最新刊期
卷 30 ， 期 3 ， 2002
- 摘要：In the HF ground-wave OTH radar,the movement of the radar brings about the spreading of the first order Bragg lines.It is difficult to pick up and measure the ship targets of the cover-up in the spread first order Bragg lines for the shipboard environment.In this paper,the causation of the spread spectrum are firstly analyzed,then it is suggested to use single null beam to pick up the ship targets and use pair null beam to detect targets direction.At last the method is simulated and the validity of detecting method of targets direction is attested for the HF ground-wave OTH radar.关键词：OTH radar;antenna;target detecting0|881|0更新时间：2025-07-16
- 摘要：Genetic algorithms(GAs),one of the global maximum method,was firstly used to the elementary optimization of the amplitude of the slots in the rectangular slotted waveguide array,which simplify the design procedure greatly.Secondly,GAs,combined with the dynamic mutual coupling among all the slots were applied to optimize the offsets and the resonant lengths of the slots,which were the key factors of the antenna arrays.The results of the small array show the the validity of this method,the array of medium size (72 elements) array is also analyzed,and the same method can be extended to the large array design.关键词：slotted waveguide antenna array;genetic algorithm;optimization0|1088|4更新时间：2025-07-16
- 摘要：The global magnetic force distribution of single moving electron is firstly obtained by means of spherical cap harmonic analysis.In order to reduce the geomagnetic effect on the color picture tube and improve the image quality of the color picture tube,a kind of equipment that can practicably and effectively shield geomagnetic field is put forward in this paper.A new scheme that combines this new equipment with oscillation-method is put forward to more effectively improve the shielding efficiency also.Besides,comparing the shielding result of this new equipment with that of the current shielding style,it is shown that the new equipment is effective and practicable.The geomagnetic tolerance of the color picture tube can be loosened to a large degree after this equipment is used.The achievement in this paper can be applied to the manufacture of the color picture tube.Moreover,it has the practical value to reduce the production cost and increase the benefit.关键词：geomagnetic field;color picture tube;effect;equipment;shield;geomagnetic tolerance0|797|0更新时间：2025-07-16
- 摘要：We enhance the FDTD method for simulating transient EM surveys of underground objects,in which impulse excitations are laid on the ground surface and the electromotive force (EMF) is measured along the ground surface.In the late time of impulse excitation,the displacement current can be neglected because of slow variation.The diffusion characteristic dominates the electromagnetic process under ground.In order to apply the FDTD method to treat the underground problem,we introduce an artificial displacement current term in the diffusion equation.Examples given demonstrate the efficiency of presented scheme.关键词：finite-difference time-domain (FDTD) method;underground targets;transient EMscattering0|925|0更新时间：2025-07-16
- 摘要：A new classical small perturbation method of electromagnetic scattering from rough surface with consideration of the effect of the curvature of the surface is presented.The problem of scattering error due to this method at a grazing angle is solved.Comparing with a set of measured data,numerical computations of the backscattering radar cross section for actual natural rough surface by the classical and new small perturbation methods are given.The results show that the new small perturbation method is validity for the small,moderate and grazing angle incidence.关键词：the effect of the curvature;rough surface;electromagnetic scattering;small perturbation method0|1065|0更新时间：2025-07-16
- 摘要：In this paper linearly constrained minimum variance (LMCV) algorithm is originally applied to pattern synthesis for satellite multiple-beam antenna.Under constraint on main lobe level,the pattern of antenna is synthesized by minimizing the radiation power of antenna.Unlike conventional iterative algorithms,LCMV is an analytic algorithm,which makes it more accurate and efficient than those conventional algorithms and easily converge.In the end,through two representative examples,synthesis of pattern for square area and China mainland,LCMV proves to be superior to conventional iterative algorithms.关键词：satellite communication;multiple-beam antenna;pattern synthesis0|1334|8更新时间：2025-07-16
