最新刊期
卷 29 ， 期 12 ， 2001
- 摘要：The influence of the envelope of pulse radar signal on the intermediate frequency sampling is investigated,especially the influence of non-ideal envelope on mirror frequency rejection is studied,and the main influences of mirror frequency and amplitude loss are pointed out.As a special case,the effect of rectangular-envelope-edge of pulse signal on intermediate frequency sampling is carefully studied.The influence of different parameters on mirror frequency rejection is analyzed to ensure the pulse edge character after intermediate frequency sampling and to reduce mirror frequency as much as possible.Moreover,the influence of mirror frequency rejection of intermediate frequency sampling is researched for linear modulated frequency pulse signal.关键词：pulse radar;intermediate frequency sampling;mirror frequency rejection;envelope;parameter2|1269|2更新时间：2025-07-16
- 摘要：A combined scheme of smart antenna and PIC with low complexity is proposed for the uplink receiving of WCDMA system.At first we develop the LS-DRMTA algorithm proposed by Z.Rong into a new algorithm named pilot bit assisted LMS-DRMTA in accordance with the uplink frame structure of WCDMA system.The proposed algorithm cuts down lots of computation complexity of LS-DRMTA algorithm,which simplifies its application in WCDMA system.Further more,the simulation experiments indicate that the new algorithm can perform at much lower BER than LS-DRMTA.After the array processing of the received signal by the proposed algorithm,we go further to cancel the CCI by adaptive PIC which is a useful method for MUD.The overall scheme proposed is characterized by low computation complexity、little delay and easy real time implemetation.关键词：WCDMA;uplink;frame structure;smart antenna;pilot bit;adaptive PIC2|1948|0更新时间：2025-07-16
- 摘要：As a new spotlight SAR image formation algorithm,Frequency Scaling approach precisely performs the range cell migration correction without interpolation by using a novel frequency scaling operation.A new Frequency scaling image formation algorithm suitable for high squint angle is proposed in this paper.Point target simulations up to 45 deg squint angle have been carried out to show the validity of the improved algorithm.Also presented is a spotlight image extracted from stripmap raw data of DLR's E-SAR system.关键词：synthetic aperture radar;spotlight mode;imaging algorithm2|2053|3更新时间：2025-07-16
- 摘要：Such kind of signal-selectivity algorithms in solving the problem of estimating time difference of arrival(TDOA) of radio waves,such as CCC method,has been developed to some extent by W.A.Gardner.But unfortunately,the methods mentioned above are not suitable for the cases when the echo signal from moving targets has nonzero Doppler shift,since the cycle frequency of echo signal varies with time.To solve the problem of estimating the TDOA of the FM signal with nonzero Doppler shift,a more generalized approach,which is referred to as the extended CCC(ECCC) method,is introduced in this paper.By utilizing the detection method of cell averaging constant false alarm rate(CA-CFAR),the estimates of TDOA and Doppler shift can thus be determined by the peak position over the two-dimensional space of TDOA and Doppler shift.In addition,it can be seen in this paper that the class of algorithms developed by W.A.Gardner is just a special case,corresponding to zero Doppler shifts.Computer simulations are also performed on the given method and simulation results have shown that the novel method works more efficiently in highly corruptive environment than the conventional correlation methods do.关键词：FM signals;moving targets;time-difference-of-arrival extraction;spectral correlation2|821|5更新时间：2025-07-16
- 摘要：The preconditioned conjugate gradient method(PCG) for solving triple Toeplitz linear systems is put forward and is combined with the fast Fourier transform(FFT).The combining algorithm,called PCGFFT,is applied to RCS analysis of large dipole-array antennas.Because of the preconditioner,the condition number of the coefficient matrix is largely improved.The numerical results show that PCGFFT reduces the need for computer memory,speeds the iteration and enhances the convergence.关键词：dipole-array antenna;radar cross-section;preconditioned conjugate gradient method2|1527|0更新时间：2025-07-16
- 摘要：A new method for estimating spatial narrow-band signal directions of arrival in the presence of colored noise with unknown covariance is presented.An estimate of the noise covariance matrix is given.The data for parameter estimation is then prewhitened using the estimated noise covariance,hence,overcoming the highly biased estimates.Its performances are confirmed by computer simulations.关键词：array signal processing;colored noise;DOA estimate2|1940|11更新时间：2025-07-16
