This paper deals with the method of using quasi observation. In the paper a simple algorithm is developed for the adjustment computation with quasi observation at first. And then the ability of quasi observation to im...This paper deals with the method of using quasi observation. In the paper a simple algorithm is developed for the adjustment computation with quasi observation at first. And then the ability of quasi observation to improve ambiguity search technique is studied in detail. The robustness of the method is also discussed. A method to determine the weight of quasi observation is proposed. The results show that a prior height can be taken as a quasi observation and used together with GPS observations. It can strengthen residual tests, especially in situation where there are fewer satellites in the sky. It also can change structure of incorrect solutions, which will theoretically make less incorrect solutions left in search space. At last the field tests are carried out to show that the proposed method is effective. The success rate of ambiguity resolution in the four field tests is improved significantly.展开更多
For radar high resolution range profile (HRRP) recognition, three aspects are of great importance to improve the performance, i.e. discrimination for outlier, classification for inner and an accurate description for f...For radar high resolution range profile (HRRP) recognition, three aspects are of great importance to improve the performance, i.e. discrimination for outlier, classification for inner and an accurate description for feature space. To tackle these issues, a novel target recognition method is designed, denoted by the multiple support vectors (multi-SV) method. With the proposed method, a special framework is constructed by a treble correlate support vector model to segment the feature space to two regions with the distribution of density, and then the description and classification hyperplane for each region are achieved. Based on the support vector framework, this method needs less memory and computation complexity to fit practical radar HRRP recognition. Finally, the experiment based on the measured data verifies the excellent performance of this method.展开更多
It is an attractive method to combine GPS observations with the information from other surveying system to improve the ambiguity resolution. This research is conducted to investigate how to obtain the prior height inf...It is an attractive method to combine GPS observations with the information from other surveying system to improve the ambiguity resolution. This research is conducted to investigate how to obtain the prior height information in bathymetric surveying by GPS positioning and how to use the prior height information and to obtain a robust result. The authors deal with the collection and the description of the prior height and the method using height validation to improve the ambiguity resolution. The principle of the method, the relationships between the height threshold and the ambiguity search space are presented. A method to determine the threshold for the height validation is suggested. The field tests are carried out to show the feasibility of the proposed methods.展开更多
Orthogonal frequency division multiplexing（OFDM） radar with multicarrier phase-coded waveforms has been recently introduced to achieve high range resolution.The conventional method for obtaining the high resolution ...Orthogonal frequency division multiplexing（OFDM） radar with multicarrier phase-coded waveforms has been recently introduced to achieve high range resolution.The conventional method for obtaining the high resolution range profile（HRRP） is based on matched filters.A method of synthesizing HRRP based on the fast Fourier transform（FFT） and decoding is proposed.The mathematical expressions of HRRP are derived by assuming an elementary scenario of point-scattering targets.Based on the characteristic of OFDM multicarrier signals,it mainly analyzes the influence on HRRP exerted by several factors,such as velocity compensation errors,the sampling frequency offset,and so on.The conclusions are significant for the design of the OFDM imaging radar.Finally,the simulation results demonstrate the validity of the conclusions.展开更多
In a previous companion paper [1], the potential advantages of high resolution radar for improved target detection were introduced. In particular, the concept of shaping both the transmitted waveform and the receiving...In a previous companion paper [1], the potential advantages of high resolution radar for improved target detection were introduced. In particular, the concept of shaping both the transmitted waveform and the receiving processor in accordance to the expected target down-range profile was highlighted and performance predictions were provided. In this paper, we present and evaluate an adaptive scheme devised to on-line estimate the target profile, in order to overcome a limited a-priori knowledge. In addition, we introduce a more general model of target impulse response, based on a statistical description, and we discuss the corresponding processing scheme and detection performance.展开更多
The contents ofMg, Al, Si, Ti, Cr, Mn, Fe, Co, Cu, Ga, As, Se, Cd, Sb, Pb and Bi in high purity nickel were determined by high resolution inductively coupled plasma mass spectrometry （HR-ICP-MS）. The sample was diss...The contents ofMg, Al, Si, Ti, Cr, Mn, Fe, Co, Cu, Ga, As, Se, Cd, Sb, Pb and Bi in high purity nickel were determined by high resolution inductively coupled plasma mass spectrometry （HR-ICP-MS）. The sample was dissolved in HNO3 and HCI by microwave digestion. Most of the spectral interferences could be avoided by measuring in the high resolution mode. The matrix effects because of the presence of excess HC1 and nickel were evaluated. Correction for matrix effects was made using Sc, Rh and T1 as internal standards. The optimum conditions for the determination were tested and discussed. The detection limits range from 0.012 to 1.76 ~tg/g depending on the type of elements. The applicability of the proposed method is also validated by the analysis of high purity nickel reference material （NIST SRM 671）. The relative standard deviation （RSD） is less than 3.3%. Results for determination of trace elements in high purity nickel were presented.展开更多
