Multi-temporal synthetic aperture radar interferometry(MT-InSAR)is a standard technique for mapping clustering and wide-scale deformation.A linear model is often used in phase unwrapping to overcome the underdetermina...Multi-temporal synthetic aperture radar interferometry(MT-InSAR)is a standard technique for mapping clustering and wide-scale deformation.A linear model is often used in phase unwrapping to overcome the underdetermination.It’s difficult to identify different types of nonlinear deformation.However,the interpretation of nonlinear deformation is very important in monitoring potential risk.This paper introduces a comprehensive approach for identifying and interpreting different types of deformation within InSAR datasets,integrating initial clustering and classification simplification.Initial classification is performed using the K-means clustering method to cluster the collected InSAR deformation time-series data.Then we use F test and Anderson-Darling test(AD test)to simplify the clusters after initial classification.This technique distinctly discerns the changing trends of deformation signals,thereby providing robust support for interpreting potential deformation scenarios within observed InSAR regions.展开更多
This paper studies large-scale multi-input multi-output(MIMO)orthogonal frequency division multiplexing(OFDM)communications in a broadband frequency-selective channel,where a massive MIMO base station(BS)communicates ...This paper studies large-scale multi-input multi-output(MIMO)orthogonal frequency division multiplexing(OFDM)communications in a broadband frequency-selective channel,where a massive MIMO base station(BS)communicates with multiple users equipped with multi-antenna.We develop a hybrid precoding design to maximize the weighted sum-rate(WSR)of the users by optimizing the digital and the analog precoders alternately.For the digital part,we employ block-diagonalization to eliminate inter-user interference and apply water-filling power allocation to maximize the WSR.For the analog part,the optimization of the PSN is formulated as an unconstrained problem,which can be efficiently solved by a gradient descent method.Numerical results show that the proposed block-diagonal hybrid precoding algorithm can outperform the existing works.展开更多
In addition to conventional antenna-based array,the reconfigurable intelligent surface(RIS)holds promise as an alternative technology for manufacturing massive multi-input multi-output(MIMO)array for beyond 5G communi...In addition to conventional antenna-based array,the reconfigurable intelligent surface(RIS)holds promise as an alternative technology for manufacturing massive multi-input multi-output(MIMO)array for beyond 5G communications.This paper designs a fast algorithm to optimize the RIS-based MIMO precoder for maximizing the spectral efficiency,which includes the digital precoder and the RIS reflection phases.We evaluate the optimality of the algorithm by deriving an RIS channel capacity upper bound utilizing majorization theory.Our scheme can work for an RIS in both frequency flat and frequency selective channels,with either continuously or discretely tunable phases.The simulation results show that the proposed algorithm can achieve the capacity upper bound in some scenarios,which empirically proves its optimality.It is also shown that our algorithm is one-to-two orders of magnitude faster than the state-of-the-art methods in the literature.展开更多
Visible-light communication(VLC)stands as a promising component of the future communication network by providing high-capacity,low-latency,and high-security wireless communication.Superluminescent diode(SLD)is propose...Visible-light communication(VLC)stands as a promising component of the future communication network by providing high-capacity,low-latency,and high-security wireless communication.Superluminescent diode(SLD)is proposed as a new light emitter in the VLC system due to its properties of droop-free emission,high optical power density,and low speckle-noise.In this paper,we analyze a VLC system based on SLD,demonstrating effective implementation of carrierless amplitude and phase modulation(CAP).We create a low-complexity memory-polynomial-aided neural network(MPANN)to replace the traditional finite impulse response(FIR)post-equalization filters of CAP,leading to significant mitigation of the linear and nonlinear distortion of the VLC channel.The MPANN shows a gain in Q factor of up to 2.7 dB higher than other equalizers,and more than four times lower complexity than a standard deep neural network(DNN),hence,the proposed MPANN opens a pathway for the next generation of robust and efficient neural network equalizers in VLC.We experimentally demonstrate a proof-of-concept 2.95-Gbit/s transmission using MPANN-aided CAP with 16-quadrature amplitude modulation(16-QAM)through a 30-cm channel based on the 442-nm blue SLD emitter.展开更多
Synthetic aperture radar(SAR)is able to acquire high-resolution method using the active microwave imaging method.SAR images are widely used in target recognition,classification,and surface analysis,with extracted feat...Synthetic aperture radar(SAR)is able to acquire high-resolution method using the active microwave imaging method.SAR images are widely used in target recognition,classification,and surface analysis,with extracted features.Attribute scattering center(ASC)is able to describe the image features for these tasks.However,sidelobe effects reduce the accuracy and reliability of the estimated ASC model parameters.This paper incorporates the SAR super-resolution into the ASC extraction to improve its performance.Both filter bank and subspace methods are demonstrated for preprocessing to supress the sidelobe.Based on the preprocessed data,a reinforcement based ASC method is used to get the parameters.The experimental results show that the super-resolution method can reduce noise and suppress sidelobe effect,which improve accuracy of the estimated ASC model parameters.展开更多