- 摘要：Based on the active absolute calibration of airborne radar,clutter characteristics of typical terrain (plain,hill,mountain and compound terrain) are measured at L-band HH polarization.Effects of the airplane postures on antenna pattern are modified.Analysis results of constant γ models,exponent model and four probability distributions are compared with data.It shows that γ model with index n and Weibull distribution,K distribution agree with the measured data and their statistical fitting parameters are also given.关键词：airborne radar;model;probability distribution;terrain;clutter2|985|1更新时间：2025-07-16
- 摘要：With the analysis of polarimetric measurement error model,a novel correction algorithm on radar target's reciprocity is presented based on least degradation rule.After transforming the nonlinear optimal problem of four degrees of freedom with constraints to a nonlinear optimal problem of two degrees of freedom without constraints,the solution is given.Simulation results verify its feasibility and indicate its good performance.关键词：polarization scattering matrix;correction on reciprocity;least degradation correction algorithm2|992|2更新时间：2025-07-16
- 摘要：A new method named Probability Cycle Analysis is proposed in this paper,which is used to analyze the performance of self-organized time division multiple access (S-TDMA) datalink system.By defining system state entropy,duration of slot state and state steady probabilities are stated,and an evaluation method on channel throughput adopting ratio of the true value of safe state to state entropy of system is presented in this paper.A terminal coverage partition model based on Co-Channel Interference (CCI) rule is also provided,which is used to analyze specifically the effect of hidden terminals in different areas.Finally,a solution to hidden terminals problem based on piggy frame technology is proposed.Simulation results show that the method is effective.关键词：very high frequency datalink;time division multiple access;Markov chain;hidden terminals2|1035|2更新时间：2025-07-16
- 摘要：Target detection of high-resolution polarization radar has been discussed in this paper.Signal to Clutter Ratio (SCR) is a determinate factor in radar detection.A cascaded detection scheme is presented.The enhancement of SCR at each stage results in the ultimate improvement of detection performance.At first,by exploiting the polarization information,the fused and enhanced one-dimension range profile is obtained.Then the problem of target detection is converted to that of scattering points detection.Finally,simulation results show that the ultimate performance of target detection is improved significantly.关键词：high resolution;polarization;one-dimension range profile;polarization whitening filter;Target Detection2|832|2更新时间：2025-07-16
- 摘要：In a WDM transport network,internal dependence of lightpaths could lead to the critical status that the failure of a physical fiber leaves the virtual topology unconnected.This may make the restoration of service by the higher level networks using the WDM network (such as SDH,ATM or IP) impossible.It is necessary to avoid the above cases while embedding virtual topology into physical topology.Existent Disjoint Alternate Path (DAP) algorithm always assumes that all network nodes have full-range wavelength conversion capability.A new heuristic algorithm,called Virtual Topology Mapping for Design Protection Based on Layered Graph (LG -VTMDP),used in design protection for WDM optical networks is proposed in this paper.The algorithm considers two problems of routing and wavelength assignment simultaneously.Load balancing and capacity constraints of physical links are also considered.The LG-VTMDP algorithm is shown to perform better than the combination of the DAP algorithm and existent wavelength assignment algorithms.Based on the result of the LG-VTMDP algorithm,an efficient Wavelength Converter Placement (WCP) algorithm is presented subsequently.关键词：WDM network;survivability;design protection;wavelength converter placement2|945|0更新时间：2025-07-16
- 摘要：Routing and Wavelength Assignment(RWA) in WDM optical transmission networks is a very important problem.A new RWA strategy is proposed for dynamic Routing and Wavelength Assignment problem in WDM optical transmission networks.Simulation shows these RWA algorithms perform better than some existing ones,which can make full use of networks' resource with lower networks' blocking.关键词：WDM;OXC;routing;wavelength-assignment;rerouting;resource assignment strategies2|1689|2更新时间：2025-07-16
