最新刊期
卷 34 ， 期 9 ， 2006
- 摘要：This paper proposes a new speckle reduction method based on anisotropic diffusion and robust statistics for SAR speckle reduction.With the local statistics values of SAR images and robust staticstics,the method establishes a new diffusion coefficient,which provides anisotropic diffusion in the heterogenous area and isotropic diffusion in the homogeneous area.关键词：SAR;speckle;anisotropic diffusion2|1104|5更新时间：2025-07-16
- 摘要：This paper studied the optimizing technology based on the character of the DSP (Digital Signal Processing) and its data routeway,and proved that these optimizing technologies could improve the software’s efficiency from five times to fifteen times.High efficient programmer can make the system real-time,and it can reduce the cost of hardware,make the system simple and improve its reliability.To improve the software efficiency,this paper studied the removing relativity,intrinsic,short data processed as int data and software pipeline technologies,and these technologies are applied in the real-time image compression system based on C6416,with the inputting data rate 82M byte/s~110M byte/s and the outputting data rate 2.9M byte/s,the system achieved the goal of real-time processing.关键词：software pipeline;remove relativity;intrinsic;real-time processing2|931|4更新时间：2025-07-16
- 摘要：The algorithm based on spectrum shift estimation is a processing method with brief flowchart and less processing time for improving range resolution in distributed small satellite synthetic aperture radar(DSS-SAR).But its performance is decreased by spectrum overlap and estimation error of spectrum shift.The influence of these two factors on the algorithm is analyzed in this paper.The mathematic expressions of the combination image,including the effect of the two kinds of errors,are deduced respectively,and the image quality worsening caused by the errors is discussed.The expressions and the discussion show that spectrum overlap decreases the peak side lobe ratio and the integral side lobe ratio of point targets,and the error of spectrum shift attenuates main lobe and increases the side lobe of point targets in the combination image.The point target simulation is employed to validate the analysis.Some suggestions are presented to improve the implementation of the algorithm based on spectrum shift,and a new concept of processing depth is proposed to enhance the practicality of the algorithm.关键词：improvement of resolution;data processing;algorithms;error analysis2|961|0更新时间：2025-07-16
- 摘要：In bi/multi-static synthetic impulse and aperture ground-wave radar,multiple frequency-carrier signals are transmitted simultaneously by multiple antennas in the transmitting station.The returns of different carrier-frequency must be separated from one another before transmitting pattern is synthetically formed in the receiving station.Such a problem can be solved by adopting digital mixers and low-pass,but the amount of operation in this way is too large for real-time realization.Therefore,this paper presents the technique of channelized receiver based on multiphase filter bank.Compared with low-pass filter bank channelized receiver,the amount of operation of the multiphase filter bank receiver can be reduced by N2 (N is the number of channels).At last,the results of real-data processing with experimental system of the radar are given,which will verify the validity of this technique in such a radar system.关键词：synthetic impulse and aperture radar;ground-wave;bi/multi-static radar;channelized receiver;multiphase filter bank2|947|3更新时间：2025-07-16
- 摘要：In some satellite communications applications,we need to perform Direction of Arrival (DOA) angle estimation under the restriction that shorting of receivers when receiving and processing the signals impinged on an array antenna.In essence,this demands that using a limited number of receivers to process a large number of DOA signal.This paper proposes a method named Subarray synthesis based Direction of Arrival angle estimation.An equivalent output covariance matrix is firstly synthesized based on a given set of subarray antennas’ output covariance matrices;impinged signal’s DOA estimation is then performed based on the equivalent covariance matrix;Subarray optimization criterion and method are also discussed.Monte Carlo simulations verified the effectiveness of the estimation method.关键词：array signal processing;direction of arrival angle (DOA) estimation;subarray synthesis;time division multiplexing (TDM);eigenspace decomposition2|892|0更新时间：2025-07-16
