最新刊期
卷 37 ， 期 9 ， 2009
- 摘要：In air-to-ground synthetic aperture radar (SAR) surveillance,it is desirable to be able to detect slow moving targets within strong ground clutter.At present,using eigen-decomposition to the sample covariance matrix,three detection metrics (second eigenvalue,interferometric phase,similarity) can be acquired,which provides a new approach of detecting the slow ground moving targets.The paper aims at the theoretical shortages of the similarity and second eigenvalue.Firstly,according to diagonalizing matrix corresponding to a point on the upper-half of the unit sphere if the Pauli spin matrices are chosen as basis vectors,the paper revises the expression of similarity detection metric.Secondly,the paper originally puts forward and proves a proposition,which is the second eigenvalue’s validity tightly associated to the adjacent average processing to the sample covariance matrix.The two conclusions effectively reinforce the theoretical system of eigen-decomposition detection metrics.The simulated results prove the correctness of the conclusions.关键词：synthetic aperture radar (SAR);similarity;second eigenvalue;adjacent average0|2|0更新时间：2025-07-02
- 摘要：Considering statistic characteristics of synthetic aperture radar (SAR) images,a novel basis named complex bandelet (CB) was presented and applied on SAR image speckle reduction.The CB has characteristics of good shift-invariance,multi-directionality and self-adaptively approximate optimal matching.Cost function of CB searching optimization was constructed based on total variation (TV).And then generalized cross validation (GCV) was introduced to get asymptotic optimal thresholds without estimating noise variance.Numerical tests show that CB-based filter provided improvements both in visual effects and quantitative analysis,which are embodied in smoothness of uniform fields,continuity and clearness of geometric structure information simultaneously.The compared filters are classical spatial domain filters,wavelet transform-based filter,dual-tree complex wavelet transform-based filter,and bandelet transform-based filter.关键词：complex bandelets;total variation;generalized cross validation;SAR;speckle reduction0|2|1更新时间：2025-07-02
- 摘要：In ISAR imaging model, targets should move smoothly during coherent integration time(CIT).Since CIT is quite long,the fluctuation of target’s velocity and gesture will deteriorate imaging quality.Combining MIMO technique and ISAR imaging theory,this paper presents a MIMO-ISAR imaging method.By using a special M-transmitter N-receiver linear array,a group of M orthogonal PCM signals with identical bandwidth and center frequency is transmitted.With a matched filter set,every target response corresponding to the orthogonal signals can be selected at each receiving channel,and range compression is completed at the same time.Based on PCA theory,using the minimum entropy criterion to rearrange the echo data after target’s velocity is estimated,the azimuth imaging and MTRC correction will be finished finally.The analysis of theory and the results of simulating show that minimum CIT of MIMO-ISAR imaging method is 1 MN of conventional ISAR imaging method with the same azimuth resolution.It means that most of flying targets can satisfy the condition that targets should move smoothly during CIT,therefore,the applicability and the quality of ISAR imaging will be improved.关键词：MIMO(multiple-input multiple-output);ISAR(inverse synthetic aperture radar);PCA(phase center approximation);imaging0|2|15更新时间：2025-07-02
- 摘要：When passive tracking a jammer by a phased array active radar,the scattering power from scatters of the jammer enters the receiver through sidelobes,which is the main noise power to influence tracking precision.The formulas to calculate the jamming power from the jammer received by mainlobe and the scattering power from scatters of the jammer through sidelobes are derived.The characteristic of the jamming power received by searching beams outside certain space around the jammer is analyzed in detail and a new method of estimating jam-noise ratio is presented:the jamming power received by searching beams is substituted for the scattering power hard to get actually.Analysis and experiments show the substitution and estimation are reasonable and feasible.关键词：anti-jamming technology;passive tracking;jam-noise ratio;phased array radar0|2|1更新时间：2025-07-02
- 摘要：The azimuth resolution of conventional spaceborne SAR systems is in conflict with swath width because of the minimum antenna area constraint.The conflict can be solved by using distributed small satellite SAR systems,thus achieving a wide swath and high resolution SAR image of the observed scene.Furthermore,if the flying formation of the distributed small satellites has large cross-track baselines(called InSAR formation),we can also achieve the terrain height information of the scene simultaneously.However,many challenges arise in constellation InSAR system.In particular,envelope registration and sample selection for adaptive processing are the two main challenges.This paper investigates data processing approaches to retrieve the three-dimensional terrain for the distributed small satellite InSAR systems.The effectiveness of the proposed approach is verified by simulated data.关键词：distributed small satellites;Doppler ambiguity;digital elevation model(DEM);array signal processing0|2|5更新时间：2025-07-02