In this Letter,we propose and experimentally demonstrate a lens-free wavefront shaping method that utilizes synchronized signal block beam alignment and a genetic algorithm(SSBGA)for a diffuse non-line-of-sight(NLOS)v...In this Letter,we propose and experimentally demonstrate a lens-free wavefront shaping method that utilizes synchronized signal block beam alignment and a genetic algorithm(SSBGA)for a diffuse non-line-of-sight(NLOS)visible light communication(VLC)system.The proposed method effectively controls the position and mobility of visible light beams by partitioning spatial light modulator pixels and manipulating beams to converge at distinct spatial positions,thereby enhancing wavefront shaping efficiency,which achieves a significant 23.9 dB optical power enhancement at+2 mm offset,surpassing the lens-based continuous sequence(CS)scheme by 21.7 dB.At+40°angle,the improvement reaches up to 11.8 dB and 16.8 dB compared to the results with and without lens-based CS,respectively.A maximum rate of 5.16 Gbps is successfully achieved using bit-power loading discrete multi-tone(DMT)modulation and the proposed SSBGA in an NLOS VLC system,which outperforms the lens-based CS by 1.07 Gbps and obtains a power saving of 55.6%during the transmission at4 Gbps.To the best of our knowledge,this is the first time that high-speed communication has been realized in an NLOS VLC system without a lens.展开更多
This paper builds a binary tree for the target based on the bounding volume hierarchy technology,thereby achieving strict acceleration of the shadow judgment process and reducing the computational complexity from the ...This paper builds a binary tree for the target based on the bounding volume hierarchy technology,thereby achieving strict acceleration of the shadow judgment process and reducing the computational complexity from the original O(N^(3))to O(N^(2)logN).Numerical results show that the proposed method is more efficient than the traditional method.It is verified in multiple examples that the proposed method can complete the convergence of the current.Moreover,the proposed method avoids the error of judging the lit-shadow relationship based on the normal vector,which is beneficial to current iteration and convergence.Compared with the brute force method,the current method can improve the simulation efficiency by 2 orders of magnitude.The proposed method is more suitable for scattering problems in electrically large cavities and complex scenarios.展开更多
Based on an analog radio frequency(RF)network,hybrid precoding(HPC)for massive MIMO can achieve very high spectral efficiencies with moderate hardware cost and power consumption.Despite the extensive research efforts ...Based on an analog radio frequency(RF)network,hybrid precoding(HPC)for massive MIMO can achieve very high spectral efficiencies with moderate hardware cost and power consumption.Despite the extensive research efforts in recent years,the practioners are still looking for HPCs that are efficient and easy-to-implement.In this paper,we present a new method termed as the universal hybrid precoding(UHP),which is nearly optimal,computationally efficient,and applicable to various types of RF network(thus,the name universal):the components of the network can be phase shifters(with finite or infinite resolutions),switches,or their combinations;the topology of the network can be fully-connected or partiallyconnected.Besides the standard UHP,we also propose a simplified version termed as sUHP to trade a negligible performance loss for much reduced computational complexity.The analysis shows that the computational complexity of the proposed UHP/sUHP is one to two orders of magnitude lower than the state-of-theart methods.Simulation results verify the(near-)optimality of the proposed UHP scheme for various forms of the analog networks.展开更多
HF (high frequency) radar sounder technology has been developed for several missions of Mars surface/subsurface exploration. This paper presents a model of rough surface and stratified sub-surfaces to describe the mul...HF (high frequency) radar sounder technology has been developed for several missions of Mars surface/subsurface exploration. This paper presents a model of rough surface and stratified sub-surfaces to describe the multi-layer structure of Mars polar deposits. Based on numerical simulation of radar echoes from rough surface/stratified interfaces, an inversion approach is developed to obtain the parameters of Polar Layered Deposits, i.e. layers thickness and dielectric constants. As a validation example, the SHARAD radar sounder data of the Promethei Lingula of Mars South Polar region is adopted for parameters inversion. The result of stratification is also analyzed and compared with the optical photo of the deep cliff of Chasma Australe canyon. Dielectric inversions show that the deposit media are not uniform, and the dielectric constants of the Promethei Lingula surfaces are large, and become reduced around the depth of 20 m - 30 m, below where most of the deposits are nearly pure ice, except a few thin layers with a lot of dust.展开更多
We successfully demonstrate 32-Gbaud Probabilistically Shaped 4096-ary Quadrature Amplitude Modulation(PS-4096QAM)TeraHertz(THz)signal wired transmission at 325 GHz over the 1-m Hollow-Core Fiber(HCF)in a photon-assis...We successfully demonstrate 32-Gbaud Probabilistically Shaped 4096-ary Quadrature Amplitude Modulation(PS-4096QAM)TeraHertz(THz)signal wired transmission at 325 GHz over the 1-m Hollow-Core Fiber(HCF)in a photon-assisted THz-wave communication system.By employing advanced Digital Signal Processing(DSP)and the PS technique,the 352-Gbit/s line rate(288-Gbit/s net rate)delivery with a net Spectral Efficiency(SE)of 9 bit/s/Hz is realized in the experiment,satisfying the 0.86-Normalized Generalized Mutual Information(NGMI)Low-Density Parity-Check(LDPC)threshold.展开更多