- 摘要：In most of multifocus image fusion methods,the parameter configuration of fusion model is usually based on experience.In this paper,a new multiobjective optimization method of multifocus image fusion based on IMOPSO (Improved Multiobjective Particle Swarm Optimization) is presented,which can simplify the model of multifocus image fusion and overcome the limitations of traditional methods.First the proper evaluation indices of multifocus image fusion are given,then the uniform model of multifocus image fusion in DWT (Discrete Wavelet Transform) domain is constructed,in which the model parameters are selected as the decision variables,and finally IMOPSO is designed to optimize the decision variables.IMOPSO not only uses a mutation operator to avoid earlier convergence,but also uses a crowding operator to improve the distribution of nondominated solutions along the Pareto front,and uses a new adaptive inertia weight to raise the optimization capacities.Experiment results demonstrate that IMOPSO has a higher convergence speed and better search capacities,and that the method of multifocus image fusion based on IMOPSO achieves the Pareto optimal image fusion.关键词：multifocus image fusion;multiobjective optimization;improved multiobjective particle swarm optimization(IMOPSO);discrete wavelet transform (DWT)2|1172|3更新时间：2025-07-16
- 摘要：Mobile satellite network is a special time-varying network,and its QoS Routing problem is more complicated than the QoS Routing problem of current terrestrial networks.By exploiting the predictive nature of the mobile satellite topology and introducing the interrupting probability and the cost model of service,the influence on the QoS and network performance caused by the handover is described.Besides,a novel satellite network delay constraint minimum cost routing (SDCMCR) algorithm,which can obtain a path to satisfy the delay constraint as well as the minimization of influence caused by the handover,is proposed.This algorithm gives attention to the network performance of service interrupting and blocking.And at the same time,it has a low computing complexity to adapt to the restricted computing capability of satellite equipment.Correlative simulation indicates that this novel algorithm is superior to other current algorithm in respect of computing complexity,service blocking probability etc.关键词：satellite communication network;QoS Routing;delay constrained;routing algorithm2|1185|2更新时间：2025-07-16
- 摘要：For the reduction of sampling bandwidth,Inverse synthetic aperture radar (ISAR) echoes are usually dechirped first in the receiver.Then the dechirped signal employs FFT to get the range image in frequency domain.In general,the bandwidth of the target image is much less than that of the radar signals.So the narrowband signal can be used to modulate the receiving signal.Coherent jamming is proposed for jamming ISAR.Some video signals modulate the receiving signal in frequency domain,then the resulting signal is retransmitted.The dechirped output of the coherent jamming will produce cover jamming.Thus,ISAR can not obtain the range image.The paper also studies the effect of phase modulated jamming on the Doppler image.The coherent jamming can obtain some processing gain,so it can save jamming power.Theoretical analysis and computer simulation justify the validity and efficiency of this jamming technique.关键词：electronic countermeasures;dechirping;coherent jamming;inverse synthetic aperture radar2|978|13更新时间：2025-07-16
- 摘要：This paper concentrates on accurate motion compensation method for airborne SAR in diving model.The equivalent squint range model is deduced in the case of constant acceleration movement and CA-ECS (Constant Acceleration-Extended Chirp Scaling) imaging algorithm is proposed with new phase compensation factors based on this range model.The influences of multi-directional velocities and accelerations are taken into account in phase compensation factors of CA-ECS algorithm,so motion compensation with acceleration can be achieved via phase compensation.This algorithm is a more versatile and applicable imaging algorithm for subaperture data.The computer simulation results illustrate that the squint range model has less error and CA-ECS algorithm can be used to accomplish motion compensation with acceleration efficiently.关键词：SAR;imaging algorithm;constant acceleration-extended chirp scaling;equivalent squint range model;motion compensation2|1235|16更新时间：2025-07-16
- 摘要：This paper presents a time domain semi-analysis method based on the precise integration (PI) technique for solving Maxwell’s curl equations.Due to the introduction of the PI technique,the time domain method can not only eliminate the limitation of the stability condition for the time step size t ,but also make the numerical dispersion being independent of t .The finite difference schemes of the precise integration time domain (PITD) method are deduced in computational domain and on absorbing boundary,respectively,and the time domain recursion scheme is also deduced.Moreover,the resolving scheme of the invertible matrix problem involving the time domain iteration is presented.Practical calculation is carried out,and the results are compared with the ones of the analysis solution and finite difference time domain method.The results show that the PITD method is free from the restriction of the Courant-Frendrich-Levy stability condition.At the same time,the larger time step size will not deteriorate the numerical dispersion.关键词：precise integration time-domain (PITD) method;finite difference time-domain (FDTD) method;stability;numerical dispersion;resonator2|845|2更新时间：2025-07-16
