A mathematical simulating model of phased-array antenna in multifunction array radar has been approached in this paper, including the mathematical simulating model of plane phased-array pattern, the mathematical simul...A mathematical simulating model of phased-array antenna in multifunction array radar has been approached in this paper, including the mathematical simulating model of plane phased-array pattern, the mathematical simulating model of directionality factor, the mathematical simulating model of array factor, the mathematical simulating model of array element factor and the mathematical simulating model of beam steering.展开更多
Non-orthogonal multiple access(NOMA)is a promising technology for the next generation wireless communication networks.The benefits of this technology can be further enhanced through deployment in conjunction with mult...Non-orthogonal multiple access(NOMA)is a promising technology for the next generation wireless communication networks.The benefits of this technology can be further enhanced through deployment in conjunction with multiple-input multipleoutput(MIMO)systems.Antenna selection plays a critical role in MIMO–NOMA systems as it has the potential to significantly reduce the cost and complexity associated with radio frequency chains.This paper considers antenna selection for downlink MIMO–NOMA networks with multiple-antenna basestation(BS)and multiple-antenna user equipments(UEs).An iterative antenna selection scheme is developed for a two-user system,and to determine the initial power required for this selection scheme,a power estimation method is also proposed.The proposed algorithm is then extended to a general multiuser NOMA system.Numerical results demonstrate that the proposed antenna selection algorithm achieves near-optimal performance with much lower computational complexity in both two-user and multiuser scenarios.展开更多
Radio antenna arrays have many advantages for astronomical observations,such as high resolution,high sensitivity,multi-target simultaneous observation,and flexible beam formation.Problems surrounding key indices,such ...Radio antenna arrays have many advantages for astronomical observations,such as high resolution,high sensitivity,multi-target simultaneous observation,and flexible beam formation.Problems surrounding key indices,such as sensitivity enhancement,scanning range extension,and sidelobe level suppression,need to be solved urgently.Here,we propose a sparse optimization scheme based on a genetic algorithm for a 64-array element planar radio antenna array.As optimization targets for the iterative process of the genetic algorithm,we use the maximum sidelobe levels and beamwidth of multiple cross-section patterns that pass through the main beam in three-dimensions,with the maximum sidelobe levels of the patterns at several different scanning angles.Element positions are adjusted for iterations,to select the optimal array configuration.Following sparse layout optimization,the simulated 64-element planar radio antenna array shows that the maximum sidelobe level decreases by 1.79 dB,and the beamwidth narrows by 3°.Within the scan range of±30°,after sparse array optimization,all sidelobe levels decrease,and all beamwidths narrow.This performance improvement can potentially enhance the sensitivity and spatial resolution of radio telescope systems.展开更多
In this paper,we investigate covert communications under multi-antenna detection,and explore the impacts of the warden’s channel state information(CSI)availability and the noise uncertainty on system covert capabilit...In this paper,we investigate covert communications under multi-antenna detection,and explore the impacts of the warden’s channel state information(CSI)availability and the noise uncertainty on system covert capability.The detection performance at warden is analyzed in two cases under the perfect and statistical CSI at warden,respectively.In particular,for the former one,the warden utilizes the likelihood ratio(LR)detector,while for the latter one,the generalized likelihood ratio(GLR)detector is adopted.We first consider the scenario where the blocklength is finite,and demonstrate that the covert rate under both cases asymptotically goes to zero as the blocklength goes to infinity.Subsequently,we take the noise uncertainty at the warden into account which leads to positive covert rate,and characterize the covert rate for infinite blocklength.Specially,we derive the optimal transmit power for the legitimate transmitter that maximizes the covert rate.Besides,the rate gap under two cases,with different CSI availability at the warden,can be presented in closed form.Finally,numerical results validate the effectiveness of our theoretical analysis and also demonstrate the impacts of the factors studied on the system covertness.展开更多
In this paper,a dual-polarized antenna operating at 3.5 GHz is presented with 2D beam-scanning performance.The steerable beam is realized based on a 2×2 active reflective metasurface.The active metasurface is com...In this paper,a dual-polarized antenna operating at 3.5 GHz is presented with 2D beam-scanning performance.The steerable beam is realized based on a 2×2 active reflective metasurface.The active metasurface is composed of folded annular rings and cross dipoles embedded with voltage-controlled varactor diodes.By tuning the capacitance values of the varactors,the reflective phase of the metasurface is reconfigured to tilt the main beam.To verify the scanning performance,a prototype is fabricated and measured.At 3.5 GHz,the measured scanning ranges are from-25°to 29°and-27°to 29°in the XOZ and YOZ planes,respectively.展开更多
In this paper,a feature selection method for determining input parameters in antenna modeling is proposed.In antenna modeling,the input feature of artificial neural network(ANN)is geometric parameters.The selection cr...In this paper,a feature selection method for determining input parameters in antenna modeling is proposed.In antenna modeling,the input feature of artificial neural network(ANN)is geometric parameters.The selection criteria contain correlation and sensitivity between the geometric parameter and the electromagnetic(EM)response.Maximal information coefficient(MIC),an exploratory data mining tool,is introduced to evaluate both linear and nonlinear correlations.The EM response range is utilized to evaluate the sensitivity.The wide response range corresponding to varying values of a parameter implies the parameter is highly sensitive and the narrow response range suggests the parameter is insensitive.Only the parameter which is highly correlative and sensitive is selected as the input of ANN,and the sampling space of the model is highly reduced.The modeling of a wideband and circularly polarized antenna is studied as an example to verify the effectiveness of the proposed method.The number of input parameters decreases from8 to 4.The testing errors of|S_(11)|and axis ratio are reduced by8.74%and 8.95%,respectively,compared with the ANN with no feature selection.展开更多