Unmanned aerial vehicle(UAV)array InSAR is a new type of single-flight 3D SAR imaging system with the advantages of high coherence and resolution.However,due to the low altitude of the platform,the elevation ambiguity...Unmanned aerial vehicle(UAV)array InSAR is a new type of single-flight 3D SAR imaging system with the advantages of high coherence and resolution.However,due to the low altitude of the platform,the elevation ambiguity of the system is smaller than the maximal terrain elevation.Since the spatial phase unwrapping is conducted based on the assumption of phase continuity,the inappropriate ambiguity will cause significant unwrapping errors.In this work,a 3D phase unwrapping algorithm assisted by image segmentation is proposed to address this issue.The Markov random field(MRF)is utilized for image segmentation.The optimal spatial phase unwrapping network is achieved based on the segmentation results.The asymptotic 3D phase unwrapping is adopted to get the refined 3D reconstruction.Results based on the real airborne array-InSAR data show that the proposed method effectively improves the elevation ambiguity.展开更多
This year,the global data traffic will grow up to 4.8 zettabytes annually,which is 11 times more than all data traffic generated in 2012 (437 exabytes)[1].The huge data traffic is mainly caused by video-intensive serv...This year,the global data traffic will grow up to 4.8 zettabytes annually,which is 11 times more than all data traffic generated in 2012 (437 exabytes)[1].The huge data traffic is mainly caused by video-intensive services,such as Internetof-Things (IoT),4 K/8 K videos.The high capacity and bandwidth requirement from the transport network to the core is a major challenge in the 5G network.Therefore,the millimeter wave (MMW) with a much wider bandwidth is a very important backhaul solution [2,3].展开更多
Due to limited antenna space,high communication requirements,and strict regulatory constraints,the design of antennas for modern mobile phones has become an exceedingly challenging task.In recent years,numerous studie...Due to limited antenna space,high communication requirements,and strict regulatory constraints,the design of antennas for modern mobile phones has become an exceedingly challenging task.In recent years,numerous studies have been conducted in this area,leading to significant advancements.This review paper comprehensively summarizes recent progress made in antenna design for modern mobile phones.Firstly,the challenges faced in antenna design for modern mobile phones are described,including bandwidth enhancement,integration and decoupling techniques,mm-wave array antennas,satellite communication antennas,as well as interactions between mobile antennas and the human body.Secondly,the basic antenna types(such as inverted-F,slot,loop,and planar inverted-F antennas)commonly used in modern metal-bezel mobile phones along with their key characteristics are briefly summarized.Thirdly,the commonly exployed methods used in practical applications for designing wideband antennas within compact sizes and achieving decoupling among multiple antennas with wide bandwidths are collected.Fourthly,recent advances in the design of compact,wideband,and wide-angle scanning mm-wave arrays for modern mobile phones are summarized.Fifthly,recent progress made in satellite communication antenna designs for modern mobile phones,including broadside and end-fire radiation patterns,is presented.Sixthly,recent studies on the interaction between mobile antennas and the human body are briefly concluded.Finally,the future challenge of antenna design for mobile phones is briefly discussed.It is our hope that this comprehensive review will provide readers with a systematic understanding of antenna design principles applicable to modern mobile phones.展开更多
This Letter proposes a post-equalizer for underwater visible light communication(UVLC) systems that combines channel estimation and joint time-frequency analysis, named channel-estimation-based bandpass variable-order...This Letter proposes a post-equalizer for underwater visible light communication(UVLC) systems that combines channel estimation and joint time-frequency analysis, named channel-estimation-based bandpass variable-order time-frequency network(CBV-TFNet). By utilizing a bandpass variable-order loss function with communication prior knowledge, CBVTFNet enhances communication performance and training stability. It enables lightweight implementation and faster convergence through a channel estimation-based mask. The superior performance of the proposed equalization method over Volterra and deep neural network(DNN)-based methods has been studied experimentally. Using bit-power loading discrete multitone (DMT) modulation, the proposed method achieves a transmission bitrate of 4.956 Gbps through a 1.2 m underwater channel utilizing only 38.15% of real multiplication calculations compared to the DNN equalizer and achieving a bitrate gain of440 Mbps and a significantly larger dynamic range over the LMS-Volterra equalizer. Results highlight CBV-TFNet's potential for future post-equalization in UVLC systems.展开更多
This paper reports a photonics-assisted millimeter-wave (mm-wave) joint radar jamming and secure communication system constructed through a photonic upconversion technique. In the experiments, a 30 GHz constant envelo...This paper reports a photonics-assisted millimeter-wave (mm-wave) joint radar jamming and secure communication system constructed through a photonic upconversion technique. In the experiments, a 30 GHz constant envelope linear frequency-modulated orthogonal frequency division modulation(CE-LFM-OFDM) signal with an instantaneous bandwidth of 1 GHz is synthesized by encoding 1 GBaud encrypted 16-quadrature amplitude modulation(16-QAM) OFDM signal. The velocity deception jamming is achieved with a spurious suppression ratio over 30 dB. Furthermore, we efficiently execute range deception jamming with a time shift of 10 ns. Simultaneously, the encrypted 16-QAM OFDM signal is successfully transmitted over a 1.2 m wireless link, with a data rate of 4 Gbit/s.展开更多