- 摘要：An algorithm is raised to deal with waveguide step discontinuity problems by using various new basis functions in the expansion of the fields at the discontinuity to solve the scattering parameters.The electromagnetic field's edge condition in the vicinity of metal wedges is generally taken into account and modified trigonometric functions are constructed as basis functions to expand the electromagnetic fields at the discontinuity.Matching the tangential fields over the common aperture can form a set of linear equations.Very good numerical convergence is observed.Furthermore,some different basis functions are constructed and evaluated,and the excellent convergence property is also obtained.For one discontinuity,the order of the linear equations is the same as the number (a few or only one) of the basis functions.This keeps the equations at the lowest order and the numerical computation efficiency is thus improved drastically.关键词：electromagnetic edge condition;waveguide discontinuity;numerical convergence0|896|2更新时间：2025-07-16
- 摘要：This paper applied prominent points’ information based on multi-PPP to compensate specific phase errors in spotlight SAR imaging.Among these points,the first one removes the phase errors from relative translation and produces a new focusing center,the second one is used to transform the rotational motion from unevenly to evenly,and the third one estimates the corresponding azimuth scaling factor.After this compensation,not only the space-invariant phase errors but also the space-variant phase errors are removed and high-resolution SAR images can be produced.It’s also analyzed that in PPP the second point can’t be processed independently of the third point in order to correct precisely motion errors from spotlight SAR images with PFA.How to select the prominent points so as to improve PPP is also suggested in the paper.At last the method is proved to be feasible by the simulation results when PPP autofocus is embedded in spotlight SAR imaging with PFA.关键词：spotlight SAR;motion errors compensation;multi-PPP;PFA0|785|0更新时间：2025-07-16
- 摘要：According to the features of airborne SAR moving target echoes,a new SAR moving target detection technique based on cross Wigner-Ville distribution (XWVD) is proposed.Its detection performs on condition that single target and multiple targets exist respectively.The experiment validates that the performance of this new method can detect the signal with very low SNR.It is better than the common method based on Wigner-Ville distribution.To eliminate the effects of cross-terms,according to the idea of elimination one by one,a new detection scheme of XWVD is proposed,which can detect small target embedded in some large targets.The simulation results prove its effectivity.关键词：synthetic aperture radar;moving target detection;cross Wigner-Ville distribution0|1190|8更新时间：2025-07-16
- 摘要：A new type matrix-virtual cumulant-based DOA matrix,is formed based on three arbitrary sensor subarrays with special translation.The azimuth and elevation of the incident sources can be estimated respectively from the amplitude and phase information of the eigenvalues of the new matrix.Accurate estimation can be obtained due to the arbitrary geometry of the subarrays and the insensitivity of cumulants to Gaussian noise.关键词：direction of arrival estimation;cumulant;virtual cumulant-based DOA matrix0|1006|5更新时间：2025-07-16
- 摘要：A definition of a logarithm bispectra-averaged is first given,followed by its three properties involving target recognition.Then a relationship is established between the logarithm bispectra-averaged and a high-resolution range profile.Thereupon,a distance criterion for automatic target recognition by logarithm bispectra-averaged and its implementation are suggested.Computer simulation with the acquired outfield data shows that the logarithm bispectra-averaged method applies to airplane recognition,and is effective and practical.关键词：radar signal processing;automatic target recognition;high-resolution range profile;logarithm bispectra-averaged method;simulation0|966|1更新时间：2025-07-16
- 摘要：Enhancing the resolution of SAR image can improve ATR significantly.An extrapolation algorithm is used to expand the 2-D bandwidth of the detailed image to enhance the resolution and the implementation steps are discussed in detail in this paper.The simulation results proves its validity.0|1690|7更新时间：2025-07-16
- 摘要：A method to implement multi-scale symmetry transform in the wavelet coefficients domain decomposed by using anti-symmetrical biorthogonal wavelets (ASBW) is presented with application to location of feature points on human face image.Compared to the original symmetry transform,which is performed on a single resolution level,our method can yield results with higher location accuracy without increment of computational burden.In addition,if an image is compressed based on ASBW decomposition,then our method provides a way to extract image features in compressed data domain without need of completely reconstructing the image.This is one of the most important technical consideration in the content-based indexing (CBI) problem.关键词：symmetry transform;location of feature points;anti-symmetrical biorthogonal wavelets;content-based indexing0|1300|10更新时间：2025-07-16
