operation efficiency is remarkably improved, the problem of ground truncation is solved, and meanwhile, the method is suitable for far-field and near-field scenes.

The invention provides a method for determining the complex amplitude of a scattering center in target near-field scattering center modeling, and relates to the technical field of complex target scattering center modeling. The method comprises the following steps: establishing a mathematical coordinate system for a target; determining a position vector of each scattering center of the target based on the established mathematical coordinate system; determining a normalized near-field scattering field of each scattering center of the target in the observation area based on the determined position vector of each scattering center of the target; determining a normalized near-field scattered field of the target in the observation area; and determining the complex amplitude of each scattering center of the target according to the determined normalized near-field scattered field of each scattering center of the target in the observation area and the normalized near-field scattered field of the target in the observation area. Therefore, the total near-field scattering field of all the scattering centers on the near-field observation area can be maximally similar to the real near-field scattering field of the target, so that the scattering center amplitude can be quickly and accurately determined.

The invention relates to a method and device for simplifying large-scale simulation. The method comprises the steps that an analysis task for a target structure is obtained, and the target structure is subjected to structure division to obtain a plurality of substructures; determining a propagation space required for executing the analysis task according to the analysis task, and determining a plurality of first modes according to the size of the propagation space, wherein the plurality of first modes comprise a plurality of propagation modes and a plurality of evanescent modes; performing electromagnetic simulation of each substructure by using all first modes of the electromagnetic waves to obtain a substructure near-field scattering matrix of each substructure; and determining a target near-field scattering matrix of the target structure based on the near-field scattering matrixes of all the substructures. The near-field scattering matrix of the complete target structure is accurately predicted, the electromagnetic simulation process of the complex structure can be simplified in the mode that a large-scale simulation problem is divided into a plurality of small-scale simulation problems, the computing resource requirement of full-wave simulation is greatly reduced, and therefore the near-field characteristic analysis task of the complex structure is dealt with.

The invention discloses a non-cooperative multi-user positioning method in a near-field scattering environment, which comprises two stages of signal source acquisition and user identification, and realizes multi-user positioning in a complex scattering environment by means of mining of own characteristics of a system and a machine learning algorithm when the number of users is unknown and pilot signals are sent, and in the first stage, the number of users is not known, and the number of users is not known. The spatial orthogonality between signals from different positions in a near field is utilized, a synchronous orthogonal matching pursuit algorithm based on a deep convolutional neural network CNN is used, iteration stopping indication is provided, and the positions of all users and scattering points are obtained; and in the second stage, a k-means clustering algorithm assisted by signal energy is used, and the distance between data points and signal energy information are simultaneously incorporated into an updating criterion of a clustering center so as to accurately identify the user. According to the invention, the problem of non-cooperative multi-user positioning in a near-field scattering environment is effectively solved.

The invention provides an RCS near-field measurement method based on amplitude correction and phase recovery. The method comprises the following steps: initializing an RCS near-field measurement scene; acquiring correction parameters of an amplitude correction system; the amplitude correction system is used for correcting the near-field scattering amplitude of the to-be-measured target body and the calibration ball; near-field results of the to-be-measured target body and the calibration ball are calculated; recovering the near-field phase of the to-be-measured target body; and obtaining an RCS result of the to-be-measured target body. According to the invention, the near-field scattering amplitude of the to-be-measured target body and the calibration ball is corrected, and the near-field scattering measurement corrected amplitude of the to-be-measured target body is subjected to alternate mapping transformation, so that the near-field phase of the to-be-measured target body is recovered; the defect that accurate near-field phase data are difficult to obtain due to approximate distance terms and high measurement frequency in the prior art is overcome, the measurement accuracy is effectively improved, and meanwhile the test cost is reduced.

The invention discloses a sea surface scene low-altitude unmanned aerial vehicle millimeter wave communication channel modeling method. The method comprises the following steps: firstly, constructing a three-dimensional geometric random channel model, and dividing scatterers into three types: a double-sphere surface is used for collecting and sending near-field scatterers at two ends, a double-focus ellipsoid is used for describing high-humidity salt mist atmospheric particles, and a part of cylinders is used for simulating dynamic sea surface and spindrift scatterers; secondly, channel statistical characteristics are derived based on the model, the channel statistical characteristics comprise channel impulse response jointly formed by sight distance, primary and secondary scattering components, a space-time correlation function and Doppler power spectral density, and the scatterer angle obeys mixed probability distribution; and finally, constructing a path loss model: based on the two-path model, introducing an additional attenuation factor related to the salt mist concentration and the atmospheric humidity, and determining parameters of the additional attenuation factor according to the sea condition grade. The method fully adapts to the high-humidity salt fog environment and dynamic sea condition characteristics, can accurately characterize the channel space-time characteristics, and provides a theoretical basis for link planning and performance evaluation of a marine unmanned aerial vehicle millimeter wave communication system.

The present disclosure relates to a method and device for simplifying large-scale simulation, the method comprising obtaining an analysis task for a target structure and performing structure partitioning on the target structure to obtain a plurality of sub-structures; determining a propagation space required for performing the analysis task according to the analysis task, and determining a plurality of first modes according to the size of the propagation space, the plurality of first modes comprising a plurality of propagation modes and a plurality of evanescent modes; performing electromagnetic simulation on each sub-structure using all the first modes of electromagnetic waves to obtain a sub-structure near-field scattering matrix of each sub-structure; and determining a target near-field scattering matrix of the target structure based on all the sub-structure near-field scattering matrices. The present disclosure accurately predicts the near-field scattering matrix of the complete target structure, and this way of decomposing a large-scale simulation problem into a plurality of small-scale simulation problems can simplify the electromagnetic simulation process of complex structures, greatly reduce the computing resource requirements of full-wave simulation, and thus cope with the near-field characteristic analysis task of complex structures.

