The terahertz(THz)antennas,which have features of small size,wide frequency bandwidth and high data rate,are important devices for transmitting and receiving THz electromagnetic waves in the emerging THz systems.Howev...The terahertz(THz)antennas,which have features of small size,wide frequency bandwidth and high data rate,are important devices for transmitting and receiving THz electromagnetic waves in the emerging THz systems.However,most of THz antennas suffer from relatively high loss and low fabrication precision due to their small sizes in high frequency bands of THz waves.Therefore,this paper presents a detailed overview of the most recent research on the performance improvement of THz antennas.Firstly,the development of THz antennas is briefly reviewed and the basic design ideas of THz antennas are introduced.Then,THz antennas are categorized as metallic antennas,dielectric antennas and new material antennas.After that,the latest research progress in THz photoconductive antennas,THz horn antennas,THz lens antennas,THz microstrip antennas and THz on-chip antennas are discussed.In particular,the practical difficulties for the development of THz antennas are discussed with promising approaches.In addition,this paper also presents a short review of the process technology of THz antennas.Finally,the vital challenges and the future research directions for THz antennas are presented.展开更多
In this paper,a new compact ultrawideband(UWB)circularly polarized(CP)antenna array for vehicular communications is proposed.The antenna array consists of a 2×2 sequentially rotated T-shaped cross dipole,four par...In this paper,a new compact ultrawideband(UWB)circularly polarized(CP)antenna array for vehicular communications is proposed.The antenna array consists of a 2×2 sequentially rotated T-shaped cross dipole,four parasitic elements,and a feeding network.By loading the T-shaped cross dipoles with parasitic rectangular elements with cut corners,the bandwidth can be expanded.On this basis,the radiation pattern can be improved by the topology with sequential rotation of four T-shaped cross-dipole antennas,and the axial ratio(AR)bandwidth of the antenna also can be further enhanced.In addition,due to the special topology that the vertical arms of all Tshaped cross dipoles are all oriented toward the center of the antenna array,the gain of proposed antenna is improved while the size of the antenna is almost the same as the traditional cross dipole.Simulated and measured results show that the proposed antenna has good CP characteristics,an impedance bandwidth for S11<-10 d B of about 106.1%(3.26:1,1.57-5.12 GHz)and the 3-d B AR bandwidth of about 104.1%(3.17:1,1.57-4.98 GHz),a wide 3-d B gain bandwidth of 73.3%as well as the peak gain of 8.6 d Bic at 3.5 GHz.The overall size of antenna is 0.56λ×0.56λ×0.12λ(λrefers to the wavelength of the lowest operating frequency in free space).The good performance of this compact UWB CP antenna array is promising for applications in vehicular communications.展开更多
In the era of Internet of Things(Io T),mobile edge computing(MEC)and wireless power transfer(WPT)provide a prominent solution for computation-intensive applications to enhance computation capability and achieve sustai...In the era of Internet of Things(Io T),mobile edge computing(MEC)and wireless power transfer(WPT)provide a prominent solution for computation-intensive applications to enhance computation capability and achieve sustainable energy supply.A wireless-powered mobile edge computing(WPMEC)system consisting of a hybrid access point(HAP)combined with MEC servers and many users is considered in this paper.In particular,a novel multiuser cooperation scheme based on orthogonal frequency division multiple access(OFDMA)is provided to improve the computation performance,where users can split the computation tasks into various parts for local computing,offloading to corresponding helper,and HAP for remote execution respectively with the aid of helper.Specifically,we aim at maximizing the weighted sum computation rate(WSCR)by optimizing time assignment,computation-task allocation,and transmission power at the same time while keeping energy neutrality in mind.We transform the original non-convex optimization problem to a convex optimization problem and then obtain a semi-closed form expression of the optimal solution by considering the convex optimization techniques.Simulation results demonstrate that the proposed multi-user cooperationassisted WPMEC scheme greatly improves the WSCR of all users than the existing schemes.In addition,OFDMA protocol increases the fairness and decreases delay among the users when compared to TDMA protocol.展开更多
The high reliability of the communication system is critical in metro and mining applications for personal safety,channel optimization,and improving operational performance.This paper surveys the progress of wireless ...The high reliability of the communication system is critical in metro and mining applications for personal safety,channel optimization,and improving operational performance.This paper surveys the progress of wireless communication systems in underground environments such as tunnels and mines from 1920 to 2022,including the evolution of primitive technology,advancements in channel modelling,and realization of various wireless propagation channels.In addition,the existing and advanced channel modeling strategies,which include the evolution of different technologies and their applications;mathematical,analytical,and experimental techniques for radio propagation;and significance of the radiation characteristics,antenna placement,and physical environment of multiple-input multiple-output(MIMO)communication systems,are analyzed.The given study introduces leaky coaxial cable(LCX)and distributed antenna system(DAS)designs for improving narrowband and wideband channel capacity.The paper concludes by figuring out open research areas for the future technologies.展开更多