- 摘要：Some basic principles of time domain electromagnetic field radiated by any kind of sources,especially by phased array antenna are presented. From the principles,we find the differences of radiating properties between time domain antennas and frequency domain antennas. And it is possible to describe the radiating properties of a time domain antenna using time domain signal distribution on a far field spherical face. The time domain electromagnetic fields of a ultra wide band ultra low side lobe phased array antenna have many new fashions,which are very difficult to be described in frequency domain. So it is very necessary to develop time domain methods to describe an ultra wide band ultra low side lobe phased array antenna.关键词：phased array antenna;time domain far field;time domain direction property2|938|4更新时间：2025-07-16
- 摘要：Dispersion characteristic of asymmetrical coplanar waveguide(ACPW)using finite-difference time-domain(FDTD)method is presented,a FDTD-model of ACPW is advanced,and the transient propagating waveforms along the ACPW,which are excited by retarded Gaussian pulse,are found in the time domain.After the time-domain field distributions are obtained,frequency-domain parameters such as characteristic impedance Z0 are calculated using Fourier transformations.The results agree well with available theoretical and experimental data over a wide frequency range.关键词：asymmetrical coplanar waveguide;finite-difference time-domain;murs absorbing boundary condition;characteristic impedance Z0;dispersion characteristic2|904|1更新时间：2025-07-16
- 摘要：The problems of maximum number of codewords for binary constant weight codes are studied by employing the theory of Johnson Schemes.In Delsarte's association schemes theory,Q-transform were introduced to study the distance distributions of binary constant weight codes.First,we study the Q-transforms of distance distributions of binary constant weight codes. Then,by using the properties of Q-transforms,we obtain a new upper bound of number of codewords for binary constant weight codes.This bound is similar to Grey-Rankin bound in error-correcting codes theory in form and improves previously known results in certain cases.关键词：binary constant weight codes;maximum number of codewords;distance distribution;Johnson schemes;Q-transform2|667|0更新时间：2025-07-16
- 摘要：With the growing use of Email,it is urgent to resolve the severe problem of Spam.Inspired by the self-protection mechanism of biological immune system,a multilevel Spam filtering algorithm is proposed.Experiments on the acquired immune layer have been presented and the results show that the algorithm can get high grade in recall,precision and accuracy of Spam filtering.It is also noted that better performance can be achieved by properly arranging the relations between the detector layers.关键词：artificial immune system;acquired immunity;spam;multilevel spam filtering2|1185|9更新时间：2025-07-16
- 摘要：Network congestion is caused by the unexpected burst.According to characteristic analysis of network traffic burst,the paper proposes a renovation method of congestion control algorithm(TCP-Shape) against the traditional congestion control algorithms,which uses dummy data segment probe to probe the available bandwidth in a TCP path and use flow shape techniques to make the flow look like more smoother.The experiments also show that the new congestion control algorithms can do better on data segment drop and throughout performance against the traditional congestion control algorithms.关键词：congestion control;available bandwidth measurement;flow shape technique;network measurement2|1086|3更新时间：2025-07-16
- 摘要：The leakage power issue is challenging high-performance microprocessor design,especially as feature size shrinks.Not only are low leakage technologies and circuits well researched,but also architectural control methods are studied hotly.Caches represent a sizable fraction of the total power consumption,so they need to be managed firstly.LRU is the most popular replacement algorithm used in set associative caches,but researches show that the latter blocks in LRU list are rarely accessed again.LRU-assist algorithm proposed in this paper exploits existing LRU information to expand the low leak portion in cache in addition to the time-based drowsy and decay mechanism.Simulation results show that the cache off ratio can be increased by 15% and leakage power is greatly saved with negligible performance overhead.关键词：microprocessor;cache power;leakage;LRU-assist2|908|6更新时间：2025-07-16