The invention provides an RCS near-far field transformation method and system based on synthetic aperture imaging, and belongs to the technical field of communication radars. A strict RCS (radar cross section) near-far field transformation algorithm is established by utilizing the progressive property of cylindrical wave expansion of a Hankel function in a cylindrical coordinate system and combining near-field scattering data, so that the problem of errors caused by wavefront curvature in near-field measurement is solved, and the echo signal intensity of a to-be-measured target under a far-field condition can be accurately obtained. Based on multi-angle radar signal fusion and splicing of near-far field transformation results, a high-resolution scattering characteristic image of a to-be-measured target can be synthesized. According to the method, the distance coupling effect in near-field measurement is eliminated while the detail features of the target are reserved, so that the electromagnetic scattering behavior of the target under the far-field condition is reflected more truly.

The near-field scattering characteristic test technology can be used for detecting the structure and internal composition of a large target (such as an airplane, a tank and a civil automobile), and has important application in the aspects of safety, production, transportation, test, detection and the like. The invention discloses a channel entrance non-cooperative large-target near-field scattering imaging diagnosis system in order to overcome the defects that in a traditional near-field scattering imaging diagnosis method, complete target cooperation is needed, and the testing process is complex. The system is composed of a multi-angle one-dimensional MIMO array antenna, an amplitude-phase regulation and control network, a radio frequency transceiver, a three-dimensional laser scanner and an upper computer, wherein the multi-angle one-dimensional MIMO array antenna is arranged on a four-wall frame of a channel entrance. The system performs full-angle electromagnetic wave irradiation on a moving non-cooperative target to obtain near-field scattering data of the target; obtaining the position and track information of the target through optical scanning point cloud imaging; and performing comprehensive processing on the near-field scattering data and the position track information of the target to obtain a near-field imaging result and performing diagnosis. The method has the advantages of convenience, low cost and high flexibility, and is expected to play an important role in non-cooperative target imaging diagnosis.

The application discloses a method for rapidly simulating three-dimensional scattered waves in a sound wave far detection transversely isotropic stratum, and belongs to the field of seismic wave forward simulation. The application is used to solve the technical problem that it is difficult to efficiently and universally simulate three-dimensional scattered waves in single well imaging of the transversely isotropic stratum in the prior art. The application comprises the following steps: obtaining parameters required for simulation; deriving an analytical solution of a sound source far field wave under a transversely isotropic medium according to a steepest descent integral method, and obtaining an incident wave field, wherein saddle points of quasi-SV waves and quasi-P waves are solved by using a Newton-Raphson method; establishing an elastic wave velocity-stress staggered grid, introducing the incident wave field into a calculation space boundary by using a total field / scattered field technology, and performing numerical simulation on a local region containing a scatterer to obtain a near field scattered wave field; calculating a virtual source wave field based on the analytical solution; and converting the near field scattered wave field and the virtual source wave field into a scattered wave field at a position of a well receiver based on a fluid-solid coupling reciprocity theorem. The application is suitable for a transversely isotropic medium with arbitrary parameters.

The invention relates to a near-field probe optimization method suitable for a terahertz nano-spectrum technology, and the method comprises the steps: employing a customized AFM probe, carrying out the experiment, combining with the analysis of full-wave electromagnetic simulation, and systematically exploring the regulation and control rule of the curvature radius of the tip of the probe on the imaging and wide-spectrum signals of a scattering type scanning near-field optical microscope working at 0.5-1.5 THz. The relation between the curvature radius R of the tip end of the probe and the intensity of the near-field scattering signal is determined and used for optimizing the near-field probe, and the near-field scattering signal with the wide frequency spectrum of 0.5-1.5 THz can be remarkably improved by optimizing the size of the tail end of the tip end of the AFM probe.

A method for measuring an optical property of a submicrometer region of a sample, comprising the following steps: a. Interacting a probe tip of a probe microscope with a region of the sample; b. Illuminating the sample with a light beam from at least one tunable source with a medium wavelength < λg such that light is scattered from the probe-sample interaction region, the scattered light comprising near-field light scattered from the probe tip and background scatter; c. Interfering a reference beam with the scattered light, the reference beam having an adjustable relative phase; d. Collecting at least some of the light resulting from the interference between the scattered light and the reference beam with a detector; e. Swiping across the relative phase to produce an interferogram; f.Comparing a property of the interferogram measured in the area of ​​the sample with a property of a reference interferogram to obtain a relative measurement of the scattered light; g. Repeating steps af at several medium wavelengths; and wherein an electric field strength of the reference beam is more than 20 times an electric field strength of the background scattered light.

The application provides an echo generation method based on an attribute scattering center near field correction model, containing the following steps: S1, inputting parameters of an attribute scattering center far field model; S2, correcting the far field scattering field amplitude and phase of the LSC based on the radar parameters in the near field, the position relationship between the LSC and the radar, and obtaining a local type scattering center near field correction model; S3, dividing the DSC into multiple segments, searching the segments and the observed regions of the DSC observed by the radar under each radar line of sight angle; S4, correcting the far field scattering field amplitude of the DSC through a step response function; S5, correcting the far field scattering field phase of the DSC under each radar line of sight angle, and obtaining a distributed type scattering center near field correction model in combination with the number of segments of the DSC observed; S6, generating the near field scattering echo of the target under the current radar position based on the attribute scattering center near field correction model, changing the radar position, and repeating S2 to S6.