Metasurfaces,ultrathin two-dimensional version of metamaterials,have attracted tremendous attention due to their exotic capabilities to freely manipulate electromagnetic waves.By incorporating various tunable material...Metasurfaces,ultrathin two-dimensional version of metamaterials,have attracted tremendous attention due to their exotic capabilities to freely manipulate electromagnetic waves.By incorporating various tunable materials or elements into metasurface designs,reconfigurable metasurfaces and related metadevices with functionalities controlled by external stimuli can be realized,opening a new avenue to achieving dynamic manipulation of electromagnetic waves.Recently,based on the tunable metasurface concept,reconfigurable intelligent surfaces(RISs)have received significant attention and have been regarded as a promising emerging technology for future wireless communication due to their potential to enhance the capacity and coverage of wireless networks by smartly reconfiguring the wireless propagation environment.Here,in this article,we first focus on technical issues of RIS system implementation by reviewing the existing research contributions,paying special attention to designs in the microwave regime.Then,we showcase our recent attempts to practically demonstrate RIS systems in real-world applications,including deploying reflective RIS systems in indoor scenarios to enhance the wireless network coverage and utilizing intelligent omni-metasurfaces to improve both indoor and through-wall wireless communication quality.Finally,we give our own perspectives on possible future directions and existing challenges for RISs toward a truly commercial intelligent technology platform.展开更多
Electromagnetic(EM)metamaterials are artificially engineered materials with extraordinary EM properties beyond the limit of existing nat-ural materials;thus,they have been widely used to manipulate the amplitude,phase...Electromagnetic(EM)metamaterials are artificially engineered materials with extraordinary EM properties beyond the limit of existing nat-ural materials;thus,they have been widely used to manipulate the amplitude,phase,polarization,frequency,wave vector,waveform,and other degrees of freedom of EM waves in many practical applications.In this review,we will summarize recent advances in this flourishing field of EM metamateri-als,first from the perspectives of the classical regime and then the quantum regime.More specifically,in the classical regime,traditional EM metamate-rials are based on effective medium theory,and they have limitations of fixed functionalities and an inability to control EM waves in real time.To over-come these restrictions,information metamaterials,including digital coding and field-programmable metamaterials,have recently been proposed to en-able real-time manipulation of EM waves based on the theory of information science.By taking advantage of information metamaterials and artificial in-telligence,another crucial milestone of intelligent metamaterials has been achieved in the development of classical metamaterials.After overviewing EM metamaterials in the classical regime,we discuss cutting-edge studies of EM metamaterials in the quantum regime,namely,topological metamaterials and quantum metamaterials.These nonclassical metamaterials show excellent ability to flexibly manipulate the quantum states,and they extend the clas-sical information metamaterials into the field of quantum information science.At the end of this review,we will give some conclusions and perspectives on this fast-evolving field.展开更多
Microwave sensing offers important applications in areas such as data communication and remote sensing.It has thus received much attention from academia,industry,and governments.Atomic wireless sensing uses the strong...Microwave sensing offers important applications in areas such as data communication and remote sensing.It has thus received much attention from academia,industry,and governments.Atomic wireless sensing uses the strong response of the large electric dipole moment of a Rydberg atom in response to an external field to achieve precise measurement of a radio frequency(RF)signal.This method offers advantages over traditional wireless sensing including ultrawide energy level transitions,which makes it responsive to RF electric fields over a wide bandwidth.Here,we briefly review the progress of electric field measurement based on Rydberg atoms.We discuss the properties of Rydberg atoms,measurement using Rydberg atoms,experimental progress in electric field measurement of different bands,and different methods for detecting electric fields(such as atomic superheterodyne,machine learning,and critically enhanced measurement).The development of Rydberg atomic measurement focuses on the advantages of Rydberg atomic sensing,especially when compared to conventional microwave receivers.This work is of major significance to developing Rydberg-based measurements in astronomy,remote sensing,and other fields.展开更多