In a global positioning system(GPS)passive radar,a high resolution requires a high sampling frequency,which increases the computational load.Balancing the computational load and the range resolution is challenging.Thi...In a global positioning system(GPS)passive radar,a high resolution requires a high sampling frequency,which increases the computational load.Balancing the computational load and the range resolution is challenging.This paper presents a method to trade off the range resolution and the computational load by experimentally determining the optimal sampling frequency through an analysis of multiple sets of GPS satellite data at different sampling frequencies.The test data are used to construct a range resolution-sampling frequency trade-off model using least-squares estimation.The theoretical analysis shows that the experimental data are the best fit using smoothing and nthorder derivative splines.Using field GPS C/A code signal-based GPS radar,the trade-off between the optimal sampling frequency is determined to be in the 20461.25–24553.5 kHz range,which supports a resolution of 43–48 m.Compared with the conventional method,the CPU time is reduced by approximately 50%.展开更多
For a synthetic aperture radar（SAR） system mounted on a geostationary Earth orbit（GEO） satellite, the track can be curvilinear. Thus, a bistatic SAR system based up on geostationary transmitter and ＂receive-only...For a synthetic aperture radar（SAR） system mounted on a geostationary Earth orbit（GEO） satellite, the track can be curvilinear. Thus, a bistatic SAR system based up on geostationary transmitter and ＂receive-only＂ SAR system onboard airplanes, namely GEO spaceborne-airborne bistatic（GEO SA-Bi SAR）, is significantly different from the traditional bistatic SAR. This paper mainly studies the resolution characteristic of the sliding spotlight GEO SA-Bi SAR system. Firstly, the common azimuth coverage and coherent accumulated time are theoretically analyzed in detail. Then,based on the gradient method, the accurate two dimensional resolution of a GEO SA-Bi SAR system is analytically calculated. Finally, the simulation data show the correctness and effectiveness of the proposed resolution analysis method.展开更多
Mixture model based image segmentation method, which assumes that image pixels are independent and do not consider the position relationship between pixels, is not robust to noise and usually leads to misclassificatio...Mixture model based image segmentation method, which assumes that image pixels are independent and do not consider the position relationship between pixels, is not robust to noise and usually leads to misclassification. A new segmentation method, called multi-resolution Ganssian mixture model method, is proposed. First, an image pyramid is constructed and son-father link relationship is built between each level of pyramid. Then the mixture model segmentation method is applied to the top level. The segmentation result on the top level is passed top-down to the bottom level according to the son-father link relationship between levels. The proposed method considers not only local but also global information of image, it overcomes the effect of noise and can obtain better segmentation result. Experimental result demonstrates its effectiveness.展开更多
Sparse representation has attracted extensive attention and performed well on image super-resolution（SR） in the last decade. However, many current image SR methods face the contradiction of detail recovery and artif...Sparse representation has attracted extensive attention and performed well on image super-resolution（SR） in the last decade. However, many current image SR methods face the contradiction of detail recovery and artifact suppression. We propose a multi-resolution dictionary learning（MRDL） model to solve this contradiction, and give a fast single image SR method based on the MRDL model. To obtain the MRDL model, we first extract multi-scale patches by using our proposed adaptive patch partition method（APPM）. The APPM divides images into patches of different sizes according to their detail richness. Then, the multiresolution dictionary pairs, which contain structural primitives of various resolutions, can be trained from these multi-scale patches.Owing to the MRDL strategy, our SR algorithm not only recovers details well, with less jag and noise, but also significantly improves the computational efficiency. Experimental results validate that our algorithm performs better than other SR methods in evaluation metrics and visual perception.展开更多
Based on the squint mode, a high resolution wide swath revisit synthetic aperture radar （SAR） imaging mode is pro- posed. The transmitting antennas are configured as the single phase center multiple azimuth beams （...Based on the squint mode, a high resolution wide swath revisit synthetic aperture radar （SAR） imaging mode is pro- posed. The transmitting antennas are configured as the single phase center multiple azimuth beams （SPC MAB）. The formed two beams point to two different directions to obtain two images of the observed scenario. The receiving antennas are configured as displaced phase center multiple azimuth beams （DPC MAB） to decrease the required pulse repetition frequency （PRF）. The de- creased PRF can ensure the high resolution wide swath imaging. Based on the analysis of the character of the return signal, a pro- cessing method named multiple beam multiple channel algorithm （MBMCA） is proposed to separate the aliased sub-beams＇ echoes. The separated echoes are focused respectively to get the revisit imaging to the observed scenario. The simulation experiments ve- rify the validity and correctness of the proposed imaging mode and processing algorithm.展开更多