A compact high-scanning-rate circular-polarized leaky-wave antenna(LWA)based on a meandering substrate integrated waveguide(SIW)with defected ground structures(DGSs)is presented.The meandering-SIW design is employed t...A compact high-scanning-rate circular-polarized leaky-wave antenna(LWA)based on a meandering substrate integrated waveguide(SIW)with defected ground structures(DGSs)is presented.The meandering-SIW design is employed to enhance the beam scanning rate,while circular polarization is achieved by etchingπ-shaped slots on the top plane.To suppress the open stopband at broadside,offset circular DGSs are periodically etched on the ground plane.Their impact on the reflection coefficient and axial ratio is then analyzed through a parametric study.A prototype of the antenna is simulated,fabricated,and measured.Both simulated and measured results indicate a scanning rate of approximately 8.6,with continuous beam scanning from-41°to 59°across the 11.3-12.7 GHz operating band.The antenna maintains an axial ratio below 3 dB within the 11.5-12.3 GHz range.This design shows promise for use in wireless communication systems,particularly in environments with increasingly limited spectrum resources.展开更多
The electromagnetic wave propagations and their coupling characteristics in magnetized plasma near the antenna of ion cyclotron range of frequencies(ICRF)is studied based on self-developed 3DFEM-IA code.This code effe...The electromagnetic wave propagations and their coupling characteristics in magnetized plasma near the antenna of ion cyclotron range of frequencies(ICRF)is studied based on self-developed 3DFEM-IA code.This code effectively resolves the three-dimensional(3D)geometry and the electromagnetic field using the finite element method.Our findings reveal that the distributions of electromagnetic fields and energy flow density significantly depend on the antenna phases,surface current density on the antenna straps,and background plasma density.Notably,the non-uniform surface current density on the antenna straps,resulting from the presence of induced currents,contributes to a reduction in coupling power within the edge plasma.Furthermore,the calculated coupling impedance increases with plasma density,corroborating well with experimental measurements.展开更多
A programmable low-profile array antenna based on nematic liquid crystals(NLCs)is proposed.Each antenna unit comprises a square patch radiating structure and a tunable NLC-based phase shifter capable of achieving a ph...A programmable low-profile array antenna based on nematic liquid crystals(NLCs)is proposed.Each antenna unit comprises a square patch radiating structure and a tunable NLC-based phase shifter capable of achieving a phase shift exceeding 360°with high linearity.First,the above 64 antenna units are periodically arranged into an 8×8 NLC-based antenna array,and the bias voltage of the NLC-based phase shifter loaded on the antenna unit is adjusted through the control of the field-programmable gate array(FPGA)programming sequences.This configuration enables precise phase changes for all 64 channels.Numerical simulation,sample processing,and experimental measurements of the antenna array are conducted to validate the performance of the antenna.The numerical and experimental results demonstrate that the proposed antenna performs well within the frequency range of 19.5-20.5 GHz,with a 3 dB relative bandwidth of 10%and a maximum main lobe gain of 14.1 dBi.A maximum scanning angle of±34°is achieved through the adjustment of the FPGA programming sequence.This NLC-based programmable array antenna shows promising potential for applications in satellite communication.展开更多
In mobile satellite communication networks employing digital beam forming technology,beam alignment imposes great influence on link quality and network efficiency.Owing to complex coupling motion by low earth orbit(LE...In mobile satellite communication networks employing digital beam forming technology,beam alignment imposes great influence on link quality and network efficiency.Owing to complex coupling motion by low earth orbit(LEO)satellite and ship,direction of arrival(DOA)of target satellite varies rapidly and nonlinearly.It then causes difficulty to accurately track the DOA.In this work,an adaptive tracking algorithm is proposed by exploiting advantages of flexible parameter configuration of digital phased-array antenna.The alignment process basically consists of observation and tracking.In the observation stage,two-dimensional(2-D)multiple signal classification(MUSIC)is applied by the ship-borne digital phased-array antenna to estimate beam direction of satellite;in the tracking stage,an extended Kalman filter(EKF)based adaptive tracking is designed to achieve fast and accurate alignment.The proposed adaptive tracking improves performance by adaptively estimating tracking parameters in EKF firstly.The estimation results are then used as feedback to adaptively adjust digital phased-array antenna parameters to improve estimation accuracy of DOA.Simulation results under sea state 5 show that the proposed tracking algorithm improves tracking accuracy and stability over conventional ones.展开更多