Miniaturized fiber-optic magnetic field sensors have attracted considerable interest owing to their superiorities in anti-electromagnetic interference and compactness.However,the intrinsic thermodynamic properties of ...Miniaturized fiber-optic magnetic field sensors have attracted considerable interest owing to their superiorities in anti-electromagnetic interference and compactness.However,the intrinsic thermodynamic properties of the material make temperature cross-sensitivity a challenging problem in terms of sensing accuracy and reliability.In this study,an ultracompact multicore fiber(MCF)tip sensor was designed to discriminatively measure the magnetic field and temperature,which was subsequently evaluated experimentally.The novel 3D printed sensing component consists of a bowl-shaped microcantilever and a polymer microfluid-infiltrated microcavity on the end-facet of an MCF,acting as two miniaturized Fabry-Perot interferometers.The magnetic sensitivity of the microcantilever was implemented by incorporating an iron micro ball into the microcantilever,and the microfluid-infiltrated microcavity enhanced the capability of highly sensitive temperature sensing.Using this tiny fiber-facet device in the two channels of an MCF allows discriminative measurements of the magnetic field and temperature by determining the sensitivity coefficient matrix of two parameters.The device exhibited a high magnetic field intensity sensitivity,approximately 1805.6 pm/mT with a fast response time of~213 ms and a high temperature sensitivity of 160.3 pm/℃.Moreover,the sensor had a low condition number of 11.28,indicating high reliability in two-parameter measurements.The proposed 3D printed MCF-tip probes,which detect multiple signals through multiple channels within a single fiber,can provide an ultracompact,sensitive,and reliable scheme for discriminative measurements.The bowl-shaped microcantilever also provides a useful platform for incorporating microstructures with functional materials,extending multi-parameter sensing scenarios and promoting the application of MCFs.展开更多
Light-emitting diode(LED)-based visible light communication(VLC) has become a potential candidate for nextgeneration ultra-high-speed indoor wireless communication. In this paper, four special-shaped 8-quadrature ampl...Light-emitting diode(LED)-based visible light communication(VLC) has become a potential candidate for nextgeneration ultra-high-speed indoor wireless communication. In this paper, four special-shaped 8-quadrature amplitude modulation(QAM) constellations are investigated in a single-carrier VLC system. It is numerically verified and experimentally demonstrated that circular(7,1) shows obvious superiority in the performance of the dynamic range of signal voltage peak-to-peak(vpp) value and bit error rate(BER). Next best is rectangular, followed by triangular; circular(4,4) has the worst performance. A data rate of 1.515 Gbit/s is successfully achieved by circular(7,1) employing a red chip LED over 0.5 m indoor free space transmission below a BER threshold of3.8 × 10^(-3). Compared with circular(4,4), the traditional 8-QAM constellation, circular(7,1) provides a wider dynamic range of signal vpp, a higher data rate, and a longer transmission distance. To the best of our knowledge,this is the first investigation into the performance differences of special-shaped 8-QAM constellations in a highspeed, single-carrier VLC system, and the results comprehensively demonstrate that circular(7,1) is the optimal option.展开更多
Asymmetrically clipped optical orthogonal frequency division multiplexing(ACO-OFDM)has been a promising candidate in visible light communications(VLC)due to its improvement in power efficiency and reduction of nonline...Asymmetrically clipped optical orthogonal frequency division multiplexing(ACO-OFDM)has been a promising candidate in visible light communications(VLC)due to its improvement in power efficiency and reduction of nonlinearity based on previous simulation analysis.In this paper,for the first time as far as we know,we experimentally verify that ACO-OFDM would be an efficient scheme to improve the performance of a gigabit wavelength division multiplexing VLC system.Our theoretical investigations reveal that the advantages of ACO-OFDM can be attributed to the reduction of inter-carrier interference caused by signal–signal beating noise.An aggregate data rate of 1.05 Gb∕s is successfully achieved over 30 cm transmission below the 7%forwarderror-correction threshold of 3.8×10−3.The experimental results show that ACO-OFDM can outperform DC-biased optical OFDM by BER performance of 1.5 dB at the same data rate and 4 dB at the same bandwidth,which clearly demonstrates the benefit and feasibility of ACO-OFDM.展开更多
The interactions between electrons and phonons play the key role in determining the carrier transport properties in semiconductors.In this work,comprehensive investigations on full electron–phonon(el–ph)couplings an...The interactions between electrons and phonons play the key role in determining the carrier transport properties in semiconductors.In this work,comprehensive investigations on full electron–phonon(el–ph)couplings and their influences on carrier mobility and thermoelectric(TE)performances of 2D group IV and V elemental monolayers are performed,and we also analyze the selection rules on el–ph couplings using group theory.For shallow n/p-dopings in Si,Ge,and Sn,ZA/TA/LO phonon modes dominate the intervalley scatterings.Similarly strong intervalley scatterings via ZA/TO phonon modes can be identified for CBM electrons in P,As,and Sb,and for VBM holes,ZA/TA phonon modes dominate intervalley scatterings in P while LA phonons dominate intravalley scatterings in As and Sb.By considering full el–ph couplings,the TE performance for these two series of monolayers are predicted,which seriously downgrades the thermoelectric figures of merits compared with those predicted by the constant relaxation time approximation.展开更多
Wavelength division multiplexing(WDM)and space division multiplexing(SDM)based on few-mode fiber(FMF)and multi-core fiber(MCF)have been vigorously developed to increase the transmission capacity of optical communicati...Wavelength division multiplexing(WDM)and space division multiplexing(SDM)based on few-mode fiber(FMF)and multi-core fiber(MCF)have been vigorously developed to increase the transmission capacity of optical communication networks[1–5].However,the mode crosstalk generated in the mode division multiplexing(MDM)system causes the correlation between different mode signals,which seriously damages the transmission performance.Therefore,an effective multiple-input-multiple-output(MIMO)time domain or frequency domain equalizer should be used to eliminate the crosstalk between different mode signals.展开更多
基金supported in part by the National Natural Foundation of China(No.62201158).