Metamaterial design,encompassing both microstructure topology selection and geometric parameter optimization,constitutes a high-dimensional optimization problem,with computationally expensive and time-consuming design...Metamaterial design,encompassing both microstructure topology selection and geometric parameter optimization,constitutes a high-dimensional optimization problem,with computationally expensive and time-consuming design evaluations.Bayesian optimization(BO)offers a promising approach for black-box optimization involved in various material designs,and this work presents several advanced techniques to adapt BO to address the challenges associated with metamaterial design.First,variational autoencoders(VAEs)are employed for efficient dimensionality reduction,mapping complex,high-dimensional metamaterial microstructures into a compact latent space.Second,mutual information maximization is incorporated into the VAE to enhance the quality of the learned latent space,ensuring that the most relevant features for optimization are retained.Third,trust region-based Bayesian optimization(TuRBO)dynamically adjusts local search regions,ensuring stability and convergence in high-dimensional spaces.The proposed techniques are well incorporated with conventional Gaussian processes(GP)-based BO framework.We applied the proposed method for the design of electromagnetic metamaterial microstructures.Experimental results show that we achieve a significantly high probability of finding the ground-truth topology types and their geometric parameters,leading to high accuracy in matching the design target.Moreover,our approach demonstrates significant time efficiency compared with traditional design methods.展开更多
In addition to offering morphological visualizations via capture of the spatial distributions of optical absorption,photoacoustic imaging technology can reveal abundant physical information about biological particles,...In addition to offering morphological visualizations via capture of the spatial distributions of optical absorption,photoacoustic imaging technology can reveal abundant physical information about biological particles,including their orientation,density,and viscoelasticity,through analysis of the pressure transients in the spectral domain.However,the low-amplitude wideband photoacoustic signals of intrinsic microscopic optically-absorbing objects under the action of confined photoacoustic excitation power continue to hinder simultaneous photoacoustic structural imaging and spectroscopic analysis of the nonfluorescent chromophores in living biological tissues because of the inadequate responses to photoacoustic impulses observed in most photoacoustic imaging setups that include piezoelectric transducers.Building upon a recently-developed optical evanescent wave sensor that can respond to ultrasound with high sensitivity over a broad frequency range,we propose in vivo spatial-spectral photoacoustic microscopy for recovery of structural imaging in three dimensions and characterization of anatomical features in the acoustic frequency domain.Label-free photoacoustic images of a living zebrafish are acquired in which spectroscopically-resolved differentiation of the microarchitecture is accessed,along with isometric micrometer-scale volumetric visualizations.The proposed imaging technology could potentially provide more comprehensive evaluations of the physiopathological status of living small animals.展开更多
As structured optical fields with spatially inhomogeneous polarization distributions,vector beams have attracted widespread attention for their great applications across multiple fields.The coupling between spatial mo...As structured optical fields with spatially inhomogeneous polarization distributions,vector beams have attracted widespread attention for their great applications across multiple fields.The coupling between spatial modes and polarization states in vector beams results in nonseparability analogous to quantum entangled states,referred to as classical entanglement.This concept has garnered considerable scholarly interest,due to its capacity to facilitate quantum-inspired approaches for the characterization of vector optical fields,leading to noteworthy applications such as metrological sensing,communication encryption,and quantum computing.However,most investigations concerning classical entanglement have focused on vector optical fields within the spatial domain,while the classical entanglement characteristics of ultrafast vector beam pulses in the temporal domain remain to be revealed.Here,we investigate the classical local entanglement of ultrafast vector beam pulses in the temporal domain.Through theoretical interpretation and experimental verification,time-varying nonseparability has been demonstrated throughout the pulse duration.The dynamic evolution of spatially vectorial polarization states on femtosecond timescales was measured.The temporal evolution of the classical entanglement and the associated density matrix were analyzed using quantum state tomography.This research provides,to our knowledge,novel perspectives for investigating quantum-classical optical analogies in the temporal domain,advancing deeper fundamental understanding of entanglement.展开更多
基金supported in part by the National Natural Science Foundation of China(NSFC)under Grants No.61801299 and No.61372077in part by the Shenzhen Science and Technology Program under Grants GJHZ 20180418190529516 and JSGG 20180507183215520。
文摘The terahertz(THz)antennas,which have features of small size,wide frequency bandwidth and high data rate,are important devices for transmitting and receiving THz electromagnetic waves in the emerging THz systems.However,most of THz antennas suffer from relatively high loss and low fabrication precision due to their small sizes in high frequency bands of THz waves.Therefore,this paper presents a detailed overview of the most recent research on the performance improvement of THz antennas.Firstly,the development of THz antennas is briefly reviewed and the basic design ideas of THz antennas are introduced.Then,THz antennas are categorized as metallic antennas,dielectric antennas and new material antennas.After that,the latest research progress in THz photoconductive antennas,THz horn antennas,THz lens antennas,THz microstrip antennas and THz on-chip antennas are discussed.In particular,the practical difficulties for the development of THz antennas are discussed with promising approaches.In addition,this paper also presents a short review of the process technology of THz antennas.Finally,the vital challenges and the future research directions for THz antennas are presented.