Planar phased-array satellite antennas deform when subjected to external disturbances such as thermal gradients or slewing maneuvers.Such distortion can degrade the coherence of the antenna and must therefore be elimi...Planar phased-array satellite antennas deform when subjected to external disturbances such as thermal gradients or slewing maneuvers.Such distortion can degrade the coherence of the antenna and must therefore be eliminated to maintain performance.To support planar phased-array satellite antennas,a truss with diagonal cables is often applied,generally pretensioned to improve the stiffness of the antenna and maintain the integrity of the structure.A new technique is proposed herein,using the diagonal cables as the actuators for static shape adjustment of the planar phased-array satellite antenna.In this technique,the diagonal cables are not pretensioned;instead,they are slack when the deformation of the antenna is small.When using this technique,there is no need to add redundant control devices,improving the reliability and reducing the mass of the antenna.The finite element method is used to establish a structural model for the satellite antenna,then a method is introduced to select proper diagonal cables and determine the corresponding forces.Numerical simulations of a simplified two-bay satellite antenna are first carried out to validate the proposed technique.Then,a simplified 18-bay antenna is also studied,because spaceborne satellite antennas have inevitably tended to be large in recent years.The numerical simulation results show that the proposed technique can be effectively used to adjust the static shape of planar phased-array satellite antennas,achieving high precision.展开更多
Design of multiple-feed lens antennas requires multivariate and multi-objective optimization processes,which can be accelerated by PSO algorithms.However,the PSO algorithm often fails to achieve optimal results with l...Design of multiple-feed lens antennas requires multivariate and multi-objective optimization processes,which can be accelerated by PSO algorithms.However,the PSO algorithm often fails to achieve optimal results with limited computation resources since spaces of candidate solutions are quite large for lens antenna designs.This paper presents a design paradigm for multiple-feed lens antennas based on a physics-assisted particle swarm optimization(PA-PSO)algorithm,which guides the swarm of particles based on laws of physics.As a proof of concept,a design of compact metalens antenna is proposed,which measures unprecedented performances,such as a field of view at±55°,a 21.7 dBi gain with a flatness within 4 dB,a 3-dB bandwidth>12°,and a compact design with a f-number of 0.2.The proposed PA-PSO algorithm reaches the optimal results 6 times faster than the ordinary PSO algorithm,which endows promising applications in the multivariate and multi-objective optimization processes,including but not limited to metalens antenna designs.展开更多
The Tianma 65 m radio telescope(TMRT)at Shanghai is a fully steerable single-dish radio telescope in China,operating at centimeter to millimeter wavelengths(1.25 GHz to 50 GHz).This paper presents details on the main ...The Tianma 65 m radio telescope(TMRT)at Shanghai is a fully steerable single-dish radio telescope in China,operating at centimeter to millimeter wavelengths(1.25 GHz to 50 GHz).This paper presents details on the main specifications,design,performance analysis,testing,and construction of the telescope antenna.The measured total efficiency is better than 50%over the whole elevation angle range,first sidelobe levels are less than−20 dB,antenna system noise temperatures are less than 70 K at 30°elevation angle,and pointing accuracy is less than 3″.The measured and calculated results are in good agreement,verifying the effectiveness of the design and analysis.展开更多
Efforts to protect electric power systems from faults have commonly relied on the use of ultra-high frequency(UHF)antennas for detecting partial discharge(PD)as a common precursor to faults.However,the effectiveness o...Efforts to protect electric power systems from faults have commonly relied on the use of ultra-high frequency(UHF)antennas for detecting partial discharge(PD)as a common precursor to faults.However,the effectiveness of existing UHF antennas suffers from a number of challenges such as limited bandwidth,relatively large physical size,and low detection sensitivity.The present study addresses these issues by proposing a compact microstrip patch antenna with fixed dimensions of 100 mm×100 mm×1.6 mm.The results of computations yield an optimized antenna design consisting of 2nd-order Hilbert fractal units positioned within a four-layer serpentine arrangement with a fractal unit connection distance of 3.0 mm.Specifically,the optimized antenna design achieves a detection bandwidth for which the voltage standing wave ratio is less than 2 that is approximately 97.3%of the UHF frequency range(0.3–3 GHz).Finally,a prototype antenna is fabricated using standard printed circuit board technology,and the results of experiments demonstrate that the proposed antenna is capable of detecting PD signals at a distance of 8 m from the discharge source.展开更多
This article presents an 8-element dual-polarized phased-array transceiver(TRX)front-end IC for millimeter-wave(mm-Wave)5G new radio(NR).Power enhancement technologies for power amplifiers(PA)in mm-Wave 5G phased-arra...This article presents an 8-element dual-polarized phased-array transceiver(TRX)front-end IC for millimeter-wave(mm-Wave)5G new radio(NR).Power enhancement technologies for power amplifiers(PA)in mm-Wave 5G phased-array TRX are discussed.A four-stage wideband high-power class-AB PA with distributed-active-transformer(DAT)power combining and multi-stage second-harmonic traps is proposed,ensuring the mitigated amplitude-to-phase(AM-PM)distortions across wide carrier frequencies without degrading transmitting(TX)power,gain and efficiency.TX and receiving(RX)switching is achieved by a matching network co-designed on-chip T/R switch.In each TRX element,6-bit 360°phase shifting and 6-bit 31.5-dB gain tuning are respectively achieved by the digital-controlled vector-modulated phase shifter(VMPS)and differential attenuator(ATT).Fabricated in 65-nm bulk complementary metal oxide semiconductor(CMOS),the proposed TRX demonstrates the measured peak TX/RX gains of 25.5/21.3 dB,covering the 24−29.5 GHz band.The measured peak TX OP1dB and power-added efficiency(PAE)are 20.8 dBm and 21.1%,respectively.The measured minimum RX NF is 4.1 dB.The TRX achieves an output power of 11.0−12.4 dBm and error vector magnitude(EVM)of 5%with 400-MHz 5G NR FR2 OFDM 64-QAM signals across 24−29.5 GHz,covering 3GPP 5G NR FR2 operating bands of n257,n258,and n261.展开更多
Two new ICRF antennas operating in the ion cyclotron radio frequency(ICRF) range have been developed for EAST to overcome the low coupling problem of the original antennas.The original ICRF antennas were limited in th...Two new ICRF antennas operating in the ion cyclotron radio frequency(ICRF) range have been developed for EAST to overcome the low coupling problem of the original antennas.The original ICRF antennas were limited in their power capacity due to insufficient coupling.The new antenna design takes into account both wave coupling and absorption processes through comprehensive wave coupling and absorption codes,with the dominant parallel wave number k∥of 7.5 m-1at dipole phasing.Through the use of these new ICRF antennas,we are able to achieve 3.8 MW output power and 360 s operation,respectively.The initial experimental results demonstrate the reliability of the antenna design method.展开更多