文摘Multi-temporal synthetic aperture radar interferometry(MT-InSAR)is a standard technique for mapping clustering and wide-scale deformation.A linear model is often used in phase unwrapping to overcome the underdetermination.It’s difficult to identify different types of nonlinear deformation.However,the interpretation of nonlinear deformation is very important in monitoring potential risk.This paper introduces a comprehensive approach for identifying and interpreting different types of deformation within InSAR datasets,integrating initial clustering and classification simplification.Initial classification is performed using the K-means clustering method to cluster the collected InSAR deformation time-series data.Then we use F test and Anderson-Darling test(AD test)to simplify the clusters after initial classification.This technique distinctly discerns the changing trends of deformation signals,thereby providing robust support for interpreting potential deformation scenarios within observed InSAR regions.
基金supported by National Natural Science Foundation of China(No.61771005)
文摘This paper studies large-scale multi-input multi-output(MIMO)orthogonal frequency division multiplexing(OFDM)communications in a broadband frequency-selective channel,where a massive MIMO base station(BS)communicates with multiple users equipped with multi-antenna.We develop a hybrid precoding design to maximize the weighted sum-rate(WSR)of the users by optimizing the digital and the analog precoders alternately.For the digital part,we employ block-diagonalization to eliminate inter-user interference and apply water-filling power allocation to maximize the WSR.For the analog part,the optimization of the PSN is formulated as an unconstrained problem,which can be efficiently solved by a gradient descent method.Numerical results show that the proposed block-diagonal hybrid precoding algorithm can outperform the existing works.
基金supported by National Natural Science Foundation of China Grant No.61771005。
文摘In addition to conventional antenna-based array,the reconfigurable intelligent surface(RIS)holds promise as an alternative technology for manufacturing massive multi-input multi-output(MIMO)array for beyond 5G communications.This paper designs a fast algorithm to optimize the RIS-based MIMO precoder for maximizing the spectral efficiency,which includes the digital precoder and the RIS reflection phases.We evaluate the optimality of the algorithm by deriving an RIS channel capacity upper bound utilizing majorization theory.Our scheme can work for an RIS in both frequency flat and frequency selective channels,with either continuously or discretely tunable phases.The simulation results show that the proposed algorithm can achieve the capacity upper bound in some scenarios,which empirically proves its optimality.It is also shown that our algorithm is one-to-two orders of magnitude faster than the state-of-the-art methods in the literature.
基金the National Key Research,Development Program of China(2017YFB0403603)the NSFC project(No.61925104).JAHL,YM,TKN and BSO gratefully acknowledge the financial support from King Abdullah University of Science and Technology(KAUST)through BAS/1/1614-01-01,REP/1/2878-01-01,GEN/1/6607-01-01,and KCR/1/2081-01-01the King Abdullah University of Science and Technology(KAUST)Office of Sponsored Research(OSR)under Award No.OSR-CRG2017-3417.JAHL further acknowledge access to the KAUST Nanofabrication Core Lab for the fabrication of devices.
文摘Visible-light communication(VLC)stands as a promising component of the future communication network by providing high-capacity,low-latency,and high-security wireless communication.Superluminescent diode(SLD)is proposed as a new light emitter in the VLC system due to its properties of droop-free emission,high optical power density,and low speckle-noise.In this paper,we analyze a VLC system based on SLD,demonstrating effective implementation of carrierless amplitude and phase modulation(CAP).We create a low-complexity memory-polynomial-aided neural network(MPANN)to replace the traditional finite impulse response(FIR)post-equalization filters of CAP,leading to significant mitigation of the linear and nonlinear distortion of the VLC channel.The MPANN shows a gain in Q factor of up to 2.7 dB higher than other equalizers,and more than four times lower complexity than a standard deep neural network(DNN),hence,the proposed MPANN opens a pathway for the next generation of robust and efficient neural network equalizers in VLC.We experimentally demonstrate a proof-of-concept 2.95-Gbit/s transmission using MPANN-aided CAP with 16-quadrature amplitude modulation(16-QAM)through a 30-cm channel based on the 442-nm blue SLD emitter.
基金supported by the National Natural Foundation of China(No.62201158).
文摘Synthetic aperture radar(SAR)is able to acquire high-resolution method using the active microwave imaging method.SAR images are widely used in target recognition,classification,and surface analysis,with extracted features.Attribute scattering center(ASC)is able to describe the image features for these tasks.However,sidelobe effects reduce the accuracy and reliability of the estimated ASC model parameters.This paper incorporates the SAR super-resolution into the ASC extraction to improve its performance.Both filter bank and subspace methods are demonstrated for preprocessing to supress the sidelobe.Based on the preprocessed data,a reinforcement based ASC method is used to get the parameters.The experimental results show that the super-resolution method can reduce noise and suppress sidelobe effect,which improve accuracy of the estimated ASC model parameters.