- 摘要：A new identification procedure for the nonlinear systems which can be described by Wiener-Hammerstein models is proposed by using correlation,multidimentional z transform,deconvolution and a simple least squares algorithm.Two linear subsystems and nonlinear systems in models can be identified and estimated separately with this procedure.Calculation is simple,and data are fewer.Simulation results illustrate the validity of the proposed algorithm.关键词：Wiener-Hammerstein models;nonlinear systems;identification0|2|3更新时间：2025-07-02
- 摘要：The parametric estimation of the fully polarized scattering center is studied.The key problem is solved by the Constrained Total Least Squares (CTLS) method based on the Damped Exponentials (DE) model of the fully polarized scattering centers,and then the estimations of the distances and types can be obtained.Then via solving the measurement-equation,the complex amplitudes of the scattering matrix are derived using Total Least Squares (TLS) method.The precisions are considered through calculating the means and variances of the estimated parameters.And more,the estimated theory is developed to adapt to another situation of different noise covariance in different channels.At last simulations are performed and our estimation theory is proved to be effective.关键词：CTLS;Fully polarized scattering center;DE0|2|1更新时间：2025-07-02
- 摘要：The pattern of every element in conformal array has a different direction because of the curvature of conformal carrier,which results in polarization diversity of conformal array antenna.In order to describe the polarization diversity of conformal array antenna,polarization parameters of incident signals are contained in observations.Consequently it is usually required that the polarization parameters and DOA(Direction-Of-Arrival) of incident sources are jointly estimated.A blind DOA estimation method with respect to polarization diversity is proposed on the basis of ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) algorithm for conical conformal array antenna,in which three pairs of special subarrays are designed.Azimuth and elevation angles of incident sources are found without knowing the polarization parameters by decoupling them.Then the CRB (Cramer-Rao Bound) of this method is derived and the validity of this algorithm is confirmed by Monte Carlo computer simulations.关键词：conical conformal array antenna;direction-of-arrival estimation;ESPRIT;performance analysis;Cramer-Rao bound0|2|25更新时间：2025-07-02
- 摘要：The traditional unitary space-time modulation system is generally based on the assumption of independent and identically distributed channel coefficients.However,this condition is hard to satisfy in practice,the spatial correlation among antennas deteriorates the performance.This paper proposed a maximum-likelihood multiple-symbol differential-detection algorithm for unitary space-time system with spatial correlation.By using the first symbol of every observation window as pilot symbols,the transmit efficiency approximates to 1.Moreover,the proposed algorithm does not require the feedback channel.The fast search for the maximum-likelihood solution can be done by sphere decoding aligorthm.Simulation results show that our scheme can improve the bit error rate performance effectively in spatial correlated channels with a small cost.关键词：spatial correlation;unitary space-time modulation;multiple symbol differential detection (MSDD)0|2|1更新时间：2025-07-02
- 摘要：Based on the analysis of relationship between the geometry dilution of precision(GDOP)and satellite elevation as well as azimuth,a new fast satellite selection algorithm applicable to GNSS receiver was presentedr. In this algorithm,firstly the exponent attenuation model of relationship is built between pre-and-post GDOP and optimal satellites number,through which the number of selecting satellites was decided according to the precision of user’s requirement.Then all visible satellites are classified by elevation into three sections:low elevation,medium elevation and high elevation.Finally parts of satellites in medium elevation section are excluded through sorting,differentiating to fulfill satellite selection.The computer simulations demonstrate that this method introduces much lower complexity compared to conventional algorithms,and decreases by about 50% the navigation computation with only 12% positioning accuracy descending.关键词：global navigation satellite system(GNSS);integrated navigation;fast satellite selection algorithm;geometry dilution of precision(GDOP)1|3|16更新时间：2025-07-02