Low-cost GNSS receivers have recently been gaining reliability as good candidates for ionospheric studies. In line with these gains are genuine concerns about improving the performance of these receivers. In this work...Low-cost GNSS receivers have recently been gaining reliability as good candidates for ionospheric studies. In line with these gains are genuine concerns about improving the performance of these receivers. In this work, we present a comprehensive investigation of the performances of two antennas(the u-blox ANN-MB and the TOPGNSS TOP-106) used on a low-cost GNSS receiver known as the u-blox ZED-F9P. The two antennas were installed on two identical and co-located u-blox receivers. Data used from both receivers cover the period from January to June 2022. Results from the study indicate that the signal strengths are dominantly greater for the receiver with the TOPGNSS antenna than for the receiver with the ANN-MB antenna, implying that the TOPGNSS antenna is better than the ANN-MB antenna in terms of providing greater signal strengths. Summarily, the TOPGNSS antenna also performed better in minimizing the occurrence of cycle slips on phase TEC measurements. There are no conspicuous differences between the variances(computed as 5-min standard deviations) of phase TEC measurements for the two antennas, except for a period around May-June when the TOPGNSS gave a better performance in terms of minimizing the variances in phase TEC. Remarkably, the ANN-MB antenna gave a better performance than the TOPGNSS antenna in terms of minimizing the variances in pseudorange TEC for some satellite observations. For precise horizontal(North and East) positioning, the receiver with the TOPGNSS antenna gave better results, while the receiver with the ANN-MB antenna gave better vertical(Up) positioning. The errors for the receivers of both antennas are typically within about 5 m(the monthly mean was usually smaller than 1 m) in the horizontal direction and within about 10 m(the monthly mean was usually smaller than 4 m) in the vertical direction.展开更多
The use of metamaterial enhances the performance of a specific class of antennas known as metamaterial antennas.The radiation cost and quality factor of the antenna are influenced by the size of the antenna.Metamateri...The use of metamaterial enhances the performance of a specific class of antennas known as metamaterial antennas.The radiation cost and quality factor of the antenna are influenced by the size of the antenna.Metamaterial antennas allow for the circumvention of the bandwidth restriction for small antennas.Antenna parameters have recently been predicted using machine learning algorithms in existing literature.Machine learning can take the place of the manual process of experimenting to find the ideal simulated antenna parameters.The accuracy of the prediction will be primarily dependent on the model that is used.In this paper,a novel method for forecasting the bandwidth of the metamaterial antenna is proposed,based on using the Pearson Kernel as a standard kernel.Along with these new approaches,this paper suggests a unique hypersphere-based normalization to normalize the values of the dataset attributes and a dimensionality reduction method based on the Pearson kernel to reduce the dimension.A novel algorithm for optimizing the parameters of Convolutional Neural Network(CNN)based on improved Bat Algorithm-based Optimization with Pearson Mutation(BAO-PM)is also presented in this work.The prediction results of the proposed work are better when compared to the existing models in the literature.展开更多
In this paper,a dual-band graphene-based frequency selective surface(GFSS)is investigated and the operating mechanism of this GFSS is analyzed.By adjusting the bias voltage to control the graphene chemical po-tential ...In this paper,a dual-band graphene-based frequency selective surface(GFSS)is investigated and the operating mechanism of this GFSS is analyzed.By adjusting the bias voltage to control the graphene chemical po-tential between 0 eV and 0.5 eV,the GFSS can achieve four working states:dual-band passband,high-pass lowimpedance,low-pass high-impedance,and band-stop.Based on this GFSS,a hexagonal radome on a broadband omnidirectional monopole antenna is proposed,which can achieve independent 360°six-beam omnidirectional scanning at 1.08 THz and 1.58 THz dual bands.In addition,while increasing the directionality,the peak gains of the dual bands reach 7.44 dBi and 6.67 dBi,respectively.This work provides a simple method for realizing multi-band terahertz multi-beam reconfigurable antennas.展开更多
A novel metasurface antenna consisting of 5×5 rectangular patch elements is presented.Thestructure with and without the central element are both analyzed by the Characteristic Mode Theory(CMT).The developed mutua...A novel metasurface antenna consisting of 5×5 rectangular patch elements is presented.Thestructure with and without the central element are both analyzed by the Characteristic Mode Theory(CMT).The developed mutually orthogonal principal modes of the optimized periodic patch structure areexcited by a center-feed dipole.A differential feeding network is employed to realize impedance matching.Prototype with profile height of 0.07λ_(0)(λ_(0)is the wavelength in free space at the lowest operatingfrequency)is fabricated and assembled to verify the simulation results.The measured results show that thereflectance coefficient of proposed matesurface antenna is less than-10 dB in the whole operating bandrange from 4.2 GHz to 5.5 GHz,a relative bandwidth of 26.8%is achieved,and the maximummeasured realized gain is more than 9 dBi with a maximum radiation efficiency of 90%.The designprovides a guideline on the application of characteristic modes(CMs)to radiation problems.展开更多
文摘A mathematical simulating model of phased-array antenna in multifunction array radar has been approached in this paper, including the mathematical simulating model of plane phased-array pattern, the mathematical simulating model of directionality factor, the mathematical simulating model of array factor, the mathematical simulating model of array element factor and the mathematical simulating model of beam steering.