基金supported by the National Key Research and Development Program of China(No.2022YFB2802803)the National Natural Science Foundation of China(Nos.61925104,62031011,and 62201157)。
文摘In this Letter,we propose and experimentally demonstrate a lens-free wavefront shaping method that utilizes synchronized signal block beam alignment and a genetic algorithm(SSBGA)for a diffuse non-line-of-sight(NLOS)visible light communication(VLC)system.The proposed method effectively controls the position and mobility of visible light beams by partitioning spatial light modulator pixels and manipulating beams to converge at distinct spatial positions,thereby enhancing wavefront shaping efficiency,which achieves a significant 23.9 dB optical power enhancement at+2 mm offset,surpassing the lens-based continuous sequence(CS)scheme by 21.7 dB.At+40°angle,the improvement reaches up to 11.8 dB and 16.8 dB compared to the results with and without lens-based CS,respectively.A maximum rate of 5.16 Gbps is successfully achieved using bit-power loading discrete multi-tone(DMT)modulation and the proposed SSBGA in an NLOS VLC system,which outperforms the lens-based CS by 1.07 Gbps and obtains a power saving of 55.6%during the transmission at4 Gbps.To the best of our knowledge,this is the first time that high-speed communication has been realized in an NLOS VLC system without a lens.
基金the National Natural Science Foundation of China under Grants No.62231021 and No.92373201.
文摘This paper builds a binary tree for the target based on the bounding volume hierarchy technology,thereby achieving strict acceleration of the shadow judgment process and reducing the computational complexity from the original O(N^(3))to O(N^(2)logN).Numerical results show that the proposed method is more efficient than the traditional method.It is verified in multiple examples that the proposed method can complete the convergence of the current.Moreover,the proposed method avoids the error of judging the lit-shadow relationship based on the normal vector,which is beneficial to current iteration and convergence.Compared with the brute force method,the current method can improve the simulation efficiency by 2 orders of magnitude.The proposed method is more suitable for scattering problems in electrically large cavities and complex scenarios.
基金supported by National Natural Science Foundation of China Grant No. 61771005
文摘Based on an analog radio frequency(RF)network,hybrid precoding(HPC)for massive MIMO can achieve very high spectral efficiencies with moderate hardware cost and power consumption.Despite the extensive research efforts in recent years,the practioners are still looking for HPCs that are efficient and easy-to-implement.In this paper,we present a new method termed as the universal hybrid precoding(UHP),which is nearly optimal,computationally efficient,and applicable to various types of RF network(thus,the name universal):the components of the network can be phase shifters(with finite or infinite resolutions),switches,or their combinations;the topology of the network can be fully-connected or partiallyconnected.Besides the standard UHP,we also propose a simplified version termed as sUHP to trade a negligible performance loss for much reduced computational complexity.The analysis shows that the computational complexity of the proposed UHP/sUHP is one to two orders of magnitude lower than the state-of-theart methods.Simulation results verify the(near-)optimality of the proposed UHP scheme for various forms of the analog networks.
文摘HF (high frequency) radar sounder technology has been developed for several missions of Mars surface/subsurface exploration. This paper presents a model of rough surface and stratified sub-surfaces to describe the multi-layer structure of Mars polar deposits. Based on numerical simulation of radar echoes from rough surface/stratified interfaces, an inversion approach is developed to obtain the parameters of Polar Layered Deposits, i.e. layers thickness and dielectric constants. As a validation example, the SHARAD radar sounder data of the Promethei Lingula of Mars South Polar region is adopted for parameters inversion. The result of stratification is also analyzed and compared with the optical photo of the deep cliff of Chasma Australe canyon. Dielectric inversions show that the deposit media are not uniform, and the dielectric constants of the Promethei Lingula surfaces are large, and become reduced around the depth of 20 m - 30 m, below where most of the deposits are nearly pure ice, except a few thin layers with a lot of dust.
基金supported by National Key R&D Program of China(2018YFB1800900)National Natural Science Foundation of China(61935005,91938202,61720106015,61835002,61805043,62127802).
文摘We successfully demonstrate 32-Gbaud Probabilistically Shaped 4096-ary Quadrature Amplitude Modulation(PS-4096QAM)TeraHertz(THz)signal wired transmission at 325 GHz over the 1-m Hollow-Core Fiber(HCF)in a photon-assisted THz-wave communication system.By employing advanced Digital Signal Processing(DSP)and the PS technique,the 352-Gbit/s line rate(288-Gbit/s net rate)delivery with a net Spectral Efficiency(SE)of 9 bit/s/Hz is realized in the experiment,satisfying the 0.86-Normalized Generalized Mutual Information(NGMI)Low-Density Parity-Check(LDPC)threshold.
文摘Unmanned aerial vehicle(UAV)array InSAR is a new type of single-flight 3D SAR imaging system with the advantages of high coherence and resolution.However,due to the low altitude of the platform,the elevation ambiguity of the system is smaller than the maximal terrain elevation.Since the spatial phase unwrapping is conducted based on the assumption of phase continuity,the inappropriate ambiguity will cause significant unwrapping errors.In this work,a 3D phase unwrapping algorithm assisted by image segmentation is proposed to address this issue.The Markov random field(MRF)is utilized for image segmentation.The optimal spatial phase unwrapping network is achieved based on the segmentation results.The asymptotic 3D phase unwrapping is adopted to get the refined 3D reconstruction.Results based on the real airborne array-InSAR data show that the proposed method effectively improves the elevation ambiguity.