- 摘要：This paper presents a new volume rendering acceleration algorithm for semi-transparent volume objects.The volume rendering pipeline processor VGE provides full support for the popular ray casting acceleration techniques such as adaptive-ray-termination and space-leaping,thus it achieves frame rate up to 70Hz.Nevertheless,such high frame rates can only be achieved in the case that the volume elements are mapped either opaque or transparent.The new acceleration algorithm is designed to relax the dependence of the frame rate on the selected opacity mapping functions.The new algorithm uses an adaptive resampling strategy to replace the equidistant resampling,hence the time complexity is reduced and the memory bandwidth requirement is lowered.Experimental results show that the new algorithm can accelerate the rendering of semi-transparent volume objects by up to 4.7 times.Like space-leaping,the new algorithm needs to encode the adaptive sampling interval in a preprocessing stage.The preprocessing can be implemented in less than 30 seconds for volume data with 8 million voxels by heuristic algorithmic optimizations.关键词：direct volume rendering;visualization;algorithm;adaptive;distance coding0|1084|2更新时间：2025-07-16
- 摘要：The man-made cyclostationary signals have been widely used in many fields,such as signal detection,parameters estimation and beam forming etc.,because of its special property of cyclostationarity and periodicity.An effective algorithm referred to as the SC-SSF method has been developed by G.H.Xu to estimate direction of arrival (DOA) of radio waves impinging on the sensor arrays.But it is inconvenient to be put into practice in many practical applications,due to the difficulty in determining the size of the data matrix.To solve such a problem,a solution is introduced in this paper in detail.It analyzes the disadvantage of SC-SSF algorithm at first.And then a more general array signal model is obtained by passing the spectral autocorrelation function through a specifically designed filter.Thus a new DOA estimation method based on the new array signal model is developed as generalized SC-SSF (GSC-SSF),which utilizes MUSIC or ESPRIT algorithm to accomplish the DOA estimation.With the simulation,the new method proves to be more convenient and effective than SC-SSF in suppressing noises and forming the data matrix (or called the covariance matrix).关键词：cyclostationarity;direction-of-arrival estimation;SC-SSF algorithm0|1037|9更新时间：2025-07-16
- 摘要：The concept of optimizing the field pattern of a given equally spaced array by thinning process represents a very challenging problem with considerable practical advantages.In this paper,a properly modified genetic algorithm (GA) is applied at the first time to design a low sidelobe hexagonal planar array by thinning process.A study of the frequency characteristics of the thinned hexagonal planar array is made,and a new method,which has less computational work and is especially useful for large antenna arrays,is proposed for performance improvement of antenna arrays by thinning partially the array.The results show that the performance of the hexagonal planar array could be greatly improved by thinning,the maximum relative sidelobe level was reduced by 7.5~9.4dB,and thinning partially the array could attain the same performance as that of fully thinning.关键词：genetic algorithms;antenna arrays;thinned arrays0|1588|3更新时间：2025-07-16
- 摘要：K Singhal & J Vlach's NILT(Numerical Inversion of Laplace Transform) method is an efficient approach to the transient analysis of lossy transmission lines terminated with linear loads.This technique is utilized in this paper to derive a discrete-time model for transmission lines.The model thus obtained can be easily implemented in general circuit simulators,so that the transient simulation for arbitrary loaded transmission lines can be readily accomplished.Unlike the prevailing frequency domain methods employing the moment-matching technique,no rational approximation is required in this method and numerical problems thus aroused such as stability and preserving of the passivity are avoided.Both uniform and nonuniform lines are dealt with.Numerical experiments carried out by implementing the model into the circuit simulator SPICE have been performed and the results demonstrate the validity and efficiency of the method.关键词：transmission line analysis;VLSI interconnects;NILT0|1036|9更新时间：2025-07-16