- 摘要：For ISAR echoes of air micro-motion targets with high-speed rotating parts,this paper presents a low chirp rate matching based algorithm to separate the echoes of rigid body from that of the rotating parts.Meanwhile,an inverse Radon transform based algorithm is proposed to estimate the image of rotating scatters,according to the characteristics of micro-Doppler signals.Therefore,well-focused ISAR imaging for both the rotating parts and the rigid body can be obtained.Finally,the results of simulated and measured data have proved the validity of the proposed algorithm.关键词：inverse synthetic aperture radar(ISAR);micro-motion target imaging;low chirp rate matched filtering;inverse Radon transform0|2|25更新时间：2025-07-02
- 摘要：Aiming at dealing with multiple active decoys deception jamming in the background of ballistic missile penetration,a new ballistic missile tracking algorithm with the capability of anti-jamming is proposed.By utilizing the advantage of measurement linearity in spherical coordinates,the algorithm can not only improve the tracking accuracy of true target,but also can estimate the delay range of active decoys in real time.The filtering result can be viewed as an auxiliary parameter to discriminate these active decoys.Firstly,the delay range is served as a state variable augmented to the spherical coordinate state vector.The theoretical motion model for ballistic targets is derived in a general way.Secondly,a spherical-coordinate based extended Kalman filter(EKF)is adopted to estimate the delay range and the smaller ones can be viewed as being from physical targets while the larger ones can be viewed as active decoys.Finally,performance analysis under the influence of related factors is also covered.The advantage of the algorithm lies in its real-time feature and integration of tracking and discrimination.关键词：ballistic missile tracking;active decoys;spherical coordinates;extended Kalman filter(EKF);discrimination0|2|10更新时间：2025-07-02
- 摘要：By performing eigen-decomposition(ED)to covariance matrix of intermediate frequency(IF) communication signals,eigenvalues’distribution in signal subspace and noise subspace is obtained.According to the distribution difference,a fast blind detection algorithm based on eigenvalue analysis is presented.Relationships between detection quantity and signal-to-noise ratio(SNR) are deduced,and detection performances are analyzed theoretically.Computational complexity is also analyzed.For commonly used communication signals,such as MPSK, MQAM,MFSK,etc,simulation results indicate:when false alarm probability is set to less than 1%,bind detection probability reaches above 90% at SNR -10dB.关键词：information processing technology;blind detection;eigenvalue analysis;communication signals0|2|2更新时间：2025-07-02
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Research on the Attacking Mode for Blind Launch of Anti-Ship Missiles with Route-Planning Capability
摘要：The emergence of the new intelligent long range anti-ship missile(ASM)boosts the development of the relevant launching modes.The key idea of the blind launch of the ASM is that when the target position is not accurately known,based on the maneuvering ability and the long-range large-sector searching ability of the ASM,it can be launched to cover the potential distribution area of the target so as to perform its active combat capability.The optimal attacking mode for blind launch of ASM is modeled and simulated.The key elements that influence the optimal attacking mode are analyzed based on the simulation results which show that when the number of the launched ASMs is small or the counterattacking fire of the target is strong,all the ASMs should be launched towards the center of the target distribution area;when the potential distribution area of the target is large,the ASMs should be averagely assigned to the multiple aiming points.关键词：anti-ship missile;aiming point;launch mode;blind launch0|2|3更新时间：2025-07-02 - 摘要：A broad-band spatial power-combining system and its simplification model based on main mode characteristic in radial waveguide was presented.The results show the passive combining system has a minimum combining efficiency of 88 percent from 9GHz to 14GHz,and the active one with 16 MMICs has an average combining efficiency of 83% and produces up to 159-W output power within the band of interest(11.9GHz~12.3GHz).关键词：microwave;solid-state power amplifier;spatial power combining;radial waveguide0|2|2更新时间：2025-07-02
- 摘要：The DOAs and Dopplers of the echoed signal from targets are very important parameters in some applications for radar and sonar.This paper proposes a new cost function which is based on the likelihood function amplified with a nonlinear function,and the global convergence of this function can be obtained more easily than the original cost function.An Importance Sampling (IS) technique based on Monte Carlo method is proposed to find the optimum of this cost function,and the suitable importance function is chosen to estimate these parameters.All parameters are paired automatically and this technique can be applied on the arbitrary known array shape.Computer simulations show that the proposed method is superior to other methods based on subspace decomposition under the condition of low SNR and small snapshots,and the MSEs of Dopplers and DOAs in this method are very close to CRLB.关键词：joint estimation of dopplers and DOAs;monte carlo method;importance sampling;maximum likelihood estimation (MLE)0|2|4更新时间：2025-07-02