The azimuth resolution improvement problem is solved via a coherent combination of synthetic aperture radar （SAR） ima-ges with the quasi-non-overlapped Doppler bandwidth. Prior to the spectra combination, SAR images...The azimuth resolution improvement problem is solved via a coherent combination of synthetic aperture radar （SAR） ima-ges with the quasi-non-overlapped Doppler bandwidth. Prior to the spectra combination, SAR images should be coregistered, while phase biases induced by topography, atmospheric propagation delays and baseline measurement errors should be calibrated. However, the coregistration accuracy suffers from large Doppler decorrelation caused by the quasi-non-overlapped Doppler band-width. Furthermore, the method used to estimate phase biases from interferogram of azimuth prefiltered SAR image pairs wil fail when there is no overlapped spectrum. The fringe simulation and maximum sharpness optimization are adopted to deal with the problems. Accordingly, a novel algorithm to coherently synthesize SAR images is presented. The experiment with the Terra SAR X-band （TerraSAR-X） satel ite data validates the performance of the presented method.展开更多
The excellent remote sensing ability of synthetic aperture radar(SAR)will be misled seriously when it encounters deceptive jamming which possesses high fidelity and fraudulence.In this paper,the dynamic synthetic aper...The excellent remote sensing ability of synthetic aperture radar(SAR)will be misled seriously when it encounters deceptive jamming which possesses high fidelity and fraudulence.In this paper,the dynamic synthetic aperture(DSA)scheme is used to extract the difference between the true and false targets.A simultaneous deceptive jamming suppression and target reconstruction method is proposed for a single channel SAR system to guarantee remote sensing ability.The system model is formulated as a sparse signal recovery problem with an unknown parametric dictionary to be estimated.An iterative reweighted method is employed to jointly handle the dictionary parameter learning and target reconstruction problem in an majorization-minimization framework,where a surrogate function majorizing the Gaussian entropy in the objective function is introduced to circumvent its non-convexity.After dictionary parameter learning,the grid mismatching problem in a fixed grid based method is avoided.Therefore,the proposed method can reap a super resolution result.Besides,a simple yet effective DSA section scheme is developed for the SAR data excerpting,in which only two DSAs are required.Experimental results about location error and reconstruction power error reveal that the proposed method is able to achieve a good performance in deceptive jamming suppression.展开更多
As digital image techniques have been widely used, the requirements for high-resolution images become increasingly stringent. Traditional single-frame interpolation techniques cannot add new high frequency information...As digital image techniques have been widely used, the requirements for high-resolution images become increasingly stringent. Traditional single-frame interpolation techniques cannot add new high frequency information to the expanded images, and cannot improve resolution in deed. Multiframe-based techniques are effective ways for high-resolution image reconstruction, but their computation complexities and the difficulties in achieving image sequences limit their applications. An original method using an artificial neural network is proposed in this paper. Using the inherent merits in neural network, we can establish the mapping between high frequency components in low-resolution images and high-resolution images. Example applications and their results demonstrated the images reconstructed by our method are aesthetically and quantitatively (using the criteria of MSE and MAE) superior to the images acquired by common methods. Even for infrared images this method can give satisfactory results with high definition. In addition, a single-layer linear neural network is used in this paper, the computational complexity is very low, and this method can be realized in real time.展开更多
A novel image restoration scheme, which is super-resolution image restoration algorithm Poisson-maximum-afterword-probability based on Markvo constraint (MPMAP) combined with evaluating image detail parameter D, has b...A novel image restoration scheme, which is super-resolution image restoration algorithm Poisson-maximum-afterword-probability based on Markvo constraint (MPMAP) combined with evaluating image detail parameter D, has been proposed. The advantage of super-resolution algorithm MPMAP incorporated with parameter D lies in the fact that super-resolution algorithm MPMAP model is discrete, which is in accordance with remote-sensing imaging model, and the algorithm MPMAP is proved applicable to linear and non-linear imaging models with a unique solution when noise is not severe. According to simulation experiments for practical images, super-resolution algorithm MPMAP can retain image details better than most of traditional restoration methods; at the same time, the proposed parameter D can help to identify real point spread function (PSF) value of degradation process. Processing result of practical remote-sensing images by MPMAP combined with parameter D are given, it illustrates that MPMAP restoration scheme combined PSF estimation has a better restoration result than that of Photoshop processing, based on the same original images. It is proved that the proposed scheme is helpful to offset the lack of resolution of the original remote-sensing images and has its extensive application foreground.展开更多