- 摘要：This paper studies the movement estimation of the high resolution radar signal with additional Gaussian color noise.Movement between the missile and the target has notable influence on the range profile.The stepped frequency echo has polynomial phase,and the influence of velocity and acceleration was expressed as the second the third phase.Cyclostationary method is not sensitive to the Gaussian color noise and can do with non-Gaussian color noise as well,which is proved to be effective in low SNR environment.In this paper,the cyclostationary method is used to estimate the movement parameters from the phase in low SNR environment and to get ideal range profile as the result.关键词：high resolution;cyclostationary;Gaussian color noise0|953|7更新时间：2025-07-16
- 摘要：In this paper,the propagating modes of the asymmetrically supported broadside-coupled coplanar waveguide are analyzed with the quasi-static method.The correct criteria for C and π mode are given.The mistakes in the presented papers are corrected.The correct and complete formulas of voltage ratios,current ratios on two lines,effective dielectric constants and mode impedance for C and π mode are given.For the structure where dielectric medium in the upper layer is air and the dielectric medium in the lower layer is quartz or duroid,the curves of the effective dielectric constants and mode impedance for C and π mode are presented respectively.These results could be used as references for the analysis and design of this kind of circuits in three-dimensional (multilayer) microwave integrated circuits.关键词：propagating mode;asymmetric supported;broadside-coupled;coplanar waveguide0|1031|1更新时间：2025-07-16
- 摘要：The basic concept,principle and importance of sensor management are summarized,and the methods are analyzed and synthesized.Then,the essential characteristic and the future study problems of development of sensor management methods are presented.Finally,the closed loop control scheme of data fusion system is proposed,which consists of sensor subsystem,data fusion subsystem,decision support subsystem and sensor management subsystem.关键词：data fusion;sensor management;information theory;programming theory0|2052|26更新时间：2025-07-16
- 摘要：In the Internet,there are two types of QoS architectures: IntServ/RSVP and DiffServ.The DiffServ is divided into absolute DiffServ and relative DiffServ.First,the model of proportional differentiated service (PDS),a typical relative DiffServ model,and its two-implementation algorithms BPR (Backlog-Proportional Rate) and WTP (Waiting-Time Priority) are presented in this paper.Then,the performance of WFQ (Weight Fair Queuing),a typical PFQ (Packet Fair Queuing) algorithm,is analyzed and simulated.The result shows that WFQ has certain resistibility to the burst of higher priority traffic classes.WFQ has better resistibility under medium load than in heavy load,and the larger the ratio of weights of successive queues,the stronger the resistibility of WFQ.Finally,a new measurement-based WFQ (M-WFQ) is proposed.The performances of long-term and short-term of M-WFQ with BPR,WTP,and WFQ are given.The results show that M-WFQ has the best performance under normal traffic distribution reasonably and can be adaptive to variation of traffic load distribution.关键词：QoS;PDS;WFQ;measurement-based WFQ0|1020|2更新时间：2025-07-16
- 摘要：A FM-CW ground base C-band scatterometer is used to measure the bare soil surface.The measurement was conducted at different incident angles and for two soil moisture conditions.In-situ measurement is also arranged simultaneously in order to verify the retrieved moisture.During the moisture retrieval,the integration equation method (IEM) is used.The results show that the method could be used to build up the soil moisture database and could then be used for satellite data applications.关键词：retrieval;backscattering coefficient;IEM model;soil moisture0|1321|5更新时间：2025-07-16
- 摘要：The monolithic fuzzy neural networks model is considered.The contrasts are showed between the monolithic fuzzy neural networks and the traditional neural networks on the perceptron convergence theorem.Some issues are discussed on the perceptron convergence theorem of monolithic fuzzy neural networks.Two improving methods are investigated,which are presented as two modified perceptron convergence theorems,and the corresponding arguments or explanations support these modifications.关键词：fuzzy;neural networks;perceptron;learning algorithm;monolithic fuzzy neural networks0|920|2更新时间：2025-07-16