- 摘要：An approach is proposed to automatically detect EEG spikes,based on sparse representation of signals.Firstly,Gaussian function and its first and second derivations are used as the generating functions to construct the redundant multi-component dictionary.Secondly,the M-term sparse approximation is obtained using matching pursuit method in our dictionary.Various morphological structure features of transients can be extracted accurately,utilizing the derivative information of the sparse approximation and the structure parameters of atoms.Finally,a detection algorithm is presented,based on morphological structure match.It can overcome the Gabor dictionary's shortcomings that can’t detect the series of spike-wave complexes,moreover,can reject background transients and artifacts effectively.The experimental results indicate that our detection technique yields high sensitivity of 93.9 percent and selectivity of 88.0 percent evaluated on clinical EEGs.关键词：spike detection;sparse representation;multi-component dictionary;matching pursuit;morphological structure2|2|6更新时间：2025-07-02
- 摘要：In complicated acoustic environment where the characteristics of noise field and reverberation time are unknown,the performance of the speech enhancement methods with microphone array face a great challenge.A speech enhancement method based on phrase-errors of the noisy speech signals and post-filter is proposed.First,in each frame of the microphone array signals,by using the phrase-errors of the adjacent noisy speech signals,we can construct scaling coefficients to preprocess the noisy speeches,and then the preprocessed signals are obtained.Second,by using the fixed beamformer,independent component analysis and post-filter,we can suppress the noises further.Simulation results show the effectiveness of the proposed method in various noise fields with some reverberation.关键词：microphone array;phrase-error;independent component analysis;post-filter0|2|2更新时间：2025-07-02
- 摘要：In the actual system for multi-channel airborne radar,the DPCA requirement is difficult to be satisfied and thus the performance of clutter suppression is degraded,because the amplitude/phase errors of the system and the nonsteady movement of the aircraft cannot be avoided.The prefilter technique is proposed to compensate the movement errors of the aircraft,and it guarantees that the loss of the signal of moving targets be as little as possible.Subsequently,the traditional adaptive DPCA technique can be used to compensate the amplitude and phase errors of the system.Unfortunately,when there exist strong moving targets in the samples,the adaptive weight evaluated deviates from the optimum weight greatly,and thus the performance of clutter suppression is degraded.To deal with this problem,a robust dual-channel adaptive DPCA method for clutter suppression is proposed based on the criterion of maximum signal-to-noise ratio.Then we analyze the influence of the prefilter on the moving targets,and provide the cancellation curve of the moving targets after the prefilter processing.Finally,the effectiveness of the method proposed is validated by the experiments of measured data and simulated targets.关键词：multi-channel airborne radar;error compensation;DPCA;clutter suppression;curve of target response0|2|5更新时间：2025-07-02
- 摘要：Used as basic data level,the microstructure of a state variable is described from the temporal mode,period mode of continuous deformation,mutation intensity and self-occlusion features,and the models are resulted from cognitive psychology analysis in the process of human-computer interaction.At the same time,the approach to dynamically assign the particles number over frames for reduction of the average particles number is probed into as well.The algorithm presented is implemented with VC+ +,and the experimental results are summarized and compared with other previous researches.By examining several real videos of moving hands,we find that our algorithm can decrease the sampled particle number more effectively than the classical particle filtering.关键词：human hand tracking;particle filtering;microstructure of state variable;sampled number reduction;cognitive psychology0|2|5更新时间：2025-07-02