基金supported in part by the National Natural Science Foundation of China(NSFC)under Grant No.62071306in part by Shenzhen Science and Technology Program under Grants JCYJ202001091-13601723,JSGG20210802154203011 and JSGG-20210420091805014。
文摘In this paper,a new compact ultrawideband(UWB)circularly polarized(CP)antenna array for vehicular communications is proposed.The antenna array consists of a 2×2 sequentially rotated T-shaped cross dipole,four parasitic elements,and a feeding network.By loading the T-shaped cross dipoles with parasitic rectangular elements with cut corners,the bandwidth can be expanded.On this basis,the radiation pattern can be improved by the topology with sequential rotation of four T-shaped cross-dipole antennas,and the axial ratio(AR)bandwidth of the antenna also can be further enhanced.In addition,due to the special topology that the vertical arms of all Tshaped cross dipoles are all oriented toward the center of the antenna array,the gain of proposed antenna is improved while the size of the antenna is almost the same as the traditional cross dipole.Simulated and measured results show that the proposed antenna has good CP characteristics,an impedance bandwidth for S11<-10 d B of about 106.1%(3.26:1,1.57-5.12 GHz)and the 3-d B AR bandwidth of about 104.1%(3.17:1,1.57-4.98 GHz),a wide 3-d B gain bandwidth of 73.3%as well as the peak gain of 8.6 d Bic at 3.5 GHz.The overall size of antenna is 0.56λ×0.56λ×0.12λ(λrefers to the wavelength of the lowest operating frequency in free space).The good performance of this compact UWB CP antenna array is promising for applications in vehicular communications.
基金supported in part by the National Natural Science Foundation of China(NSFC)under Grant No.62071306in part by Shenzhen Science and Technology Program under Grants JCYJ20200109113601723,JSGG20210802154203011 and JSGG20210420091805014。
文摘In the era of Internet of Things(Io T),mobile edge computing(MEC)and wireless power transfer(WPT)provide a prominent solution for computation-intensive applications to enhance computation capability and achieve sustainable energy supply.A wireless-powered mobile edge computing(WPMEC)system consisting of a hybrid access point(HAP)combined with MEC servers and many users is considered in this paper.In particular,a novel multiuser cooperation scheme based on orthogonal frequency division multiple access(OFDMA)is provided to improve the computation performance,where users can split the computation tasks into various parts for local computing,offloading to corresponding helper,and HAP for remote execution respectively with the aid of helper.Specifically,we aim at maximizing the weighted sum computation rate(WSCR)by optimizing time assignment,computation-task allocation,and transmission power at the same time while keeping energy neutrality in mind.We transform the original non-convex optimization problem to a convex optimization problem and then obtain a semi-closed form expression of the optimal solution by considering the convex optimization techniques.Simulation results demonstrate that the proposed multi-user cooperationassisted WPMEC scheme greatly improves the WSCR of all users than the existing schemes.In addition,OFDMA protocol increases the fairness and decreases delay among the users when compared to TDMA protocol.
文摘The high reliability of the communication system is critical in metro and mining applications for personal safety,channel optimization,and improving operational performance.This paper surveys the progress of wireless communication systems in underground environments such as tunnels and mines from 1920 to 2022,including the evolution of primitive technology,advancements in channel modelling,and realization of various wireless propagation channels.In addition,the existing and advanced channel modeling strategies,which include the evolution of different technologies and their applications;mathematical,analytical,and experimental techniques for radio propagation;and significance of the radiation characteristics,antenna placement,and physical environment of multiple-input multiple-output(MIMO)communication systems,are analyzed.The given study introduces leaky coaxial cable(LCX)and distributed antenna system(DAS)designs for improving narrowband and wideband channel capacity.The paper concludes by figuring out open research areas for the future technologies.
基金supported by the National Key R&D Program of China No.2021YFB3802103Open Project of the State Key Laboratory of Metamaterial Electromagnetic Modulation Technology:“Research on Optimization Algorithms for Antenna Wideband Matching Network Parameters”.