Sonar images have complex background, low contrast, and deteriorative edges; these characteristics make it difficult for researchers to dispose the sonar objects. The multi-resolution analysis represents the signals i...Sonar images have complex background, low contrast, and deteriorative edges; these characteristics make it difficult for researchers to dispose the sonar objects. The multi-resolution analysis represents the signals in different scales efficiently, which is widely used in image processing. Wavelets are successful in disposing point discontinuities in one dimension, but not in two dimensions. The finite Ridgelet transform （FRIT） deals efficiently with the singularity in high dimension. It presents three improved denoising approaches, which are based on FRIT and used in the sonar image disposal technique. By experiment and comparison with traditional methods, these approaches not only suppress the artifacts, but also obtain good effect in edge keeping and SNR of the sonar image denoising.展开更多
In the application of persistent scatterer interferometry(PSI),deformation information is extracted from persistent scatterer(PS)points.Thus,the density and position of PS points are critical for PSI.To increase the P...In the application of persistent scatterer interferometry(PSI),deformation information is extracted from persistent scatterer(PS)points.Thus,the density and position of PS points are critical for PSI.To increase the PS density,a time-series InSAR chain termed as"super-resolution persistent scatterer interferometry"(SR-PSI)is proposed.In this study,we investigate certain important properties of SR-PSI.First,we review the main workflow and dataflow of SR-PSI.It is shown that in the implementation of the Capon algorithm,the diagonal loading(DL)approach should be only used when the condition number of the covariance matrix is sufficiently high to reduce the discontinuities between the joint images.We then discuss the density and positioning accuracy of PS when compared with traditional PSI.The theory and experimental results indicate that SR-PSI can increase the PS density in urban areas.However,it is ineffective for the rural areas,which should be an important consideration for the engineering application of SR-PSI.Furthermore,we validate that the positioning accuracy of PS can be improved by SRPSI via simulations.展开更多
Nonparametric time-of-arrival（TOA） estimators for impulse radio ultra-wideband（IR-UWB） signals are proposed. Nonparametric detection is obviously useful in situations where detailed information about the statistic...Nonparametric time-of-arrival（TOA） estimators for impulse radio ultra-wideband（IR-UWB） signals are proposed. Nonparametric detection is obviously useful in situations where detailed information about the statistics of the noise is unavailable or not accurate. Such TOA estimators are obtained based on conditional statistical tests with only a symmetry distribution assumption on the noise probability density function. The nonparametric estimators are attractive choices for low-resolution IR-UWB digital receivers which can be implemented by fast comparators or high sampling rate low resolution analog-to-digital converters（ADCs）,in place of high sampling rate high resolution ADCs which may not be available in practice. Simulation results demonstrate that nonparametric TOA estimators provide more effective and robust performance than typical energy detection（ED） based estimators.展开更多
Aimed at the problem of classification of non-hydrocarbons of crude oil, the theoretical standpoint that the polarity of a compound depends on the whole structure and composition of molecule instead of a kind of heter...Aimed at the problem of classification of non-hydrocarbons of crude oil, the theoretical standpoint that the polarity of a compound depends on the whole structure and composition of molecule instead of a kind of heteroatom or its functional group was presented. A method was established for the systematically structural identification of nitric compounds in crude oil. The pre-fractionation of a crude oil sample into 7 fractions was performed by di- adsorption column chromatography with neutral aluminum oxide and silica gel. Subsequently, the individual components were obtained by using capillary column gas chromatography, and the types of compounds were detected by a mass spectrometer. In combination with a chemometric resolution, the compounds of fraction were further identified. This method can relieve the difficulty of classical analysis in identifying those species with very low contents or without being completely separated. The structures of 168 nitric compounds in a crude oil sample were determined by this method.展开更多
文摘This paper deals with the method of using quasi observation. In the paper a simple algorithm is developed for the adjustment computation with quasi observation at first. And then the ability of quasi observation to improve ambiguity search technique is studied in detail. The robustness of the method is also discussed. A method to determine the weight of quasi observation is proposed. The results show that a prior height can be taken as a quasi observation and used together with GPS observations. It can strengthen residual tests, especially in situation where there are fewer satellites in the sky. It also can change structure of incorrect solutions, which will theoretically make less incorrect solutions left in search space. At last the field tests are carried out to show that the proposed method is effective. The success rate of ambiguity resolution in the four field tests is improved significantly.