文摘Non-orthogonal multiple access(NOMA)is a promising technology for the next generation wireless communication networks.The benefits of this technology can be further enhanced through deployment in conjunction with multiple-input multipleoutput(MIMO)systems.Antenna selection plays a critical role in MIMO–NOMA systems as it has the potential to significantly reduce the cost and complexity associated with radio frequency chains.This paper considers antenna selection for downlink MIMO–NOMA networks with multiple-antenna basestation(BS)and multiple-antenna user equipments(UEs).An iterative antenna selection scheme is developed for a two-user system,and to determine the initial power required for this selection scheme,a power estimation method is also proposed.The proposed algorithm is then extended to a general multiuser NOMA system.Numerical results demonstrate that the proposed antenna selection algorithm achieves near-optimal performance with much lower computational complexity in both two-user and multiuser scenarios.
基金Ministry of Science and Technology SKA Special Project(2020SKA0110202)Special Project on Building a Science and Technology Innovation Center for South and Southeast Asia–International Joint Innovation Platform in Yunnan Province:"Yunnan Sino-Malaysian International Joint Laboratory of HF-VHF Advanced Radio Astronomy Technology"(202303AP140003)+4 种基金National Natural Science Foundation of China(NSFC)Joint Fund for Astronomy(JFA)incubator program(U2031133)International Partnership Program Project of the International Cooperation Bureau of the Chinese Academy of Sciences:"Belt and Road"Cooperation(114A11KYSB20200001)Kunming Foreign(International)Cooperation Base Program:"Yunnan Observatory of the Chinese Academy of Sciences-University of Malaya Joint R&D Cooperation Base for Advanced Radio Astronomy Technology"(GHJD-2021022)China-Malaysia Collaborative Research on Space Remote Sensing and Radio Astronomy Observation of Space Weather at Low and Middle Latitudes under the Key Special Project of the State Key R&D Program of the Ministry of Science and Technology for International Cooperation in Science,Technology and Innovation among Governments(2022YFE0140000)High-precision calibration method for low-frequency radio interferometric arrays for the SKA project of the Ministry of Science and Technology(2020SKA0110300).
文摘Radio antenna arrays have many advantages for astronomical observations,such as high resolution,high sensitivity,multi-target simultaneous observation,and flexible beam formation.Problems surrounding key indices,such as sensitivity enhancement,scanning range extension,and sidelobe level suppression,need to be solved urgently.Here,we propose a sparse optimization scheme based on a genetic algorithm for a 64-array element planar radio antenna array.As optimization targets for the iterative process of the genetic algorithm,we use the maximum sidelobe levels and beamwidth of multiple cross-section patterns that pass through the main beam in three-dimensions,with the maximum sidelobe levels of the patterns at several different scanning angles.Element positions are adjusted for iterations,to select the optimal array configuration.Following sparse layout optimization,the simulated 64-element planar radio antenna array shows that the maximum sidelobe level decreases by 1.79 dB,and the beamwidth narrows by 3°.Within the scan range of±30°,after sparse array optimization,all sidelobe levels decrease,and all beamwidths narrow.This performance improvement can potentially enhance the sensitivity and spatial resolution of radio telescope systems.
基金supported in part by the National Natural Science Foundation of China under Grants 62301117,62001094,and U19B2014in part by the National Key Laboratory of Wireless Communications Foundation under Grant 2023KP01602in part by the Natural Science Foundation of Xinjiang Uygur Autonomous Region under Grant 2022D01B184 and 2022D01A297.
文摘In this paper,we investigate covert communications under multi-antenna detection,and explore the impacts of the warden’s channel state information(CSI)availability and the noise uncertainty on system covert capability.The detection performance at warden is analyzed in two cases under the perfect and statistical CSI at warden,respectively.In particular,for the former one,the warden utilizes the likelihood ratio(LR)detector,while for the latter one,the generalized likelihood ratio(GLR)detector is adopted.We first consider the scenario where the blocklength is finite,and demonstrate that the covert rate under both cases asymptotically goes to zero as the blocklength goes to infinity.Subsequently,we take the noise uncertainty at the warden into account which leads to positive covert rate,and characterize the covert rate for infinite blocklength.Specially,we derive the optimal transmit power for the legitimate transmitter that maximizes the covert rate.Besides,the rate gap under two cases,with different CSI availability at the warden,can be presented in closed form.Finally,numerical results validate the effectiveness of our theoretical analysis and also demonstrate the impacts of the factors studied on the system covertness.
基金supported by ZTE Industry-University-Institute Cooperation Funds under Grant No.HC-CN-20220719005。
文摘In this paper,a dual-polarized antenna operating at 3.5 GHz is presented with 2D beam-scanning performance.The steerable beam is realized based on a 2×2 active reflective metasurface.The active metasurface is composed of folded annular rings and cross dipoles embedded with voltage-controlled varactor diodes.By tuning the capacitance values of the varactors,the reflective phase of the metasurface is reconfigured to tilt the main beam.To verify the scanning performance,a prototype is fabricated and measured.At 3.5 GHz,the measured scanning ranges are from-25°to 29°and-27°to 29°in the XOZ and YOZ planes,respectively.