- 摘要：In millimeter-wave,the frequency drift of oscillators is very large,and phase-locked oscillators are often used,which make the cost of communication system very high.In this paper,a low cost W-band frequency tracing transceiver system is presented,which is used for digital communication.The data of tests indicate that,for 8448kbit/s,the threshold level is only 3dB higher than that of the millimeter-wave systems,in which phase-locked oscillators are used.At the same time,the scheme of this system is simple and the cost is low.The tests also show that the phase-locked loop has no obvious influence on the digital signal.关键词：millimeter wave;phase-locked;digital communication;frequency tracing0|1104|0更新时间：2025-07-16
- 摘要：A numerical technique employing the MOM and MEC is presented to study the scattering from slots antenna fed by waveguides with arbitrary terminations,and the frequency response and the RCS are obtained numerically.The rule to determine the number of the base functions is given in detail.It's shown the effect of the waveguides on scattering can not be neglected.By comparing the numerical results with experimental data,the applicability and the validity of the method are established and the errors of numerical results are analyzed.关键词：EM scattering;waveguide-fed slots antenna;Mom;MEC0|1016|2更新时间：2025-07-16
- 摘要：In this paper,the transmitted waveforms of a Gaussian pulsed light with or without initial chirp at different distances in a singlemode fiber are calculated,and the transmission characteristics are analyzed through time-window,frequency-window,and time-frequency plane of the Wigner-Vill distribution by using time-frequency analysis.Time-frequency analysis can provide more information about the dispersion and energy changes on the pulsed light transmission through the singlemode fiber.关键词：singlemode fiber;pulsed light;time-frequency analysis0|1270|1更新时间：2025-07-16
- 摘要：Multiwavelet possesses such very important properties in signal processing as orthogonality,symmetry,and short support,which makes up for the shortcoming of scalar wavelet,and takes on broader application prospects.This paper,from the aspect of filtering,mainly analyzes and designs multiwavelet filter.The processing method for multiwavelet coefficients is also presented in the paper.The simulation indicates the advantages of multiwavelet.关键词：multiresolution analysis;multiwavelet;filtering;denoising0|1295|3更新时间：2025-07-16
- 摘要：In this paper,one scheme has been proposed for controllable digital frequency generator in the AFC loop of a receiver.DDS technique is used here.The algorithm and architecture for the VLSI implementation of this digital frequency generator are discussed.Finally,simulations of performance and analysis are given.关键词：DDS;fully-digitalized receiver;phase truncation;frequency control word0|1137|0更新时间：2025-07-16
- 摘要：For high frequency electromagnetic wave(2~30MHZ),it is very difficult to calculate radiant and transmittal characteristics of antenna located in complex environment.With the development of high frequency technology,the problems need to be solved imminently.In this paper,finite difference time domain method is used to calculate this problem.First the radiant characteristics of the monopole located on lossy ground are calculated.Then the characteristics of the electromagnetic wave transmitted by antenna located near coast passing a section of lossy ground are analyzed,and the characteristics of far electromagnetic strength related to the length of lossy ground are given.The surface impedance is used in this paper,that reduces calculation amount and memory space to a very marked degree.关键词：finite difference time domain;surface impendence;high frequency antenna;high frequency electromagnetic wave0|791|0更新时间：2025-07-16
- 摘要：In this paper,a new moment method using helical segments is presented to model Normal Mode Helical Antenna (NMHA).Using this method,the NMHA can be modeled by a few segments.The current distributions and radiation patterns of some NMHAs are calculated.A comparison is made between results obtained using this helical segment algorithm and the linear segment algorithm,and the results of the two algorithms agree fairly well.When calculating the impedance matrix Z ,all the elements of the matrix can be obtained by only calculating a few elements with the application of the symmetric and periodic characteristics of the NMHA.Therefore,the CPU time and the memory storage are significantly reduced,with the accuracy and speed enhanced.关键词：method of moment;helical segment;normal mode helical antenna(NMHA)1|1396|3更新时间：2025-07-16
- 摘要：Ray_tracing is an efficient method to analyze the propagation prediction in urban microcell.But most papers about this method only treat about the direct algorithms,only a few papers treat about the inverse algorithms.This paper discusses in detail the inverse algorithm based on ray_tracing method,and builds up a tracing model of municipal microcellular region.关键词：ray_tracing;direct algorithms;inverse algorithms0|1503|8更新时间：2025-07-16