- 摘要：Chip-level partitioning technology is used for solving the problems coming from the physical design of Opto-electronic multichip module(OE MCMs):heat dissipation,system speed,and maximum optic interconnect distance.The physical models and algorithms for OE MCM partitioning is given.This paper uses genetic algorithms (Gas) for opto-electronic system partitioning and improving the genetic algorithm.The modified algorithm is more suitable for OE MCM partitioning than standard Gas,and it can decrease the power consumption about 50%.关键词：opto-electronic MCM;OE MCM partition;module;genetic algorithms(Gas)3|972|0更新时间：2025-07-16
- 摘要：A new formula,which is based on δ-gap and probe sources,to calculate the antenna input impedance using the FDTD method is derived from Yee's difference equation.It is very simple and efficient,and reduces the errors of antenna impedance at the low frequencies near zero.The method makes it easy to calculate antenna input impedance.To check the validity of such method,a monopole antenna on a box is simulated using FDTD,and the result shows that the errors of antenna impedance at the low frequencies disappear.A patch antenna fed by coaxial line is also calculated,and result has a good agreement with that by another software.关键词：FDTD;antenna impedance;monopole antenna impedance;microstrip antenna impedance2|1486|1更新时间：2025-07-16
- 摘要：In this paper, we propose a QoS(Quality-of-Service)-guaranteed multipath routing policy in MPLS(Multiple protocol label Switching) networks. The key idea is traffic dispersion throughout the network, so that the load of the network can be balanced and call admission ratio is increased while user-required QoS being guaranteed. We first discuss the decomposition and allocation issues of end-to-end QoS constraints on paths. Based on these analyses, we present the traffic dispersion path selection strategy used by multipath routing,and also investigate the critical parameter K's effect on the performance of above path selection strategy. Numerical results show the effectiveness of multipath routing in traffic dispersion, load balancing, and call-admission-ratio improvement. We also conclude that the advantage of using multipath routing becomes more obvious as the users' requests for network resources get stricter.关键词：MPLS;QoS-guarantees;multipath routing;traffic dispersion2|1189|5更新时间：2025-07-16
- 摘要：The domain decomposition FDTD method (DD-FDTD) is presented for solving complex problems and improving the accuracy of solutions.Based on this idea,the original domain is decomposed into several sub-domains according to the features of the problem.In each sub-domain,the conformal meshes are created in local coordinates and the FDTD computation is carried out independently in local meshes and local time step,and there is no stability concern.In the iteration procedure of FDTD,the data are exchanged between adjacent sub-domains with overlapped meshes.A suitable data-exchanging scheme proposed here integrates the sub-domains and leads to a more exact solution.This greatly increased the calculation efficiency.A 2-D scattering problem is calculated by using this method and the accuracy of the solution validates the usefulness and exactness of this method.关键词：domain decomposition;time-domain finite-difference;conformal meshes;2-D scattering2|1644|3更新时间：2025-07-16
- 摘要：Two kinds of the coupled finite element-new-type equivalent source method are systematically illustrated.The coupling of the two methods (FEM and NESM) can enhance the advantages of both techniques and help to overcome their specific weaknesses.The methods are especially adapted to the calculation of open domain problems including nonlinear,anisotropic and stratified media.关键词：FEM;new-type equivalent source method;coupled method;nonlinear magnetostatic field2|795|0更新时间：2025-07-16
- 摘要：The advantages of placement wavelength converters only in some nodes of WDM Mesh-Torus are studied in this paper.The performance of binomial distributed placement and uniform placement in terms of blocking probability,conversion gain and fairness are evaluated and compared under non-Poisson traffic mode,and it is proved that the uniform placement is an optimal scheme in mesh-torus when link loads are uniform.关键词：wavelength division multiplexing;partial virtual wavelength path;blocking probability;conversion gain;fairness2|793|0更新时间：2025-07-16
