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
High Resolution Wide Swath (HRWS) Synthetic Aperture Radar (SAR) often suffers from low Signal-to-Noise Ratio (SNR) due to small transmitting antenna, especially in phased array antenna systems. Digital Beam Forming (...High Resolution Wide Swath (HRWS) Synthetic Aperture Radar (SAR) often suffers from low Signal-to-Noise Ratio (SNR) due to small transmitting antenna, especially in phased array antenna systems. Digital Beam Forming (DBF) based on Single Input and Multiple Output (SIMO) achieves receiving array gain at the cost of increasing data rate. This letter proposes a new HRWS SAR method, which employs intra-pulse null steering to get receiving gain in elevation and decrease the data rate, and Multiple Input and Multiple Output (MIMO) using Space-Time Block Coding (STBC) in azimuth to get transmitting gain and receiving array gain simultaneously. The feasibility is verified by deduction and simulations.展开更多
Conventional synthetic aperture radar（SAR） systems cannot achieve both highresolution and wide-swath imaging simultaneously.This problem can be mitigated by employing multiple-azimuth-phases（MAPs） technology for s...Conventional synthetic aperture radar（SAR） systems cannot achieve both highresolution and wide-swath imaging simultaneously.This problem can be mitigated by employing multiple-azimuth-phases（MAPs） technology for spaceborne sliding spotlight SAR systems.However, traditional imaging algorithms have met challenges to process the data accurately, due to range model error, MAPs data reconstruction problem, high-order cross-coupling phase error and variation of Doppler parameters along the azimuth direction.Therefore, an improved imaging algorithm is proposed for solving the above problems.Firstly, a modified hyperbolic range equation（MHRE） is proposed by introducing a cubic term into the traditional hyperbolic range equation（THRE）.And two curved orbit correction methods are derived based on the proposed range model.Then, a MAPs sliding spotlight data reconstruction method is introduced, which solves the spectral aliasing problem by a de-rotation operation.Finally, high-order cross-coupling phases and variation of Doppler parameters are analyzed and the corresponding compensation methods are proposed.Simulation results for point-target scene are provided to verify the effectiveness of the proposed algorithm.展开更多
Optical imaging has served as a primary method to collect information about biosystems across scales—from functionalities of tissues to morphological structures of cells and even at biomolecular levels.However,to ade...Optical imaging has served as a primary method to collect information about biosystems across scales—from functionalities of tissues to morphological structures of cells and even at biomolecular levels.However,to adequately characterize a complex biosystem,an imaging system with a number of resolvable points,referred to as a space-bandwidth product(SBP),in excess of one billion is typically needed.Since a gigapixel-scale far exceeds the capacity of current optical imagers,compromises must be made to obtain either a low spatial resolution or a narrow field-of-view(FOV).The problem originates from constituent refractive optics—the larger the aperture,the more challenging the correction of lens aberrations.Therefore,it is impractical for a conventional optical imaging system to achieve an SBP over hundreds of millions.To address this unmet need,a variety of high-SBP imagers have emerged over the past decade,enabling an unprecedented resolution and FOV beyond the limit of conventional optics.We provide a comprehensive survey of high-SBP imaging techniques,exploring their underlying principles and applications in bioimaging.展开更多
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.
文摘High Resolution Wide Swath (HRWS) Synthetic Aperture Radar (SAR) often suffers from low Signal-to-Noise Ratio (SNR) due to small transmitting antenna, especially in phased array antenna systems. Digital Beam Forming (DBF) based on Single Input and Multiple Output (SIMO) achieves receiving array gain at the cost of increasing data rate. This letter proposes a new HRWS SAR method, which employs intra-pulse null steering to get receiving gain in elevation and decrease the data rate, and Multiple Input and Multiple Output (MIMO) using Space-Time Block Coding (STBC) in azimuth to get transmitting gain and receiving array gain simultaneously. The feasibility is verified by deduction and simulations.
基金supported by the National Natural Science Foundation of China (No.61132006)
文摘Conventional synthetic aperture radar（SAR） systems cannot achieve both highresolution and wide-swath imaging simultaneously.This problem can be mitigated by employing multiple-azimuth-phases（MAPs） technology for spaceborne sliding spotlight SAR systems.However, traditional imaging algorithms have met challenges to process the data accurately, due to range model error, MAPs data reconstruction problem, high-order cross-coupling phase error and variation of Doppler parameters along the azimuth direction.Therefore, an improved imaging algorithm is proposed for solving the above problems.Firstly, a modified hyperbolic range equation（MHRE） is proposed by introducing a cubic term into the traditional hyperbolic range equation（THRE）.And two curved orbit correction methods are derived based on the proposed range model.Then, a MAPs sliding spotlight data reconstruction method is introduced, which solves the spectral aliasing problem by a de-rotation operation.Finally, high-order cross-coupling phases and variation of Doppler parameters are analyzed and the corresponding compensation methods are proposed.Simulation results for point-target scene are provided to verify the effectiveness of the proposed algorithm.
基金supported partially by the National Institutes of Health(R01EY029397,R35GM128761)the National Science Foundation(1652150)+1 种基金support from the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(2019R1A6A3A03031505)support from the National Science Foundation(1846784)。
文摘Optical imaging has served as a primary method to collect information about biosystems across scales—from functionalities of tissues to morphological structures of cells and even at biomolecular levels.However,to adequately characterize a complex biosystem,an imaging system with a number of resolvable points,referred to as a space-bandwidth product(SBP),in excess of one billion is typically needed.Since a gigapixel-scale far exceeds the capacity of current optical imagers,compromises must be made to obtain either a low spatial resolution or a narrow field-of-view(FOV).The problem originates from constituent refractive optics—the larger the aperture,the more challenging the correction of lens aberrations.Therefore,it is impractical for a conventional optical imaging system to achieve an SBP over hundreds of millions.To address this unmet need,a variety of high-SBP imagers have emerged over the past decade,enabling an unprecedented resolution and FOV beyond the limit of conventional optics.We provide a comprehensive survey of high-SBP imaging techniques,exploring their underlying principles and applications in bioimaging.