- 摘要：The adaptive monopulse at subarray level is required for applying monopulse technique in multi-function phased array radar.The two-stage processing approach is studied,which is for adaptive monopulse at subarray level in planar phased array.The four-channel monopulse system is adopted,in which the delta-delta channel is used as an auxiliary channel.The signal model of adaptive monopulse at subarray level is presented.An improved two-stage adaptive jamming suppression approach at subarray level is proposed.The first stage of adaptive processing is used to suppress the sidelobe jamming,while maintaining the mainlobe shape at the same time.Besides,we modify conventional approach which combines ADBF at subarray level with mainlobe maintenance technique,so that it suppresses sidelobe of adaptive patterns effectively and improves mainlobe maintenance effect remarkably.The second stage of adaptive processing is used to suppress mainlobe jamming,while preserving an undistorted monopulse ratio.Simulation results demonstrate that the presented approach can suppress jamming effectively,while preserving good monopulse performance and approximating the adaptive monopulse ratio to the quiescent one at the same time.关键词：adaptive monopulse;phased array at subarray level;jamming suppression;mainlobe jamming;adaptive baemforming0|2|14更新时间：2025-07-02
- 摘要：XCP has a weakness in a multi-bottleneck network,a bottleneck link may have a significantly decline in utilization,and some flows may not receive their fair rates.According to the control theory,we propose an XCP bandwidth compensation algorithm based on PII controller.Extensive simulations show that this algorithm overcomes the weakness of XCP,every link can achieve 100% link utilization,and every flow can get its max-min fair allocation.关键词：XCP;multi-bottleneck networks;PII controller;congestion control0|2|1更新时间：2025-07-02
- 摘要：An important problem in evolutionary multi-objective optimization is how to build non-dominated set efficiently.An algorithm is proposed for building non-dominated set.In the algorithm,the individuals are sorted based on normalized parameter,and all individuals can be ranked linearly in evolutionary colony.The correlation theory and proof are presented at the same time.On the basis of the proposed algorithm,every individual in evolutionary colony is only compared with those individuals that have been in the non-dominated set,and this comparison is single-direction.Thus the quantity of comparison among the individuals is cut down,and non-dominated set can be built efficiently.This is validated by theoretical analysis and several experiments.The results show that the approach is better than other approaches and exhibits good properties.关键词：multi-objective evolutionary algorithm;non-dominated set;normalized sort0|2|8更新时间：2025-07-02
- 摘要：Target detection for hyperspectral imagery has important academic value and prospective applications both in civil and military areas.And it has been a hot spot in the areas of target recognition and remote sensing information processing.Based on the characteristics and development of hyperspectral imaging,this paper surveys the potential typical applications of target detection for hyperspectral imagery,along with the relevant experiments and systems at home and abroad.Then,the development of current theory and algorithm are summarized.Challenges of target detection for hyperspectral imagery and the direction of future progress are also discussed.关键词：hyperspectral imagery;Target Detection;algorithms;typical application2|2|22更新时间：2025-07-02
- 摘要：A dwell scheduling algorithm for DAR is proposed according to the characteristics of signal processing in DAR.The dwell scheduling algorithm is based on an online pulse interleaving technique,which realizes the interleaving execution of different dwell tasks under the time and energy constraints.The waiting durations can be used to transmit beams or receive returning data of other dwells.Furthermore,the waiting durations of different dwells can be overlapped.Simulation results demonstrate that compared with conventional dwell scheduling algorithm,the proposed one can achieve smaller task drop ratio and thus higher hit value ratio for the effective utilization of the waiting and receiving durations.关键词：digital array radar;dwell scheduling;pulse interleaving;time constraint;energy constraint1|2|16更新时间：2025-07-02
- 摘要：The rank quantization(RQ)nonparametric detector plays an important role for target detection in actual radar system.By means of analytic methods,the detection performance of the rank quantization detector is investigated in homogeneous background and nonhomogeneous background caused by multiple targets,against the Weibull distributed background,for a Swerling II targets model.The analytic expressions of detection and false alarm probabilities for the RQ nonparametric detector in Weibull backgrounds are derived, and a comparison to the detection performance of classic parametric detector cell-averaging(CA)scheme is made.关键词：radar;nonparametric;rank quantization;CFAR;Target Detection0|2|4更新时间：2025-07-02