- 摘要：In CDMA system,a constrained least mean fourth (LMF) criterion is proposed to construct a multi-user detection algorithm.The criterion is proven to have global minima in AWGN environment,and these stationary points can all decorrelate the multiuser signal as expected.The algorithm is a higher-order statistics type approach.Furthermore,an adaptive multiuser detector is obtained by using the method of the steepest descent.The detector has the virtues of global convergence and low computational complexity.In AWGN channel and multiuser environment,the simulation is studied and its results further demonstrate theoretic conclusion.关键词：blind multiuser detection;least mean fourth;MAI;CDMA2|1048|1更新时间：2025-07-16
- 摘要：One image enhancement algorithm based on neighborhood limited empirical mode decomposition (NLEMD)is proposed.NLEMD is one novel time-frequency analysis tool which has the adaptive features of Huang’s EMD and meanwhile adopt neighborhood limited (max time-width) to overcome other EMD’s gray spots in images.The high frequency data is got using the ability of NLEMD,then we revise the remnants according to the illumination and the illumination contrast to adjust the whole illumination of the image.Experiments prove that the novel algorithm is efficient in image enhancement and better than current algorithms in detail achieving.关键词：empirical mode decomposition;local wave;image enhancement;intrinsic mode functions2|1287|8更新时间：2025-07-16
- 摘要：Target tracking of Over-the-Horizon-Radars (OTHR) inevitably faces the problem of multiple propagation modes,low detection probabilities,low measurement accuracy and low data-sampling rate.In this paper,a Multipath Viterbi Data Association (MVDA) algorithm is proposed,through modeling target movement in ground coordinate and implementing data association in radar coordinate so that Viterbi Data Association (VDA) is extended from association between measurement and track to association among measurement,propagation mode and track.The simulation results show that MVDA is superior to VDA and Multipath Probability Data Association (MPDA).关键词：sky-waves over-the-horizon radar;multipath Viterbi data association;target tracking2|1169|13更新时间：2025-07-16
- 摘要：A method to implement high-throughput network protocol decoder using hardware is proposed.Two technologies are used in this method:high speed parallel string match based on pipeline and high speed message validity check based on ABNF(Augmented Backus Naur Form).The performance of SIP(Session Initiation Protocol)protocol decoder implemented by this method is also valuated and the comparison with software implementation is made.It can be find out that the network protocol decoder implemented by this method can get an improvement up to tens of times while only relatively little hardware resource is needed and the throughput of the system can be improved dramatically.关键词：pipeline;Angmented Backus Naur Form(ABNF);string match;pattern match2|907|1更新时间：2025-07-16
- 摘要：This paper studies the principle and algorithm of profile clutter map,and analyzes the false alarm and detection probability of profile clutter map when the clutter is Rayleigh distribution;meanwhile,under some given system parameters,the affection of the number of scans,iterative coefficients and the affection of average clutter-to-noise rate (CNR) to detection probability under different false alarm rate are studied,thereby,it provides some theoretical support for the forming of profile clutter map in low clutter-to-noise ratio.关键词：profile clutter map;clutter map;clutter;clutter’s amplitude map;Rayleigh distribution2|937|0更新时间：2025-07-16
- 摘要：Detector noise and scale-factor errors exist in all of photoelectric equipments,especially in guided munitions which use strap-down detectors and integral form of proportional navigation law,the effects of noise and scale-factor are part of the reasons for miss distance.The effects of noise and scale-factor errors on the system are studied in this paper and some valuable conclusions are obtained.These conclusions will have a great significance for engineering applications.关键词：white noise;scale-factor error;strap-down detector;Integral form of proportional navigation guidance law2|1019|5更新时间：2025-07-16
- 摘要：On the base of research on real-time transport protocol and real-time transport control protocol (RTP/RTCP),a flow control algorithm is proposed by introducing synthesis prediction,and variable increase and decrease are used to adjust sending rate adaptively.Finally,the experiments are carried out to illustrate that the algorithm can enhance the stabilization of RTP flow,decrease the jitter,and utilize network bandwidth efficiently.关键词：RTP/RTCP;synthesis prediction;adaptive flow control2|2091|5更新时间：2025-07-16