基金supported by the National Natural Science Foundation of China (Grant Nos.62127802,61935005,and 61836002)。
文摘This year,the global data traffic will grow up to 4.8 zettabytes annually,which is 11 times more than all data traffic generated in 2012 (437 exabytes)[1].The huge data traffic is mainly caused by video-intensive services,such as Internetof-Things (IoT),4 K/8 K videos.The high capacity and bandwidth requirement from the transport network to the core is a major challenge in the 5G network.Therefore,the millimeter wave (MMW) with a much wider bandwidth is a very important backhaul solution [2,3].
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.62101133,62271279,62271282)the Natural Science Foundation of Shanghai(Grant No.21ZR1406800)the Shanghai Rising Star Program(Grant No.22QC1400100).
文摘Due to limited antenna space,high communication requirements,and strict regulatory constraints,the design of antennas for modern mobile phones has become an exceedingly challenging task.In recent years,numerous studies have been conducted in this area,leading to significant advancements.This review paper comprehensively summarizes recent progress made in antenna design for modern mobile phones.Firstly,the challenges faced in antenna design for modern mobile phones are described,including bandwidth enhancement,integration and decoupling techniques,mm-wave array antennas,satellite communication antennas,as well as interactions between mobile antennas and the human body.Secondly,the basic antenna types(such as inverted-F,slot,loop,and planar inverted-F antennas)commonly used in modern metal-bezel mobile phones along with their key characteristics are briefly summarized.Thirdly,the commonly exployed methods used in practical applications for designing wideband antennas within compact sizes and achieving decoupling among multiple antennas with wide bandwidths are collected.Fourthly,recent advances in the design of compact,wideband,and wide-angle scanning mm-wave arrays for modern mobile phones are summarized.Fifthly,recent progress made in satellite communication antenna designs for modern mobile phones,including broadside and end-fire radiation patterns,is presented.Sixthly,recent studies on the interaction between mobile antennas and the human body are briefly concluded.Finally,the future challenge of antenna design for mobile phones is briefly discussed.It is our hope that this comprehensive review will provide readers with a systematic understanding of antenna design principles applicable to modern mobile phones.
基金supported by the National Key Research and Development Program of China (No.2022YFB2802803)the National Natural Science Foundation of China (Nos.61925104,62031011,and 62201157)。
文摘This Letter proposes a post-equalizer for underwater visible light communication(UVLC) systems that combines channel estimation and joint time-frequency analysis, named channel-estimation-based bandpass variable-order time-frequency network(CBV-TFNet). By utilizing a bandpass variable-order loss function with communication prior knowledge, CBVTFNet enhances communication performance and training stability. It enables lightweight implementation and faster convergence through a channel estimation-based mask. The superior performance of the proposed equalization method over Volterra and deep neural network(DNN)-based methods has been studied experimentally. Using bit-power loading discrete multitone (DMT) modulation, the proposed method achieves a transmission bitrate of 4.956 Gbps through a 1.2 m underwater channel utilizing only 38.15% of real multiplication calculations compared to the DNN equalizer and achieving a bitrate gain of440 Mbps and a significantly larger dynamic range over the LMS-Volterra equalizer. Results highlight CBV-TFNet's potential for future post-equalization in UVLC systems.
基金supported by the National Key Research and Development Program of China (No.2022YFB2804502)the National Natural Science Foundation of China (No.62175143)。
文摘This paper reports a photonics-assisted millimeter-wave (mm-wave) joint radar jamming and secure communication system constructed through a photonic upconversion technique. In the experiments, a 30 GHz constant envelope linear frequency-modulated orthogonal frequency division modulation(CE-LFM-OFDM) signal with an instantaneous bandwidth of 1 GHz is synthesized by encoding 1 GBaud encrypted 16-quadrature amplitude modulation(16-QAM) OFDM signal. The velocity deception jamming is achieved with a spurious suppression ratio over 30 dB. Furthermore, we efficiently execute range deception jamming with a time shift of 10 ns. Simultaneously, the encrypted 16-QAM OFDM signal is successfully transmitted over a 1.2 m wireless link, with a data rate of 4 Gbit/s.
基金supported by the National Natural Science Foundation of China(No.62275052,No.62275148)Shanghai 2021 Science and Technology International Cooperation Project“Program of Action for Science and Technology Innovation”(21530710400)+1 种基金the Jiangsu Province's Industry Outlook and Key Core Technologies-Key Projects(BE2022055-4)the Open Fund of Laboratory of Science and Technology on Marine Navigation and Control,China State Shipbuilding Corporation(2023010102).