文摘For radar high resolution range profile (HRRP) recognition, three aspects are of great importance to improve the performance, i.e. discrimination for outlier, classification for inner and an accurate description for feature space. To tackle these issues, a novel target recognition method is designed, denoted by the multiple support vectors (multi-SV) method. With the proposed method, a special framework is constructed by a treble correlate support vector model to segment the feature space to two regions with the distribution of density, and then the description and classification hyperplane for each region are achieved. Based on the support vector framework, this method needs less memory and computation complexity to fit practical radar HRRP recognition. Finally, the experiment based on the measured data verifies the excellent performance of this method.
文摘It is an attractive method to combine GPS observations with the information from other surveying system to improve the ambiguity resolution. This research is conducted to investigate how to obtain the prior height information in bathymetric surveying by GPS positioning and how to use the prior height information and to obtain a robust result. The authors deal with the collection and the description of the prior height and the method using height validation to improve the ambiguity resolution. The principle of the method, the relationships between the height threshold and the ambiguity search space are presented. A method to determine the threshold for the height validation is suggested. The field tests are carried out to show the feasibility of the proposed methods.
基金supported by the National Natural Science Foundation of China (6087213461072117)
文摘Orthogonal frequency division multiplexing（OFDM） radar with multicarrier phase-coded waveforms has been recently introduced to achieve high range resolution.The conventional method for obtaining the high resolution range profile（HRRP） is based on matched filters.A method of synthesizing HRRP based on the fast Fourier transform（FFT） and decoding is proposed.The mathematical expressions of HRRP are derived by assuming an elementary scenario of point-scattering targets.Based on the characteristic of OFDM multicarrier signals,it mainly analyzes the influence on HRRP exerted by several factors,such as velocity compensation errors,the sampling frequency offset,and so on.The conclusions are significant for the design of the OFDM imaging radar.Finally,the simulation results demonstrate the validity of the conclusions.
文摘In a previous companion paper [1], the potential advantages of high resolution radar for improved target detection were introduced. In particular, the concept of shaping both the transmitted waveform and the receiving processor in accordance to the expected target down-range profile was highlighted and performance predictions were provided. In this paper, we present and evaluate an adaptive scheme devised to on-line estimate the target profile, in order to overcome a limited a-priori knowledge. In addition, we introduce a more general model of target impulse response, based on a statistical description, and we discuss the corresponding processing scheme and detection performance.
基金Project(21075138) supported by the National Natural Science Foundation of ChinaProject(cstc2011jjA0780) supported by Natural Science Foundation of Chongqing City,ChinaProject(KJ121311) supported by Educational Commission of Chongqing City of China
文摘The contents ofMg, Al, Si, Ti, Cr, Mn, Fe, Co, Cu, Ga, As, Se, Cd, Sb, Pb and Bi in high purity nickel were determined by high resolution inductively coupled plasma mass spectrometry （HR-ICP-MS）. The sample was dissolved in HNO3 and HCI by microwave digestion. Most of the spectral interferences could be avoided by measuring in the high resolution mode. The matrix effects because of the presence of excess HC1 and nickel were evaluated. Correction for matrix effects was made using Sc, Rh and T1 as internal standards. The optimum conditions for the determination were tested and discussed. The detection limits range from 0.012 to 1.76 ~tg/g depending on the type of elements. The applicability of the proposed method is also validated by the analysis of high purity nickel reference material （NIST SRM 671）. The relative standard deviation （RSD） is less than 3.3%. Results for determination of trace elements in high purity nickel were presented.