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Fast Acquirement of Vehicle Targets from High-Resolution SAR Images Based on Combining Multi-Feature
摘要：A method for fast acquirement of vehicle targets from high-resolution SAR images is proposed.At first,a constant false alarm rata (CFAR) detector is utilized to locate the potential target regions.Then size,shape,and contrast features of each potential region are computed for target discrimination,and false alarms created by nature clutter and partial man-made clutter are rejected by combining these features to make determination based on voting decision.The experiment results show the proposed method is effective.关键词：synthetic aperture radar;vehicle target;detection;discrimination2|910|9更新时间：2025-07-16 - 摘要：The echoes of meter-wave radar received are coherent signals consisted of direct and reflected signals due to the multipath effect at low elevation angles.A new method that can estimate the DOA (direction-of-arrival) of a target under low-angle condition is presented in this paper.Linear transform is applied to measured data firstly.Difference operation is performed to measured data and transformed data secondly.Finally applying super-resolution algorithm to the result from step two,we can obtain the DOA of a target for meter-wave radar at low altitude.This method is not sensitive to the signals environments and can overcome multipath effect effectively.Theoretical analysis and simulation results demonstrate the merits of the new algorithm.关键词：coherent signals;direction-of-arrival;reflection coefficient;low altitude2|1000|16更新时间：2025-07-16
- 摘要：In image formation of large-squint and large-beamwidth SAR,a high coupling and range-variant migration echo must be processed so that it is difficult to get a fine focusing synthetic aperture radar (SAR) image.In this paper,we first compared about the source and degree of the coupling in those two models by the mathematical two-dimension spectrum expression of SAR echoes.Next,we mainly discuss the method of uncoupling in the nonlinear chirp-scaling algorithm and attain a relation of residual coupling and two parameters,which is mapping slant-range width and most far slant-range distance.Finally,we give the difference of those two parameters when that algorithm is used to large-squint and large-beam width SAR image formation.关键词：SAR image formation;two-dimension spectrum coupling;nonlinear chirp-scaling algorithm2|1070|16更新时间：2025-07-16
- 摘要：The performance analysis of a kind equalization algorithm based on Fourier Transform for radar channel is carried out.The factors including Signal-to-noise ratio,relationship between bandwidth and sampling rate and group delay affecting the algorithm’s performance are analyzed and solutions are proposed.According to the principle of circular convolution,a method of realizing non-causal equalizer is proposed to suppress the influence of the group delay effect.All analysis is based on experiment data.The results show that the modified algorithm could achieve good performance after avoiding the influence of the several factors.关键词：channel equalization;group delay;sidelobe cancellation2|1181|17更新时间：2025-07-16
- 摘要：This paper constructs combined orbit determination (COD) models from the angle of range-sum observation data by analyzing Low Earth Orbiter (LEO) combined orbit determination ranging mode based on Bi-satellite Positioning System (BPS).and designs a ranging system error parameters estimation method and a numerical fusion method based COD algorithm.Simulation computation results show that COD strategy can restrain influence of geostationary orbit satellites ephemeris errors,and LEO orbit determination precision can achieve 11.26 meters which is estimated by two days range sum simulation data,which proves the validity of the system error estimation method and numerical fusion algorithm.2|984|4更新时间：2025-07-16
- 摘要：A genetic-algorithm-based AMC structure,which is made up of high-impedance frequency selective surface,is introduced.The aperture-coupled microstrip antenna using this structure has 10dB less back radiation and 2~3dB more gains than a conventional one.This structure has important reference value to the manufacture of antenna.Practical antenna is fabricated,and the measured results basically agree with the simulated well.关键词：genetic algorithm;artificial magnetic conductor (AMC);high-impedance frequency selective surface (HZ-FSS);aperture-coupled microstrip antenna2|1099|3更新时间：2025-07-16