文摘Metamaterial design,encompassing both microstructure topology selection and geometric parameter optimization,constitutes a high-dimensional optimization problem,with computationally expensive and time-consuming design evaluations.Bayesian optimization(BO)offers a promising approach for black-box optimization involved in various material designs,and this work presents several advanced techniques to adapt BO to address the challenges associated with metamaterial design.First,variational autoencoders(VAEs)are employed for efficient dimensionality reduction,mapping complex,high-dimensional metamaterial microstructures into a compact latent space.Second,mutual information maximization is incorporated into the VAE to enhance the quality of the learned latent space,ensuring that the most relevant features for optimization are retained.Third,trust region-based Bayesian optimization(TuRBO)dynamically adjusts local search regions,ensuring stability and convergence in high-dimensional spaces.The proposed techniques are well incorporated with conventional Gaussian processes(GP)-based BO framework.We applied the proposed method for the design of electromagnetic metamaterial microstructures.Experimental results show that we achieve a significantly high probability of finding the ground-truth topology types and their geometric parameters,leading to high accuracy in matching the design target.Moreover,our approach demonstrates significant time efficiency compared with traditional design methods.
基金This work was supported in part by the Guangdong Major Project of Basic and Applied Basic Research[grant number 2020B0301030009]the National Natural Science Foundation of China(NSFC)[grant numbers 62175159,62175157,12174204,62071306]+3 种基金the Natural Science Foundation of Guangdong Province,Guangdong,China[2023A1515012888]the Science and Technology Innovation Commission of Shenzhen[grant numbers KQTD20170330110444030,JCYJ20200109113808048,RCJC20210609103232046,JCYJ20200109113601723,JSGG20210802154203011,JSGG20210420091805014,JCYJ20220818101417039]Key Research Project of Zhejiang Lab:K2022MG0AC05China Postdoctoral Science Foundation:2022M722174.
文摘In addition to offering morphological visualizations via capture of the spatial distributions of optical absorption,photoacoustic imaging technology can reveal abundant physical information about biological particles,including their orientation,density,and viscoelasticity,through analysis of the pressure transients in the spectral domain.However,the low-amplitude wideband photoacoustic signals of intrinsic microscopic optically-absorbing objects under the action of confined photoacoustic excitation power continue to hinder simultaneous photoacoustic structural imaging and spectroscopic analysis of the nonfluorescent chromophores in living biological tissues because of the inadequate responses to photoacoustic impulses observed in most photoacoustic imaging setups that include piezoelectric transducers.Building upon a recently-developed optical evanescent wave sensor that can respond to ultrasound with high sensitivity over a broad frequency range,we propose in vivo spatial-spectral photoacoustic microscopy for recovery of structural imaging in three dimensions and characterization of anatomical features in the acoustic frequency domain.Label-free photoacoustic images of a living zebrafish are acquired in which spectroscopically-resolved differentiation of the microarchitecture is accessed,along with isometric micrometer-scale volumetric visualizations.The proposed imaging technology could potentially provide more comprehensive evaluations of the physiopathological status of living small animals.
基金Basic and Applied Basic Research Foundation of Guangdong Province(2020B0301030009)National Key Research and Development Program of China(2023YFE0107900)+2 种基金National Natural Science Foundation of China(62175157,62375177)Shenzhen Science and Technology Program(JCYJ20210324120403011,JCYJ20241202124219023,RCJC20210609103232046)Research Team Cultivation Program of Shenzhen University(2023QNT014)。
文摘As structured optical fields with spatially inhomogeneous polarization distributions,vector beams have attracted widespread attention for their great applications across multiple fields.The coupling between spatial modes and polarization states in vector beams results in nonseparability analogous to quantum entangled states,referred to as classical entanglement.This concept has garnered considerable scholarly interest,due to its capacity to facilitate quantum-inspired approaches for the characterization of vector optical fields,leading to noteworthy applications such as metrological sensing,communication encryption,and quantum computing.However,most investigations concerning classical entanglement have focused on vector optical fields within the spatial domain,while the classical entanglement characteristics of ultrafast vector beam pulses in the temporal domain remain to be revealed.Here,we investigate the classical local entanglement of ultrafast vector beam pulses in the temporal domain.Through theoretical interpretation and experimental verification,time-varying nonseparability has been demonstrated throughout the pulse duration.The dynamic evolution of spatially vectorial polarization states on femtosecond timescales was measured.The temporal evolution of the classical entanglement and the associated density matrix were analyzed using quantum state tomography.This research provides,to our knowledge,novel perspectives for investigating quantum-classical optical analogies in the temporal domain,advancing deeper fundamental understanding of entanglement.