基金supported by the National Natural Science Foundation of China(42001297)the Research Foundation of Education Department of Hunan Province(19B061)the National Natural Science Foundation of Hunan Province(2021JJ40631)。
文摘In a global positioning system(GPS)passive radar,a high resolution requires a high sampling frequency,which increases the computational load.Balancing the computational load and the range resolution is challenging.This paper presents a method to trade off the range resolution and the computational load by experimentally determining the optimal sampling frequency through an analysis of multiple sets of GPS satellite data at different sampling frequencies.The test data are used to construct a range resolution-sampling frequency trade-off model using least-squares estimation.The theoretical analysis shows that the experimental data are the best fit using smoothing and nthorder derivative splines.Using field GPS C/A code signal-based GPS radar,the trade-off between the optimal sampling frequency is determined to be in the 20461.25–24553.5 kHz range,which supports a resolution of 43–48 m.Compared with the conventional method,the CPU time is reduced by approximately 50%.
基金supported by the National Natural Science Foundation of China(61271342)
文摘For a synthetic aperture radar（SAR） system mounted on a geostationary Earth orbit（GEO） satellite, the track can be curvilinear. Thus, a bistatic SAR system based up on geostationary transmitter and ＂receive-only＂ SAR system onboard airplanes, namely GEO spaceborne-airborne bistatic（GEO SA-Bi SAR）, is significantly different from the traditional bistatic SAR. This paper mainly studies the resolution characteristic of the sliding spotlight GEO SA-Bi SAR system. Firstly, the common azimuth coverage and coherent accumulated time are theoretically analyzed in detail. Then,based on the gradient method, the accurate two dimensional resolution of a GEO SA-Bi SAR system is analytically calculated. Finally, the simulation data show the correctness and effectiveness of the proposed resolution analysis method.
基金This project was supported by the National Natural Foundation of China (60404022) and the Foundation of Department ofEducation of Hebei Province (2002209).
文摘Mixture model based image segmentation method, which assumes that image pixels are independent and do not consider the position relationship between pixels, is not robust to noise and usually leads to misclassification. A new segmentation method, called multi-resolution Ganssian mixture model method, is proposed. First, an image pyramid is constructed and son-father link relationship is built between each level of pyramid. Then the mixture model segmentation method is applied to the top level. The segmentation result on the top level is passed top-down to the bottom level according to the son-father link relationship between levels. The proposed method considers not only local but also global information of image, it overcomes the effect of noise and can obtain better segmentation result. Experimental result demonstrates its effectiveness.
文摘Sparse representation has attracted extensive attention and performed well on image super-resolution（SR） in the last decade. However, many current image SR methods face the contradiction of detail recovery and artifact suppression. We propose a multi-resolution dictionary learning（MRDL） model to solve this contradiction, and give a fast single image SR method based on the MRDL model. To obtain the MRDL model, we first extract multi-scale patches by using our proposed adaptive patch partition method（APPM）. The APPM divides images into patches of different sizes according to their detail richness. Then, the multiresolution dictionary pairs, which contain structural primitives of various resolutions, can be trained from these multi-scale patches.Owing to the MRDL strategy, our SR algorithm not only recovers details well, with less jag and noise, but also significantly improves the computational efficiency. Experimental results validate that our algorithm performs better than other SR methods in evaluation metrics and visual perception.
基金supported by the National Natural Science Foundation of China(61271287)
文摘Based on the squint mode, a high resolution wide swath revisit synthetic aperture radar （SAR） imaging mode is pro- posed. The transmitting antennas are configured as the single phase center multiple azimuth beams （SPC MAB）. The formed two beams point to two different directions to obtain two images of the observed scenario. The receiving antennas are configured as displaced phase center multiple azimuth beams （DPC MAB） to decrease the required pulse repetition frequency （PRF）. The de- creased PRF can ensure the high resolution wide swath imaging. Based on the analysis of the character of the return signal, a pro- cessing method named multiple beam multiple channel algorithm （MBMCA） is proposed to separate the aliased sub-beams＇ echoes. The separated echoes are focused respectively to get the revisit imaging to the observed scenario. The simulation experiments ve- rify the validity and correctness of the proposed imaging mode and processing algorithm.