- 摘要：The synchronization performance of OFDM system based on fractional Fourier transform is studied.The influences of the carrier frequency offset,sample frequency offset and timing misalignment in the OFDM system with fractional Fourier transform are discussed and compared with traditional OFDM system with normal IFFT/FFT.Simulation results show that the OFDM system based on fractional Fourier transform with appropriate parameter has better synchronization performance when carrier frequency offset is discussed.2|814|2更新时间：2025-07-16
- 摘要：The complex Alternation Theorem proposed by L.J.Karam and McClellan is the foundation of the complex Remez algorithm for Chebyshev design of complex FIR filters. Herein,the complex Alternation Theorem is extended to the case with inequality constraints,and then a new algorithm is presented for the design of Chebyshev FIR filters with magnitude inequality constraints. The new algorithm combines the complex Remez algorithm and the iterative Remez algorithm proposed by X.P. Lai,and is guaranteed to converge to the optimal solution,if exists. A lot of design examples are to be given,and the results of simulation illustrate the performance of the algorithm关键词：complex FIR filter;constrained complex Alternation Theorem;complex Remez algorithm;iterative Remez algorithm;constrained complex Remez algorithm3|960|4更新时间：2025-07-16
- 摘要：A method was presented to accelerate the MOT arithmetic using method of moment in time domain EFIE.Using a moving time window in the MOT method,to eliminate the iterative calculation which has no contribution to the present time step,in this way,accelerate effect was obtained.The simulation results were the same as to the conventional MOT method,which proved that it is an effective method.关键词：time-domain method of moment;electric field integral equation;time-window2|808|0更新时间：2025-07-16
- 摘要：A three-dimensional finite-difference time-domain (FDTD) parallel algorithm for an anisotropic media (ANI-FDTD parallel algorithm) is presented,with dyadic permittivity and permeability on a distributed network by using the message passing module.According to the FDTD formulation of anisotropic medium,28 nodes are involved when the electric or magnetic field component at one node is calculated.The FDTD iterative computation at each sub-domain can be progressing successfully providing the field component values of interrelated nodes near the sub-domain interface communicate appropriately.The distribution of 28 related nodes is indicated and the way of message passing for field components between sub-domains in ANI-FDTD parallel computing are analyzed in details.The numerical results show the feasibility of presented scheme.关键词：anisotropic medium;dyadic permittivity and permeability;parallel algorithm;finite-difference time-domain (FDTD) method2|1006|2更新时间：2025-07-16
- 摘要：HFSS(High Frequency Structure Simulator) was used to calculate the S parameter of the different structural microwave chemistry reactor made of rectangular waveguide resonator,while changing the structure dimension of the microwave chemistry reactor such as shape and dimensions of iris,diameter of reaction tube and thickness of reaction tube wall,material and positions of reaction tube.The optimal simulating results were consistent with experimental results and the optimal structure dimensions of the microwave chemistry reactor were given.The positions of the reaction tube and the plunger affected the distribution of electromagnetic field in microwave chemistry reactor,and hence it directly affected the work of the microwave chemistry reactor.In the optimal structure reactor,where the positions of the reaction tube and the plunger were 106mm and 146mm respectively,the methane in reaction tube were positioned at the strongest and uniform electric intensity,which made it easier for the methane obtain enough microwave power to discharge.The simulating results were consistent with our experimental results.关键词：microwave chemistry;microwave chemistry reactor made of rectangular waveguide resonator;HFSS soft2|1157|7更新时间：2025-07-16
- 摘要：The periodic boundary condition in the three-dimensional (3-D) electromagnetic computer code CST MWS is used to the computational simulation for high-frequency characteristics of helical slow-wave circuit.Validated by the analytical method of tape helix model and the experimental data,the agreement is excellent.The computer code CST MWS and tape helix model are also used in this analysis to determine the effect on dispersion and on-axis interaction impedance of the wedge support rod and T-shaped support rod geometry parameter variations.The results show that the phase velocity and interaction impedance will decrease across the bandwidth while the angle of the wedge support rod and the width of T-shape support rod’s narrow end increase,and increase while the height of T-shaped support rod’s narrow part is longer.关键词：CST MWS;tape helix model;dispersion;interaction impedance;periodic boundary conditions2|1211|0更新时间：2025-07-16