- 摘要：In the Internet Age,Email is one of the fastest and the most economical methods of communication.the large number of emails,by which people communicate with each other nowadays,are usually classified by the filters,which use the regular classifier based on keyword-compared.However,this traditional method has some shortcomings,such as lack of flexibility,incapability of describing the compilcated problims summarily and effectively.Therefore,its effectiveness if not very satisfactory.This paper introduces the knowledge of machine learning on the base of the traditional regular classification.A new intelligent email classifier is desinged to solve the summary classified problems well and demonstrate the feasibility of the system through experiments.关键词：email;classify;expert system;machine learning2|1621|1更新时间：2025-07-16
- 摘要：Robustness is one of the major issues of digital watermarking algorithms.An effective method to improve the robustness of watermark is to embed the watermark adaptively based on the human visual system and signal characteristics.In this paper,an adaptive video watermarking algorithm in wavelet domain is proposed.According to the properties of the 2-D wavelet coefficients,the watermark is inserted into the coefficients of LL subband to achieve better robustness performance.In order to enhance the strength of the components of the watermark,we propose to classify the wavelet coeffcents based on the motion of the objects and the texture complexity of the contents in the video sequence.According to the result of classification,the strength of the watermark components is adjusted adaptively.Meanwhile,the transparency of watermark is guaranteed.The experiemental results show that the proposed watermarking algorithm is robust to video degradation and distortions,e.g.,those that result from additive Gaussian noise,MPEG-2 coding at high compression-ratio,temporal downsampling and spatial downsampling.关键词：digital watermarking;video watermarking;wavelet transform;adaptive;robustness2|1272|7更新时间：2025-07-16
- 摘要：Some iterative frequency-domain deconvolution filters applied to modern time-domain measurement and metrology successfully are presented at first,such as Guillaume-Nahman deconvolution filter,optimal compensation deconvolution filter and synthetic deconvolution filter;Multiparameter optimization reason of iterative frequenay doman deconvolution filter is presented specifically and formula is deduced necessarily.The more reasonable expression of transmission function of deconvolution filter is given.And then,computer simulations for these deconvolution filters are performed and the waveform figures are given to compare the filtering effect of each deconvoltuion filter with the initialization.Finally,performance of these filters is cvaluated and compared and the result illustrates that multiparameter dcconvolution filter is the best one in waveform and variance.关键词：deconvolution filter;multiparameter optimization;performance evaluation2|993|1更新时间：2025-07-16
- 摘要：In electromagnetic compatibility (EMC) analysis,generalized resonance existing in multiple conductors open system is noticeable problem.The analysis of generalized resonance occurring in scattering by multiple conductors is presented utilizing moment method.The resonance is explained by generalized resonance cavity theory.关键词：generalized resonance;EMC;generalized resonance cavity2|1136|0更新时间：2025-07-16
- 摘要：A new method of multiresolution time-domain analysis is proposed,which is based on Coifman compactly supported scaling functions with some number of vanishing moments.The highly linear dispersional properties of the method are investigated and compared with conventional FDTD method.The problem of scattering from two-dimensional conducting cylinders is analyzed in order to demonstrate the advantages of this method over conventional FDTD scheme with respect to memory requirements and execution time.关键词：multiresolution time-domain analysis;Coifman scaling functions;finite-difference time-domain method2|938|3更新时间：2025-07-16
- 摘要：A method for efficiently implementing 2D image rotations on distributed memory parallel machines,is proposed in this paper.The method has been developed in the context of developing the algorithms in terms of high level abstractions.With newly developed notations based on a 2-pass rotation technique,we show that the parallel image rotation can be expressed concisely and performed effectively on distributed memory parallel architectures.Error analysis has been done for the 2-pass operations,and compensation schemes suggested to reduce noises.关键词：parallel image rotations;image processing abstractions;2-pass rotations2|1048|0更新时间：2025-07-16