基金supported by the National Natural Science Foundationof China(41001282)
文摘The azimuth resolution improvement problem is solved via a coherent combination of synthetic aperture radar （SAR） ima-ges with the quasi-non-overlapped Doppler bandwidth. Prior to the spectra combination, SAR images should be coregistered, while phase biases induced by topography, atmospheric propagation delays and baseline measurement errors should be calibrated. However, the coregistration accuracy suffers from large Doppler decorrelation caused by the quasi-non-overlapped Doppler band-width. Furthermore, the method used to estimate phase biases from interferogram of azimuth prefiltered SAR image pairs wil fail when there is no overlapped spectrum. The fringe simulation and maximum sharpness optimization are adopted to deal with the problems. Accordingly, a novel algorithm to coherently synthesize SAR images is presented. The experiment with the Terra SAR X-band （TerraSAR-X） satel ite data validates the performance of the presented method.
基金supported in part by the National Natural Science Foundation of China under Grants 61801297,62171293,U1713217,U2033213,61971218,61801302,61701528,61601304in part by the National Science Fund for Distinguished Young Scholars under Grant 61925108+5 种基金in part by Natural Science Funding of Guangdong Province under Grant 2017A030313336in part by the Guangdong Basic and Applied Basic Research Foundation under Grant 2019A1515110509in part by Foundation of Shenzhen City under Grant JCYJ20170302142545828in part by the Shenzhen University Grant 2019119,2016057in part by the Fund of State Key Laboratory of Millimeter Waves under Grant K202235in part by Sichuan Science and Technology Program under Grant 2021YFS0319.
文摘The excellent remote sensing ability of synthetic aperture radar(SAR)will be misled seriously when it encounters deceptive jamming which possesses high fidelity and fraudulence.In this paper,the dynamic synthetic aperture(DSA)scheme is used to extract the difference between the true and false targets.A simultaneous deceptive jamming suppression and target reconstruction method is proposed for a single channel SAR system to guarantee remote sensing ability.The system model is formulated as a sparse signal recovery problem with an unknown parametric dictionary to be estimated.An iterative reweighted method is employed to jointly handle the dictionary parameter learning and target reconstruction problem in an majorization-minimization framework,where a surrogate function majorizing the Gaussian entropy in the objective function is introduced to circumvent its non-convexity.After dictionary parameter learning,the grid mismatching problem in a fixed grid based method is avoided.Therefore,the proposed method can reap a super resolution result.Besides,a simple yet effective DSA section scheme is developed for the SAR data excerpting,in which only two DSAs are required.Experimental results about location error and reconstruction power error reveal that the proposed method is able to achieve a good performance in deceptive jamming suppression.
文摘As digital image techniques have been widely used, the requirements for high-resolution images become increasingly stringent. Traditional single-frame interpolation techniques cannot add new high frequency information to the expanded images, and cannot improve resolution in deed. Multiframe-based techniques are effective ways for high-resolution image reconstruction, but their computation complexities and the difficulties in achieving image sequences limit their applications. An original method using an artificial neural network is proposed in this paper. Using the inherent merits in neural network, we can establish the mapping between high frequency components in low-resolution images and high-resolution images. Example applications and their results demonstrated the images reconstructed by our method are aesthetically and quantitatively (using the criteria of MSE and MAE) superior to the images acquired by common methods. Even for infrared images this method can give satisfactory results with high definition. In addition, a single-layer linear neural network is used in this paper, the computational complexity is very low, and this method can be realized in real time.
文摘A novel image restoration scheme, which is super-resolution image restoration algorithm Poisson-maximum-afterword-probability based on Markvo constraint (MPMAP) combined with evaluating image detail parameter D, has been proposed. The advantage of super-resolution algorithm MPMAP incorporated with parameter D lies in the fact that super-resolution algorithm MPMAP model is discrete, which is in accordance with remote-sensing imaging model, and the algorithm MPMAP is proved applicable to linear and non-linear imaging models with a unique solution when noise is not severe. According to simulation experiments for practical images, super-resolution algorithm MPMAP can retain image details better than most of traditional restoration methods; at the same time, the proposed parameter D can help to identify real point spread function (PSF) value of degradation process. Processing result of practical remote-sensing images by MPMAP combined with parameter D are given, it illustrates that MPMAP restoration scheme combined PSF estimation has a better restoration result than that of Photoshop processing, based on the same original images. It is proved that the proposed scheme is helpful to offset the lack of resolution of the original remote-sensing images and has its extensive application foreground.