- 摘要：According to the general coupled-wave equations of wave-guide with helical corrugation,Based on rules of mode coupling in helical wave-guide,the coupled equation of the helical wave-guide for backward-wave and the formuale for dispersion are obtained,the dispersion characteristics and the working principles for the gyrotron backward-wave oscillator are analyzed.Based on coupled-wave equations,the field distributions for wave-guide with helical corrugation in eigenmode are also given.关键词：the wave-guide with helical corrugation;coupled equations;backward-wave;dispersion characteristics;eigenmode2|1016|2更新时间：2025-07-16
- 摘要：What causes relativistic magnetron to have much lower efficiency than common magnetron? Based on the residual energy of electron stream at the anode,different factors affecting the relativistic magnetron’s efficiency,including synchronous velocity,gyral movement,depth of Brillouin flow,Lamour radius,DC space charge field and RF field,were analyzed.Comparing those factors in the typical A6 magnetron’s parameter,result shows that the intense RF field is the primary reason to lower relativistic magnetron’s efficiency.This conclusion was proved by the PIC simulation,too.关键词：high power microwave;relativistic magnetron;electronic efficiency;residual energy2|1095|1更新时间：2025-07-16
- 摘要：A novel fast optimal design method based on genetic algorithm (GA)is given for the rectangular waveguide slotted array."Approaching ideal current" cost function is present in this optimal method instead of the "Approaching ideal pattern" cost function in conventional method,considering the mutual coupling in the waveguide slotted array in the Elliott equations.The results of 4-slot array show the validity of this method,the array of 8-slot is also analyzed.Examples show that this method is much more quick than conventional method based on "Approaching ideal pattern" optimization,and this method can be used to the large array design.关键词：slotted array antenna;genetic algorithm;optimization2|1309|2更新时间：2025-07-16
- 摘要：Based on the per unit area second-order cross section spectrum of the ocean proposed by Howell,a new algorithm to extract ocean wave information from HF radar backscatter by a narrow-beam antenna system is presented,in which the integral object is changed and the integral range is divided asymmetrically.Numerical simulation is performed under condition of different SNR and sea state.The simulation result shows that this algorithm has preferable precision under SNR higher than 35dB.As a further test of this algorithm,comparison are made between wave height estimates obtained from wave instrument and a HF ground wave radar at 7.7MHz,using data collected during "The HF ground radar field contrast test".The average absolute error of the significant wave height is 0.32m,which demonstrates the basic accuracy and feasibility of the inversion algorithm.关键词：high frequency ground wave radar;second-order cross section equation;non-direction wave height spectrum;sparse matrix;significant wave height2|853|0更新时间：2025-07-16
- 摘要：We study the different formulations of the hybrid vector FEM/BEM (Finite Element Method/Boundary Element Method) for 3-D scattering.It is shown that the condition number of matrices from different hybrid formulations varies greatly with different BEM formulations used,and therefore,the stability of the hybrid formulations varies correspondingly.Issues of combined testing function method and single testing function method for BEM are also discussed.We show that the combined testing function method can be viewed as the single testing function method.And the accuracy of the results obtained by the two methods is compared,which rectified the conclusion that accurate results can be obtained by the hybrid method only when the combined testing function method is employed.Based on the reliability,accuracy,and ability to immune to the corruption of interior resonance,the formulation of hybrid vector FEM/BEM for 3-D scattering is recommended.关键词：finite element method;boundary element method;hybrid method;electromagnetic scattering2|870|2更新时间：2025-07-16
- 摘要：The Contrast optimization algorithm is a magnitude-based autofocus algorithm.The contrast optimization algorithm is described as an optimization model via which the local optimal solution can be achieved.Two optimization methods,Golden section and Fibonacci series,are employed to deal with this optimization model according to features of practical SAR(Synthetic Aperture Radar) systems.Efficiency of the contrast optimization algorithm is greatly improved compared with the quondam methods due to the application of the model and the two methods which are mentioned above.关键词：synthetic aperture radar(SAR);contrast optimization;autofocus2|1004|7更新时间：2025-07-16
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