基金National Natural Science Foundation of China(62161048)Sichuan Science and Technology Program(2022NSFSC0547,2022ZYD0109)。
文摘In this paper,a feature selection method for determining input parameters in antenna modeling is proposed.In antenna modeling,the input feature of artificial neural network(ANN)is geometric parameters.The selection criteria contain correlation and sensitivity between the geometric parameter and the electromagnetic(EM)response.Maximal information coefficient(MIC),an exploratory data mining tool,is introduced to evaluate both linear and nonlinear correlations.The EM response range is utilized to evaluate the sensitivity.The wide response range corresponding to varying values of a parameter implies the parameter is highly sensitive and the narrow response range suggests the parameter is insensitive.Only the parameter which is highly correlative and sensitive is selected as the input of ANN,and the sampling space of the model is highly reduced.The modeling of a wideband and circularly polarized antenna is studied as an example to verify the effectiveness of the proposed method.The number of input parameters decreases from8 to 4.The testing errors of|S_(11)|and axis ratio are reduced by8.74%and 8.95%,respectively,compared with the ANN with no feature selection.
文摘A compact high-scanning-rate circular-polarized leaky-wave antenna(LWA)based on a meandering substrate integrated waveguide(SIW)with defected ground structures(DGSs)is presented.The meandering-SIW design is employed to enhance the beam scanning rate,while circular polarization is achieved by etchingπ-shaped slots on the top plane.To suppress the open stopband at broadside,offset circular DGSs are periodically etched on the ground plane.Their impact on the reflection coefficient and axial ratio is then analyzed through a parametric study.A prototype of the antenna is simulated,fabricated,and measured.Both simulated and measured results indicate a scanning rate of approximately 8.6,with continuous beam scanning from-41°to 59°across the 11.3-12.7 GHz operating band.The antenna maintains an axial ratio below 3 dB within the 11.5-12.3 GHz range.This design shows promise for use in wireless communication systems,particularly in environments with increasingly limited spectrum resources.
基金Project supported by the National MCF Energy Research and Development Program(Grant No.2022YFE03190100)the National Natural Science Foundation of China(Grant Nos.12422513,12105035,and U21A20438)the Xiaomi Young Talents Program。
文摘The electromagnetic wave propagations and their coupling characteristics in magnetized plasma near the antenna of ion cyclotron range of frequencies(ICRF)is studied based on self-developed 3DFEM-IA code.This code effectively resolves the three-dimensional(3D)geometry and the electromagnetic field using the finite element method.Our findings reveal that the distributions of electromagnetic fields and energy flow density significantly depend on the antenna phases,surface current density on the antenna straps,and background plasma density.Notably,the non-uniform surface current density on the antenna straps,resulting from the presence of induced currents,contributes to a reduction in coupling power within the edge plasma.Furthermore,the calculated coupling impedance increases with plasma density,corroborating well with experimental measurements.
基金The National Natural Science Foundation of China(No.62401168,62401139,62401170)China Postdoctoral Science Foundation(No.2023MD744197)+2 种基金Postdoctoral Fellowship Program of CPSF(No.GZC20230631)Project for Enhancing Young and Middle-aged Teacher’s Research Basis Ability in Colleges of Guangxi(No.2023KY0218)Guangxi Key Laboratory Foundation of Optoelectronic Information Processing(No.GD23102)。
文摘A programmable low-profile array antenna based on nematic liquid crystals(NLCs)is proposed.Each antenna unit comprises a square patch radiating structure and a tunable NLC-based phase shifter capable of achieving a phase shift exceeding 360°with high linearity.First,the above 64 antenna units are periodically arranged into an 8×8 NLC-based antenna array,and the bias voltage of the NLC-based phase shifter loaded on the antenna unit is adjusted through the control of the field-programmable gate array(FPGA)programming sequences.This configuration enables precise phase changes for all 64 channels.Numerical simulation,sample processing,and experimental measurements of the antenna array are conducted to validate the performance of the antenna.The numerical and experimental results demonstrate that the proposed antenna performs well within the frequency range of 19.5-20.5 GHz,with a 3 dB relative bandwidth of 10%and a maximum main lobe gain of 14.1 dBi.A maximum scanning angle of±34°is achieved through the adjustment of the FPGA programming sequence.This NLC-based programmable array antenna shows promising potential for applications in satellite communication.
基金This work was supported by NSFC project(No.61971379)by Zhejiang Provincial NSFC project(No.LY16F010005).
文摘In mobile satellite communication networks employing digital beam forming technology,beam alignment imposes great influence on link quality and network efficiency.Owing to complex coupling motion by low earth orbit(LEO)satellite and ship,direction of arrival(DOA)of target satellite varies rapidly and nonlinearly.It then causes difficulty to accurately track the DOA.In this work,an adaptive tracking algorithm is proposed by exploiting advantages of flexible parameter configuration of digital phased-array antenna.The alignment process basically consists of observation and tracking.In the observation stage,two-dimensional(2-D)multiple signal classification(MUSIC)is applied by the ship-borne digital phased-array antenna to estimate beam direction of satellite;in the tracking stage,an extended Kalman filter(EKF)based adaptive tracking is designed to achieve fast and accurate alignment.The proposed adaptive tracking improves performance by adaptively estimating tracking parameters in EKF firstly.The estimation results are then used as feedback to adaptively adjust digital phased-array antenna parameters to improve estimation accuracy of DOA.Simulation results under sea state 5 show that the proposed tracking algorithm improves tracking accuracy and stability over conventional ones.
基金the National Natural Science Foundation of China(Grant 11772187)the research project of the Key Laboratory of Infrared System Detection and Imaging Technology of the Chinese Academy of Sciences(Grant CASIR201702)the Natural Science Foundation of Shanghai(Grant 16ZRi436200).