文摘Miniaturized fiber-optic magnetic field sensors have attracted considerable interest owing to their superiorities in anti-electromagnetic interference and compactness.However,the intrinsic thermodynamic properties of the material make temperature cross-sensitivity a challenging problem in terms of sensing accuracy and reliability.In this study,an ultracompact multicore fiber(MCF)tip sensor was designed to discriminatively measure the magnetic field and temperature,which was subsequently evaluated experimentally.The novel 3D printed sensing component consists of a bowl-shaped microcantilever and a polymer microfluid-infiltrated microcavity on the end-facet of an MCF,acting as two miniaturized Fabry-Perot interferometers.The magnetic sensitivity of the microcantilever was implemented by incorporating an iron micro ball into the microcantilever,and the microfluid-infiltrated microcavity enhanced the capability of highly sensitive temperature sensing.Using this tiny fiber-facet device in the two channels of an MCF allows discriminative measurements of the magnetic field and temperature by determining the sensitivity coefficient matrix of two parameters.The device exhibited a high magnetic field intensity sensitivity,approximately 1805.6 pm/mT with a fast response time of~213 ms and a high temperature sensitivity of 160.3 pm/℃.Moreover,the sensor had a low condition number of 11.28,indicating high reliability in two-parameter measurements.The proposed 3D printed MCF-tip probes,which detect multiple signals through multiple channels within a single fiber,can provide an ultracompact,sensitive,and reliable scheme for discriminative measurements.The bowl-shaped microcantilever also provides a useful platform for incorporating microstructures with functional materials,extending multi-parameter sensing scenarios and promoting the application of MCFs.
基金National Natural Science Foundation of China(NSFC)(61571133)National"863"Program of China(2015AA016904)
文摘Light-emitting diode(LED)-based visible light communication(VLC) has become a potential candidate for nextgeneration ultra-high-speed indoor wireless communication. In this paper, four special-shaped 8-quadrature amplitude modulation(QAM) constellations are investigated in a single-carrier VLC system. It is numerically verified and experimentally demonstrated that circular(7,1) shows obvious superiority in the performance of the dynamic range of signal voltage peak-to-peak(vpp) value and bit error rate(BER). Next best is rectangular, followed by triangular; circular(4,4) has the worst performance. A data rate of 1.515 Gbit/s is successfully achieved by circular(7,1) employing a red chip LED over 0.5 m indoor free space transmission below a BER threshold of3.8 × 10^(-3). Compared with circular(4,4), the traditional 8-QAM constellation, circular(7,1) provides a wider dynamic range of signal vpp, a higher data rate, and a longer transmission distance. To the best of our knowledge,this is the first investigation into the performance differences of special-shaped 8-QAM constellations in a highspeed, single-carrier VLC system, and the results comprehensively demonstrate that circular(7,1) is the optimal option.
基金the NNSF of China(No.61177071)the Key Program of Shanghai Science and Technology Association(12dz1143000)the NHTRDP(863 Program)of China(2013AA013603).
文摘Asymmetrically clipped optical orthogonal frequency division multiplexing(ACO-OFDM)has been a promising candidate in visible light communications(VLC)due to its improvement in power efficiency and reduction of nonlinearity based on previous simulation analysis.In this paper,for the first time as far as we know,we experimentally verify that ACO-OFDM would be an efficient scheme to improve the performance of a gigabit wavelength division multiplexing VLC system.Our theoretical investigations reveal that the advantages of ACO-OFDM can be attributed to the reduction of inter-carrier interference caused by signal–signal beating noise.An aggregate data rate of 1.05 Gb∕s is successfully achieved over 30 cm transmission below the 7%forwarderror-correction threshold of 3.8×10−3.The experimental results show that ACO-OFDM can outperform DC-biased optical OFDM by BER performance of 1.5 dB at the same data rate and 4 dB at the same bandwidth,which clearly demonstrates the benefit and feasibility of ACO-OFDM.
基金This work is supported by the National Natural Science Foundation of China under Grants No.11374063,11674062 and 11404348the National Key R&D Program of China(2017YFA0303403)+2 种基金the Shanghai Municipal Natural Science Foundation under Grant No.19ZR1402900the Natural Science Foundation of Jiangsu Province under grant No.BK20180456Fudan University-CIOMP Joint Fund(FC2019-006).
文摘The interactions between electrons and phonons play the key role in determining the carrier transport properties in semiconductors.In this work,comprehensive investigations on full electron–phonon(el–ph)couplings and their influences on carrier mobility and thermoelectric(TE)performances of 2D group IV and V elemental monolayers are performed,and we also analyze the selection rules on el–ph couplings using group theory.For shallow n/p-dopings in Si,Ge,and Sn,ZA/TA/LO phonon modes dominate the intervalley scatterings.Similarly strong intervalley scatterings via ZA/TO phonon modes can be identified for CBM electrons in P,As,and Sb,and for VBM holes,ZA/TA phonon modes dominate intervalley scatterings in P while LA phonons dominate intravalley scatterings in As and Sb.By considering full el–ph couplings,the TE performance for these two series of monolayers are predicted,which seriously downgrades the thermoelectric figures of merits compared with those predicted by the constant relaxation time approximation.
基金supported by the Chinese National Key R&D Projects(Grant No.2023YFB2905600)the National Natural Science Foundation of China(Grant Nos.62101121,62101126,62271135,62201393,and62201397)。
文摘Wavelength division multiplexing(WDM)and space division multiplexing(SDM)based on few-mode fiber(FMF)and multi-core fiber(MCF)have been vigorously developed to increase the transmission capacity of optical communication networks[1–5].However,the mode crosstalk generated in the mode division multiplexing(MDM)system causes the correlation between different mode signals,which seriously damages the transmission performance.Therefore,an effective multiple-input-multiple-output(MIMO)time domain or frequency domain equalizer should be used to eliminate the crosstalk between different mode signals.