- 摘要：A Bootstrap—adaptive chaos clone network is put forward for drift forecasting modeling of gyro.Drift times series of gyro has little samples,in order to obtain statistic optimization estimate of the forecasting model, training strategy of adaptive chaos clone network is designed based on Bootstrap method.String techniques are used to produce compound function antibodies,ability of the forecasting model which approach strong nonlinear function in complex function subspace is high.A series evolve operator in adaptive chaos clone network is structured,adaptability of antibodies improve in evolution with chaos character.Forecasting modeling experiments show that forecasting model built by Bootstrap—adaptive chaos clone network is of smooth training and test precision,compared with several typical forecasting algorithm,the modeling approach is flexible,forecasting model has well adaptability and can meet the requirements of engineering application.关键词：Bootstrap;adaptive chaos clonal network;drift forecasting of gyro;compound function antibodies0|2|1更新时间：2025-07-02
- 摘要：A DOA(Direction of Arrival) estimator based on MIMO sonar system is proposed to estimate the DOA of targets.Firstly,orthogonal signals are sent out by transmitting sensors and the output of receiving sensors is processed by a matched filter using transmitting signals.Then,the solution of space fitting is achieved by least square method.Finally,perfect sampling,a kind of Markov Monte Carlo methods,is combined with least square method(PLS) to lighten the computation.Simulations show that in the case of two sources,the PLS provides similar performance to that achieved by the ML method and better performance than MVM method in low and mid SNR range,but its computational cost is much reduced comparing with that of ML.关键词：MIMO(Multiple Input Multiple Output);least square;DOA(Direction of Arrival)estimation;perfect sampling;computational complexity0|2|4更新时间：2025-07-02
- 摘要：The fractional Fourier transform(FRFT)is of better time frequency analysis character than the traditional Fourier transform.The filtering in the optimal fractional Fourier domain(FRFD)can estimate some special cases of non-stationary signals and systems with minimum mean square error.The theorem for the multirate filter bank in the FRFD leads to the efficient structure of filtering in the FRFD and the multi-resolution analysis of signal in the FRFD.But the existing perfect reconstruction filter banks in the FRFD are of special form,which cannot satisfy some practices.This paper proposes the generalized design method for the perfect reconstruction filter banks in the FRFD based on the FRFD analysis of sampling rate conversion and the fractional convolution theorem,which are the basis of the applications of filter bank theory in the FRFD.At last,the simulations verify the generalized design method.关键词：fractional Fourier transform;M-channel filter banks;signal polyphase representation;perfect reconstruction;fractional convolution0|2|4更新时间：2025-07-02
- 摘要：A three-dimensional fully electromagnetic particle parallel program is developed to simulate non-linear temporal evolution of the interaction of intense relativistic electron beams with electromagnetic in the high power microwave devices with complicated geometry.This paper presents the two level parallel domain decomposition strategy used in the parallel program,namely,block and patch strategy,and the parallel time integration algorithm based on it.A typical device with complex geometry is simulated by the parallel program on thousands of processors,which shows the good scalability and the results are comparable to several famous softwares for the same purpose.关键词：parallel computing;parallel domain decomposition;high power microwave;particle-in-cell0|2|0更新时间：2025-07-02
- 摘要：The novel resonant DC link voltage source inverter combined merits of pulse width modulation (PWM) and soft switching.However,auxiliary resonant DC link has a four-element LCCC structure,and it lead to inverter has complex transient dynamics,high dimension and time variation.It is difficult to obtain soft switching condition and design rule of inverter by means of differential equation.The state-plane analysis technique is established for the novel resonant DC link inverter in this paper.Making use of three state planes to express four dimensions circuit,transient dynamics,soft switching condition and design rule are presented.Subsequent experiment is performed for Brushless DC Motor (BLDCM),and their results confirm validity of analysis and design rule presented.关键词：state plane analysis;soft switching condition;design rule;inverter;transient dynamics0|2|2更新时间：2025-07-02
- 摘要：A high accurate frequency estimation algorithm of coherent pulse train (CPT) was presented.The output signal-to-noise ratio (SNR) was enhanced through intrapulse correlation accumulation.The requirement for coherent frequency estimation was analyzed and the close-form of the input SNR threshold was derived.Subsequently,we investigated the relationship of the SNR threshold,the total number of samples and the duty cycle.Simulation results show that the performance of the proposed algorithm approaches the Cramer-Rao lower bound of the coherent sinusoidal pulse train when the SNR is higher than the SNR threshold.关键词：coherent pulse train;frequency estimation;signal-to-noise ratio threshold0|2|6更新时间：2025-07-02