文摘Planar phased-array satellite antennas deform when subjected to external disturbances such as thermal gradients or slewing maneuvers.Such distortion can degrade the coherence of the antenna and must therefore be eliminated to maintain performance.To support planar phased-array satellite antennas,a truss with diagonal cables is often applied,generally pretensioned to improve the stiffness of the antenna and maintain the integrity of the structure.A new technique is proposed herein,using the diagonal cables as the actuators for static shape adjustment of the planar phased-array satellite antenna.In this technique,the diagonal cables are not pretensioned;instead,they are slack when the deformation of the antenna is small.When using this technique,there is no need to add redundant control devices,improving the reliability and reducing the mass of the antenna.The finite element method is used to establish a structural model for the satellite antenna,then a method is introduced to select proper diagonal cables and determine the corresponding forces.Numerical simulations of a simplified two-bay satellite antenna are first carried out to validate the proposed technique.Then,a simplified 18-bay antenna is also studied,because spaceborne satellite antennas have inevitably tended to be large in recent years.The numerical simulation results show that the proposed technique can be effectively used to adjust the static shape of planar phased-array satellite antennas,achieving high precision.
基金supported by the National Natural Science Foundation of China(61975026,62375232,6237523262205246 and 61875030)Creative Research Groups of the National Natural Science Foundation of Sichuan Province(2023NSFSC1973)+1 种基金the Shanghai Pilot Program for Basic Research,the National Key Research and Development Program of China(No.2023YFF0613600)Science and Technology Commission of Shanghai Municipality(No.22ZR1432400).
文摘Design of multiple-feed lens antennas requires multivariate and multi-objective optimization processes,which can be accelerated by PSO algorithms.However,the PSO algorithm often fails to achieve optimal results with limited computation resources since spaces of candidate solutions are quite large for lens antenna designs.This paper presents a design paradigm for multiple-feed lens antennas based on a physics-assisted particle swarm optimization(PA-PSO)algorithm,which guides the swarm of particles based on laws of physics.As a proof of concept,a design of compact metalens antenna is proposed,which measures unprecedented performances,such as a field of view at±55°,a 21.7 dBi gain with a flatness within 4 dB,a 3-dB bandwidth>12°,and a compact design with a f-number of 0.2.The proposed PA-PSO algorithm reaches the optimal results 6 times faster than the ordinary PSO algorithm,which endows promising applications in the multivariate and multi-objective optimization processes,including but not limited to metalens antenna designs.
文摘The Tianma 65 m radio telescope(TMRT)at Shanghai is a fully steerable single-dish radio telescope in China,operating at centimeter to millimeter wavelengths(1.25 GHz to 50 GHz).This paper presents details on the main specifications,design,performance analysis,testing,and construction of the telescope antenna.The measured total efficiency is better than 50%over the whole elevation angle range,first sidelobe levels are less than−20 dB,antenna system noise temperatures are less than 70 K at 30°elevation angle,and pointing accuracy is less than 3″.The measured and calculated results are in good agreement,verifying the effectiveness of the design and analysis.
文摘Efforts to protect electric power systems from faults have commonly relied on the use of ultra-high frequency(UHF)antennas for detecting partial discharge(PD)as a common precursor to faults.However,the effectiveness of existing UHF antennas suffers from a number of challenges such as limited bandwidth,relatively large physical size,and low detection sensitivity.The present study addresses these issues by proposing a compact microstrip patch antenna with fixed dimensions of 100 mm×100 mm×1.6 mm.The results of computations yield an optimized antenna design consisting of 2nd-order Hilbert fractal units positioned within a four-layer serpentine arrangement with a fractal unit connection distance of 3.0 mm.Specifically,the optimized antenna design achieves a detection bandwidth for which the voltage standing wave ratio is less than 2 that is approximately 97.3%of the UHF frequency range(0.3–3 GHz).Finally,a prototype antenna is fabricated using standard printed circuit board technology,and the results of experiments demonstrate that the proposed antenna is capable of detecting PD signals at a distance of 8 m from the discharge source.
基金This work was supported in part by the National Key Research and Development Program of China under Grant 2019YFB1803000in part by the Major Key Project of Peng Cheng Laboratory,Shenzhen,China,under Project PCL2021A01-2.
文摘This article presents an 8-element dual-polarized phased-array transceiver(TRX)front-end IC for millimeter-wave(mm-Wave)5G new radio(NR).Power enhancement technologies for power amplifiers(PA)in mm-Wave 5G phased-array TRX are discussed.A four-stage wideband high-power class-AB PA with distributed-active-transformer(DAT)power combining and multi-stage second-harmonic traps is proposed,ensuring the mitigated amplitude-to-phase(AM-PM)distortions across wide carrier frequencies without degrading transmitting(TX)power,gain and efficiency.TX and receiving(RX)switching is achieved by a matching network co-designed on-chip T/R switch.In each TRX element,6-bit 360°phase shifting and 6-bit 31.5-dB gain tuning are respectively achieved by the digital-controlled vector-modulated phase shifter(VMPS)and differential attenuator(ATT).Fabricated in 65-nm bulk complementary metal oxide semiconductor(CMOS),the proposed TRX demonstrates the measured peak TX/RX gains of 25.5/21.3 dB,covering the 24−29.5 GHz band.The measured peak TX OP1dB and power-added efficiency(PAE)are 20.8 dBm and 21.1%,respectively.The measured minimum RX NF is 4.1 dB.The TRX achieves an output power of 11.0−12.4 dBm and error vector magnitude(EVM)of 5%with 400-MHz 5G NR FR2 OFDM 64-QAM signals across 24−29.5 GHz,covering 3GPP 5G NR FR2 operating bands of n257,n258,and n261.