- 摘要：In this paper the characteristic of several typical HF radar waveforms are synthetically analyzed and compared.A new waveform with interrupted spectra is presented to improve the narrow continuous bandwidth usable in heavily congested electromagnetic environments.By cutting off the interference spectrum based on the result of the electromagnetic environment surveying system,HF radar could make use of the fractional silent spectra.This would greatly improve the radar's anti-jamming ability and effective bandwidth.Moreover,an improved adaptive targets echo reconstruction algorithm is used.Simulation results show that it could successively suppress the high sidelobe with this waveform.关键词：waveform design;sidelobe suppression;interrupted spectra;signal processing0|1427|8更新时间：2025-07-16
- 摘要：The effect of PMD (Polarization Mode Dispersion) to high-speed optic communication system has drawn more and more attention nowadays,and the measurement of PMD is of much importance.ITU-T G.650 Recommendation has recommended several approaches to measure PMD and the Jones Matrix Eigenanalysis Method is regarded as the chief one.Using Jones Matrix Eigenanalysis Method,we can get the most comprehensive information about optic fiber’s PMD,and this method has very high precision and broad measurement range.The principle of Jones Matrix Eigenanalysis Method for measuring PMD is illustrated in this paper,and an automated measuring system based on it is introduced,with some experimental results.Instead of using a polarimeter recommended in G.650,we use a polarizer controlled by a step-up motor to measure Jones optic Vector in this system,which is much cheaper.关键词：PMD;measurement;Jones vector;Jones matrix0|1614|0更新时间：2025-07-16
- 摘要：The application of photonic bandgap structures (PBG) as substrates in microstrip circuits has been investigated.The characteristic of stopband and effect to microstrip circuits are introduced.Novel cascade and hybrid parallel PBG structures based on ground defected structures are presented as inner microwave broadband filters.Experiments have been done and the frequency transmission characteristic is measured.Existence of the frequency bandgap and feasibility to construct microwave broadband filters have been proved.关键词：photonic bandgap structures;microstrip circuits;filters0|1045|2更新时间：2025-07-16
- 摘要：A conventional single-user-type detector is known to have an irreducible error floor and cannot handle the near-far problem in CDMA cellular communications.Recently,a series of maximum-SINR blind space-time CDMA RAKE receivers designed to tackle the near-far problem have been proposed.However,the interference suppression performances of these algorithms suffer from great degradation caused by the interference covariance matrix containing desired signals,which is called self-interference in this paper.This work proposes a novel self-interference cancellation technique to enhance their interference rejection capability.Simulation results demonstrate that the proposed technique offers high performance.关键词：space-time processing;blind detection;CDMA receiver0|880|0更新时间：2025-07-16
- 摘要：Microwave radiometer,as a passive remote sensing instrument,has broad application potential.However,these were limited by its spatial resolution given by its physical antenna aperture size.A synthetic aperture technology employing interferometry principle with complex correlators has been considered as a new type of instrument to give improved spatial resolution.In this paper,the authors analyzed the properties of a 1-bit digital correlator.The signal to noise performance has also been given to the systems that use this technology.Preliminary tests of such a system shows that it is a considerable technology to improve the system characteristic using the traditional analog complex correlators.关键词：microwave radiometer;interferometry;digital correlator0|989|3更新时间：2025-07-16
- 摘要：In this article we present a Monte Carlo simulation based method to calculate electron beam dose distribution in radiotherapy,for MC method is good at solving particles tranport issue.A MC code,LISTMC,has been developed based on EGS4 and PENELOPE to accomplish the task.In dealing with the inhomogeneous tissue and the complex geometry of human body,its results are more accurate than the methods used in practice.To reduce the lengthy computation time we used some techniques,such as reducing the limitation of boundary of voxel to the path of electron and code optimization etc.In many cases a good coincidence has been observed between EGS4 and LISTMC,but the computation time of LISTMC for 6 MeV electron beams is only 1/10 of EGS4-PRESTA.关键词：Monte Carlo method;dose calculation;radiotherapy;electron beam0|1336|1更新时间：2025-07-16
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