- 摘要：A silicon microchannel array and continuum dynode was prepared by processes of Multiplex Inductively Coupled Plasma (ICP) and LPCVD respectively to form a silicon microchannel plate (Si-MCP) with 15 μm of through-hole diameters,16.8 of aspect ratio,and 110 of electron gain at 400V of working voltage.The microchannel topography,dimension effects and electron gain coefficient were analyzed and discussed.In new preparation of MCP,the matrix and dynode materials selections of the new microchannel plates was independent,and no effects existed between their forming processes.By comparing the electron gain of the prepared silicon microchannel plate with conventional one,we found the electron gain of Si-MCP was larger than glass MCP.Though there were some problems to be solved in the manufacture of electron multiplier of Si-MCP,it was expected that Si-MCP would be a new approach to enhance the performances of MCP and the quality of image devices.关键词：silicon;microchannel plate;aspect ratio;dynode2|1575|5更新时间：2025-07-16
- 摘要：In this paper,the affects of the match Fourier transform on moise are discussed,Theoretical analyses and simulations indicate that the match Fourier transform can enlarge the bandwidth of the coloured noise and compress the bandwidth of the matched signal,which improves the performance of detecting signal.Because the distribution of signal and noise is dissimilar in the different match Fourier field,so the filter can be made in the different match Fourier field to get better performance.The simulations show that under the condition of S/N=-20dB,if the chirp signal is filtered time after time in the different match Fourier field,the signal may be over 15dB more than noise.关键词：the match Fourier transform;chirp signal;coloured noise;filter2|937|5更新时间：2025-07-16
- 摘要：A neural network approach for redundancy VLSI/WSI arrays reconfiguration on Hopfield network is proposed on the basis of contradiction graph of fault element.Then the problem of arrays reconfiguration is translated into the independent set of contradiction and the dependent number equals to the number of nonspare faulty PE's.Thus the problem of arrays reconfiguration is solved.The experimental results show that the neural network method based on the graph model is an effective algorithm compared with heuristics algorithm.关键词：VLSI/WSI array;contradiction graph;independent set;Hopfield network2|873|1更新时间：2025-07-16
- 摘要：Probe errors analysis and correction are the key technique in time-domain near field measurement.We deduced the transform formulas of probe receiving character error function between different coordinate systems;used `time-window' to get rid of the multi-reflection wave,and presented the selection principle of `time-window'.Numerical results illustrated the efficiency of the new ways.关键词：receiving character error;coordinate transform;probe-compensation;time-window2|1250|1更新时间：2025-07-16
- 摘要：As an effective method to provide copyright protection for digital media,digital watermarking has drawn extensive attention recently.The paper proposes a new scheme of digital image watermarking based on the combination of discrete wavelet transform and discrete cosine transform.The experimental results demonstrate its better unification between the watermarking robustness and watermarking invisibility.Compared to the other image watermarking schemes,the watermarking with the proposed scheme is much robust against noise interference and commonly used image processing technique under the condition of same watermarking image quality.关键词：image watermarking;DWT;DCT;robustness2|1316|10更新时间：2025-07-16
- 摘要：In this paper,a multi-focus image fusion algorithm is proposed which takes features of human vision system (HVS) into account.First,registered original images are divided into several blocks.Then contrast error of every block is calculated considering contrast masking sensitivity.Finally,the contrast errors of corresponding blocks are compared to decode which should be used to construct the fused image.The influences of two parameters,size of decomposed block and threshold,on fusion performance are discussed.Experimental results show that the proposed method can operate real time.To stringent registered multifocus images,the proposed algorithm can achieve equivalent or superior performance to the algorithm based on wavelet decomposition.关键词：image fusion;contrast masking sensitivity;human vision system;wavelet transform2|1473|28更新时间：2025-07-16