基金supported by the National Key Research and Development Program of China (Nos. 2019YFE03070000and 2019YFE03070003)National Natural Science Foundation of China (Nos. 11975265 and 11775258)+2 种基金Comprehensive Research Facility for Fusion Technology Program of China (No. 2018-000052-73-01-001228)the Open Fund of Magnetic Confinement Fusion Laboratory of Anhui Province (No. 2021AMF01001)Hefei Science Center,CAS(No. 2021HSC-KPRD001)。
文摘Two new ICRF antennas operating in the ion cyclotron radio frequency(ICRF) range have been developed for EAST to overcome the low coupling problem of the original antennas.The original ICRF antennas were limited in their power capacity due to insufficient coupling.The new antenna design takes into account both wave coupling and absorption processes through comprehensive wave coupling and absorption codes,with the dominant parallel wave number k∥of 7.5 m-1at dipole phasing.Through the use of these new ICRF antennas,we are able to achieve 3.8 MW output power and 360 s operation,respectively.The initial experimental results demonstrate the reliability of the antenna design method.
基金Centre for Atmospheric Research,Nigeria,for providing the research grant required to conduct this study。
文摘Low-cost GNSS receivers have recently been gaining reliability as good candidates for ionospheric studies. In line with these gains are genuine concerns about improving the performance of these receivers. In this work, we present a comprehensive investigation of the performances of two antennas(the u-blox ANN-MB and the TOPGNSS TOP-106) used on a low-cost GNSS receiver known as the u-blox ZED-F9P. The two antennas were installed on two identical and co-located u-blox receivers. Data used from both receivers cover the period from January to June 2022. Results from the study indicate that the signal strengths are dominantly greater for the receiver with the TOPGNSS antenna than for the receiver with the ANN-MB antenna, implying that the TOPGNSS antenna is better than the ANN-MB antenna in terms of providing greater signal strengths. Summarily, the TOPGNSS antenna also performed better in minimizing the occurrence of cycle slips on phase TEC measurements. There are no conspicuous differences between the variances(computed as 5-min standard deviations) of phase TEC measurements for the two antennas, except for a period around May-June when the TOPGNSS gave a better performance in terms of minimizing the variances in phase TEC. Remarkably, the ANN-MB antenna gave a better performance than the TOPGNSS antenna in terms of minimizing the variances in pseudorange TEC for some satellite observations. For precise horizontal(North and East) positioning, the receiver with the TOPGNSS antenna gave better results, while the receiver with the ANN-MB antenna gave better vertical(Up) positioning. The errors for the receivers of both antennas are typically within about 5 m(the monthly mean was usually smaller than 1 m) in the horizontal direction and within about 10 m(the monthly mean was usually smaller than 4 m) in the vertical direction.
文摘The use of metamaterial enhances the performance of a specific class of antennas known as metamaterial antennas.The radiation cost and quality factor of the antenna are influenced by the size of the antenna.Metamaterial antennas allow for the circumvention of the bandwidth restriction for small antennas.Antenna parameters have recently been predicted using machine learning algorithms in existing literature.Machine learning can take the place of the manual process of experimenting to find the ideal simulated antenna parameters.The accuracy of the prediction will be primarily dependent on the model that is used.In this paper,a novel method for forecasting the bandwidth of the metamaterial antenna is proposed,based on using the Pearson Kernel as a standard kernel.Along with these new approaches,this paper suggests a unique hypersphere-based normalization to normalize the values of the dataset attributes and a dimensionality reduction method based on the Pearson kernel to reduce the dimension.A novel algorithm for optimizing the parameters of Convolutional Neural Network(CNN)based on improved Bat Algorithm-based Optimization with Pearson Mutation(BAO-PM)is also presented in this work.The prediction results of the proposed work are better when compared to the existing models in the literature.
基金Supported by the Natural Science Foundation of Tibet Autonomous Region(XZ202401ZR0025)the National Natural Science Founda-tion of China(62164011,62301081)the Natural Science Foundation of Shaanxi Province(2022JQ-589)。
文摘In this paper,a dual-band graphene-based frequency selective surface(GFSS)is investigated and the operating mechanism of this GFSS is analyzed.By adjusting the bias voltage to control the graphene chemical po-tential between 0 eV and 0.5 eV,the GFSS can achieve four working states:dual-band passband,high-pass lowimpedance,low-pass high-impedance,and band-stop.Based on this GFSS,a hexagonal radome on a broadband omnidirectional monopole antenna is proposed,which can achieve independent 360°six-beam omnidirectional scanning at 1.08 THz and 1.58 THz dual bands.In addition,while increasing the directionality,the peak gains of the dual bands reach 7.44 dBi and 6.67 dBi,respectively.This work provides a simple method for realizing multi-band terahertz multi-beam reconfigurable antennas.
文摘A novel metasurface antenna consisting of 5×5 rectangular patch elements is presented.Thestructure with and without the central element are both analyzed by the Characteristic Mode Theory(CMT).The developed mutually orthogonal principal modes of the optimized periodic patch structure areexcited by a center-feed dipole.A differential feeding network is employed to realize impedance matching.Prototype with profile height of 0.07λ_(0)(λ_(0)is the wavelength in free space at the lowest operatingfrequency)is fabricated and assembled to verify the simulation results.The measured results show that thereflectance coefficient of proposed matesurface antenna is less than-10 dB in the whole operating bandrange from 4.2 GHz to 5.5 GHz,a relative bandwidth of 26.8%is achieved,and the maximummeasured realized gain is more than 9 dBi with a maximum radiation efficiency of 90%.The designprovides a guideline on the application of characteristic modes(CMs)to radiation problems.