- 摘要：The shortcomings of the empirical mode decomposition(EMD)were studied when it was used to process signals,and several incorrect conclusions on EMD and HHT(Hilbert-Huang Transform)were analyzed.The rationality of choosing the inflections of a signal as a measurement for the oscillation mode imbedded in the signal itself was verified,and enhanced inflection-based algorithm was provided to improve the behavior of EMD.The results of processing synthetic and practical signals show its right and efficiency.Based on the new algorithm,the definition of intrinsic mode function(IMF)was studied and modified.关键词：instantaneous frequency;inflections;EMD0|2|0更新时间：2025-07-02
- 摘要：A method for estimating two dimensional parameters of near field sources based on third-order cyclic moment was proposed.Based on uniform linear array and third-order cyclic moment,the algorithm constructed the three matrixes of third-order cyclic moment.Then it estimated the bearing and range parameters of near-field sources.The algorithm removed additive noise and multiplicated noise by cyclic statistics and pre-calibration respectively,so it can work well in multiplicated noise environment or multiplicated noise and additive noise environment.Simulation results show the algorithm’s effectiveness.关键词：near-field source localization;multiplicated noise;bearing estimate;range estimate0|2|1更新时间：2025-07-02
- 摘要：A sine-wave fitting method is put forward.Unlike classical three-or four-parameter sine-wave fitting procedure,this method avoids selecting initial value of the parameters and working out the nonlinear equations.By means of both the Hilbert-Huang transform(HHT) and the traversal method,under the circumstances of 7-bit signal source,and with both the harmonic distortion and the noise distortion existing,parameters of fitting sinusoid are obtained from the analog-to-digital converter(ADC) output data,and then the effective number of bits(ENOBs) of 14-bit ADC are tested accurately.The simulation proves that this algorithm is precise and efficient.关键词：high-resolution;analog-to-digital converter;effective number of bits;Hilbert-Huang transform;traversal method0|2|4更新时间：2025-07-02
- 摘要：In order to really apply the shaft-rate EM field to new type mine fuze,the EM fields at a fixed field point produced by a moving horizontally-directed time-harmonic dipole located in the three-layer medium have been derived.The whole process is divided into two steps,in the first step,the EM fields at a fixed field point produced by a fixed dipole are derived,then based on the basic principle of the special theory of relativity and Lorentz transformation,the EM field produced by the moving dipole are derived.Taking a ELF dipole moving slowly in the shallow ocean for example,the numerical calculations of its EM fields are carried out,some valuable conclusions are reached through contrasting the calculation results of different conditions.In the end,the practicalities and validities of the calculation results are proved through contrasting the calculation results with experimentation data.关键词：horizontally-directed time-harmonic dipole;Maxwell equation;Lorentz transformation;EM field0|2|6更新时间：2025-07-02
- 摘要：A new method for the detection of weak light signal using pseudo-random sequences(PNs) was introduced.A beam of light modulated by PNs was injected into the measurement system;the output light signal was detected by a photoelectric diode then dealt with the correlate detection technology using PNs.Because the characteristic of PNs is similar to that of the white noise,the disturbance and noise in the process of measurement had been a little influence on the peak value of the correlation function,so the weak light signal could be detected clearly.The results from the simulation and experiment proved that this method was an effective way for detection of weak light signals.The prime signal can be detected when the signal noise ratio(SNR) is as low as -15dB;the gain of SNR is about 30dB.关键词：pseudo-random sequence;weak light signal;correlation detection0|2|1更新时间：2025-07-02
- 摘要：The azimuth quadratic phase term caused by the complex movement of target in the air or on the sea deteriorates the azimuth focusing quality.RD imaging algorithm,WVD imaging algorithm,Radon-Wigner imaging algorithm and DechirpClean imaging algorithm,due to bad imaging effect and inefficient operation and so on,are unfit for ISAR imaging of the complex motion target.Since,this paper shows a new method of ISAR imaging based on the scale transform in time-frequency distribution plane that changes each range cell data after range alignment correction to the new data in the time-frequency plane and solves the coupling effect between the signal time and the correlation function delay by the scale change.In doing that,the bias caused by the azimuth quadratic phase term becomes the beeline parallel to the time axis,at the same time,the ISAR image of the complex motion target can be acquired by the energy accumulation along the rectified beeline in the time-frequency plane.This method has many advantages,including the nice imaging effect and the high efficient operation and so on.The simulated and real data result confirm the effectiveness of this method at the end of this paper.关键词：inverse synthetic aperture radar(ISAR);the time-frequency distribution;the scale transform;the quadratic phase term;efficient operation0|2|4更新时间：2025-07-02