- 摘要：The fundamental principle of W band narrow pulse-near distance radar is introduced.The function and distance of the radar are presented.The parameters including acceptance,segregation and the modulated cycle are analyzed.The leak in radio frequency,intermediate frequency and the transmission distortion of the nanosecond grade pulse are discussed.The overcoming method of that is given.Based on analysis,a W band narrow pulse solid radar are designed.FPGA measure distance system is adopted in this radar first.This method of distance measurement not only is convenient in debugging,but also can achieve high precision.Finally,the test result of this radar is given.关键词：millimeter;near distance radar;pulse;Measurement2|1250|2更新时间：2025-07-16
- 摘要：In this paper,a new Chaotic Pulse Position and Phase Coded Pulse Compression Radar (CPPPC-PCR) signal is studied.The Average Ambiguity Function (AAF) of CPPPC-PCR signal is investigated,especially a new method based on the Fourier Transform for deduction is proposed.Theory and simulation results show that this new radar signal possesses high range-velocity resolution,and at the same time it owns excellent low probability of interception and anti-jamming capability.关键词：chaotic sequence;pulse compression radar signal;average ambiguity function;pulse position and phase modulation2|1026|3更新时间：2025-07-16
- 摘要：In this paper,a new detection algorithm based on multi-frame detection technology for dim point moving target from image sequence was proposed.The algorithm first forms a composite frame,which is constructed by adding a few of difference images,and then detects target using pixel statistics.Compared with other algorithms,the new proposed algorithm in this paper is not only very fast,but has better performance.Theoretical analysis of the algorithm's performance and experimental results are also showed in this paper.关键词：dim point target;moving target;image sequence;multi-frame detection;statistic detection2|922|15更新时间：2025-07-16
- 摘要：Electromagnetic Compatibility problem of antenna system in airborne nacelle jammer is studied in this paper.Many methods used in computational electromagnetics,such as Spectral-Domain Approach etc,are applied in the predicting analysis and the design of antenna system.It is shown by experimental test that performance of the receiving and transmitting antenna system in airborne nacelle jammer is up to,or even surpasses the target designed.关键词：coaxial multi-mode horn of two chokes;radome;isolation;directional pattern;transmimssion coefficient2|1186|0更新时间：2025-07-16
- 摘要：This paper proposes a new mathematical model and an algorithm of availability of SDH fiber optic systems. Numerical solution of the model is discussed along with an illustrative example. The paper also analyzes the relationships between system availability and related parameters in detail and presents several ways to improve system availability.关键词：availability;survivability;fiber optic systems;SDH (SONET)2|1274|4更新时间：2025-07-16
- 摘要：The discrete from of match Fourier transform is introduced in this paper.This paper discusses the difference of the discrete match Fourier transform and match Fourier transform and the effect of sample on the discrete match Fourier transform.The analysis and computer simulation demonstrate that if the sample frequency is lower than the LFM signal width,the signal may be separated.关键词：sample;match Fourier transform;LFM2|904|6更新时间：2025-07-16
- 摘要：In this paper,an adaptive region search strategy and its performance are studied. Firstly,the optimal search performance is derived,and the relationship between the optimal search performance and the uniform search performance is presented. Next,the influence of the target distribution density's estimation error on the optimal region search performance is analyzed. Finally,adaptive search methods and their optimal parameters and their performance in stationary and nonstationary target distribution environment are investigated.关键词：phased array radar;region search;adaptive;performance analysis2|1169|6更新时间：2025-07-16
- 摘要：Photonic bandgap structures constructed with dielectric materials have been studied in this paper.FDTD method is adopted to excute the numerical simulation.The scattering characteristics of one and two dimension all dielectric PBG structures have been computed,including different incident angles.The reflection coefficients have been given.关键词：photonic bandgap structures;reflection coefficients;FDTD2|1278|1更新时间：2025-07-16
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