基金This project was supported by the National Natural Science Foundation of China (60672034)the Research Fund for the Doctoral Program of Higher Education(20060217021)the Natural Science Foundation of Heilongjiang Province of China (ZJG0606-01)
文摘Sonar images have complex background, low contrast, and deteriorative edges; these characteristics make it difficult for researchers to dispose the sonar objects. The multi-resolution analysis represents the signals in different scales efficiently, which is widely used in image processing. Wavelets are successful in disposing point discontinuities in one dimension, but not in two dimensions. The finite Ridgelet transform （FRIT） deals efficiently with the singularity in high dimension. It presents three improved denoising approaches, which are based on FRIT and used in the sonar image disposal technique. By experiment and comparison with traditional methods, these approaches not only suppress the artifacts, but also obtain good effect in edge keeping and SNR of the sonar image denoising.
基金supported by the National Natural Science Foundation of China(62101284)the State Key Laboratory of Geo-Information Engineering and Key Laboratory of Surveying and Mapping Science and Geospatial Information Technology of Ministry of Natural Resources+4 种基金China Academy of Surveying and Mapping(2021-03-11)the Natural Science Project of Jiangsu Province(21KJB420003)Nanjing University of Posts and Telecommunications Start-up Fund(NY221033,NY220168)the Foundation of Jiangsu Province Shuangchuang Doctor Grant(JSSCBS20210543)Beijing Key Laboratory of Urban Spatial Information Engineering(20210215)。
文摘In the application of persistent scatterer interferometry(PSI),deformation information is extracted from persistent scatterer(PS)points.Thus,the density and position of PS points are critical for PSI.To increase the PS density,a time-series InSAR chain termed as"super-resolution persistent scatterer interferometry"(SR-PSI)is proposed.In this study,we investigate certain important properties of SR-PSI.First,we review the main workflow and dataflow of SR-PSI.It is shown that in the implementation of the Capon algorithm,the diagonal loading(DL)approach should be only used when the condition number of the covariance matrix is sufficiently high to reduce the discontinuities between the joint images.We then discuss the density and positioning accuracy of PS when compared with traditional PSI.The theory and experimental results indicate that SR-PSI can increase the PS density in urban areas.However,it is ineffective for the rural areas,which should be an important consideration for the engineering application of SR-PSI.Furthermore,we validate that the positioning accuracy of PS can be improved by SRPSI via simulations.
基金supported by the National High Technology Research and Development Program of China(863 Program)(2009AA011204)
文摘Nonparametric time-of-arrival（TOA） estimators for impulse radio ultra-wideband（IR-UWB） signals are proposed. Nonparametric detection is obviously useful in situations where detailed information about the statistics of the noise is unavailable or not accurate. Such TOA estimators are obtained based on conditional statistical tests with only a symmetry distribution assumption on the noise probability density function. The nonparametric estimators are attractive choices for low-resolution IR-UWB digital receivers which can be implemented by fast comparators or high sampling rate low resolution analog-to-digital converters（ADCs）,in place of high sampling rate high resolution ADCs which may not be available in practice. Simulation results demonstrate that nonparametric TOA estimators provide more effective and robust performance than typical energy detection（ED） based estimators.
文摘Aimed at the problem of classification of non-hydrocarbons of crude oil, the theoretical standpoint that the polarity of a compound depends on the whole structure and composition of molecule instead of a kind of heteroatom or its functional group was presented. A method was established for the systematically structural identification of nitric compounds in crude oil. The pre-fractionation of a crude oil sample into 7 fractions was performed by di- adsorption column chromatography with neutral aluminum oxide and silica gel. Subsequently, the individual components were obtained by using capillary column gas chromatography, and the types of compounds were detected by a mass spectrometer. In combination with a chemometric resolution, the compounds of fraction were further identified. This method can relieve the difficulty of classical analysis in identifying those species with very low contents or without being completely separated. The structures of 168 nitric compounds in a crude oil sample were determined by this method.