- 摘要：The rapid growth of demand for wireless transmission has placed great pressure on the background noise extraction and detection. This paper puts forward a new method to extract background noise based on the texture feature. To separate the signals from background noise,it utilizes the method of smoothing filtering and threshold limit to achieve the background noise texture feature. Experiments and statistical analyses about background noise extraction were conducted with using the method of smoothing filtering and threshold limit. The measurement results and analyses prove that this method is robust and can extract various kinds of background noise in a wide spectrum range,and also it can overcome the influence of the distribution of background noise and signal bandwidth.关键词：background noise;feature extraction;texture;smoothing filtering0|2|6更新时间：2025-07-02
- 摘要：Effects of element failure in different cases are discussed on array pattern,clutter characteristic and space-time adaptive processing (STAP) performance in allusion to a rectangle array.When the array is weighted,the nearer the failing element is from the array center,the more the main lobe of array pattern descends and the side lobes ascend.Clutter rank increases as the number of the failing elements in sub-array increases,whereas when the sub-array fails,the clutter rank decreases to almost that of no element failure.In the end effects of element failure on signal coherent integration are analyzed,and two STAP algorithms are employed in computer simulation to illuminate the effects of element failure on STAP.Element failure can lead to space adaptive pattern aberrance besides increasing clutter rank,which affects the performance of algorithms with low degree of freedom (DOF) more.To solve the problem,an improved method of deeply-weighting is presented,and an improved performance is obtained.关键词：element failure;sub-array failure;space-time adaptive processing (STAP);array pattern0|2|2更新时间：2025-07-02
- 摘要：The accurate estimation of the center frequency and the chirp rate of linear frequency modulated signal play an important role in radar signal processing.The WVD transform can show the characteristic of the center frequency and the chirp rate of linear frequency modulation signal,but the cross-term of signals deteriorates the precision of the estimation of the center frequency and the chirp rate.In order to estimate those parameters of signal better,this paper proposes a new method of the parameters estimation of linear frequency modulated signal based on STTFD (the scale transform in time-frequency distribution plane),by which the frequency of signal in time-frequency distribution plane by the scale-transform to remove the coupling effect between the signal time and the correlation function delay changes from the linear distribution along the time axis to the constant distribution along the time axis,then the center frequency and the chirp rate of linear frequency modulated signal can be estimated by the peak value position of signal acquired by doing FFT along the time axis in time-frequency distribution plane.At the same time,the analysis of the characteristic of STTFD and the effect of the scale-transform constant and the correlation function delay on STTFD is given.Finally,the simulation data confirms the characteristic of STTFD and the effectiveness of the parameters estimation of linear frequency modulated signal based on STTFD.关键词：STTFD (the scale transform in time-frequency distribution plane);time-frequency plane;scale transform;center frequency;chirp rate0|2|2更新时间：2025-07-02
- 摘要：Aiming at the color features of human skin and mucosa,a color constancy model is established to collect and analyze medical true color images under natural light condition.In LAB color space,a TRM (topology resolve-map) model is established to restore these colors from the gathered images to standard values by linear mapping to the one-dimensional L* space and triangulation mapping to the two-dimensional a*b* space.Via regulating and restoring the 13 skin colors in SG color codes,the experimental results show that the TRM model has good accuracy and stability and the differences of delta L,delta ab and delta E are dramatically decreased.0|2|13更新时间：2025-07-02
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