Searching for an optimal solution among many nonunique answers provided by transformation optics is critical for many branches of research,such as the burgeoning research on invisibility cloaks.The past decades have w...Searching for an optimal solution among many nonunique answers provided by transformation optics is critical for many branches of research,such as the burgeoning research on invisibility cloaks.The past decades have witnessed rapid development of transformation optics,and different kinds of invisibility cloaks have been designed and implemented.However,the available cloaks realized thus far have been mostly demonstrated with reduced parameters,which greatly impact the predefined cloaking performance.Here,we report a general design strategy to realize full-parameter omnidirectional cloaks that can hide arbitrarily shaped objects in free space.Our approach combines a singular transformation with transformation-invariant metamaterials.The cloaking device with extreme parameters is implemented using a metallic array structure.In the experiment,two cloak samples are designed and fabricated,one with nondiscrete cloaking regions and the other with separated hidden regions.Near-unit transmission of electromagnetic waves with arbitrary incident angles is experimentally demonstrated along with significantly suppressed scattering.Our work challenges the prevailing paradigms of invisibility cloaks and provides deep insight into how transformation optics could be harnessed to obtain easily-accessible metadevices.展开更多
The macroscopic electromagnetic properties of type-II superconductors are mainly influenced by the behavior of micro-scopic superconducting flux quantum units.Time-dependent Ginzburg-Landau(TDGL)theory is a well-known...The macroscopic electromagnetic properties of type-II superconductors are mainly influenced by the behavior of micro-scopic superconducting flux quantum units.Time-dependent Ginzburg-Landau(TDGL)theory is a well-known tool for describing and examining both the statics and dynamics of these superconducting entities.It have been instrumental in replicating and elucidat-ing numerous experimental results over the past decades.This paper provides a comprehensive overview of the progress in TDGL simulations,focusing on three key aspects of superconductor applications.We delve first into vortex rectification in supercon-ductors described within the TDGL framework,specifically highlighting the achievement of superconducting diode effect through asymmetric pinning landscapes and the reversible manipulation of vortex ratchets with dynamic pinning landscapes.In terms of the achievements of TDGL simulations concerning the critical current density of superconductors,we emphasize particularly on the optimization of pinning sites,including vortex pinning and dynamics in polycrystalline Nb3Sn with grain boundaries.In the third aspect,we concentrate on numerical modeling of vortex penetration and dynamics in superconducting radio-frequency cavities,including a discussion on superconductor-insulator-superconductor multilayer structures.Finally,we present key findings,insights,and perspectives derived from the discussed simulations.展开更多
Superconducting quantum interference devices(SQUIDs)are directly sensitive to magnetic flux.Nano-fabricated SQUID chip with miniaturized superconducting circuits can be further utilized as scanning probes for imaging ...Superconducting quantum interference devices(SQUIDs)are directly sensitive to magnetic flux.Nano-fabricated SQUID chip with miniaturized superconducting circuits can be further utilized as scanning probes for imaging of materials.Scanning SQUID microscopy(SSM)combines both high spatial resolution and high magnetic field sensitivity and is especially suitable for studying low dimensional materials with small sensing volumes.Here,we briefly review the fabrication of different types of nano-SQUIDs and the recent progress of utilizing them for scanning microscopy of quantum materials.We focus on but are not limited to topological states,unconventional superconductivity and exotic magnetism with a particular interest in two-dimensional materials.The magnet-ometry,susceptometry and current imaging modes of the SSM coupled with the external tuning of the material by magnetic field,electrical field gating and strain reveals a multitude of information beyond the scopes of charge-sensing probes.展开更多
The remarkable electromagnetic characteristics inherent in unconventional superconductors have catalyzed the advance-ment of numerous technological innovations,spanning from energy-efficient power transmission and hig...The remarkable electromagnetic characteristics inherent in unconventional superconductors have catalyzed the advance-ment of numerous technological innovations,spanning from energy-efficient power transmission and high-field magnets to sensitive detectors and quantum computing systems.Central to the functionality of these applications lies the superconducting characteristics,which govern pivotal phenomena including Cooper pair formation and macroscopic phase coherence,resulting in the attainment of zero electrical resistance,complete diamagnetism,and the Josephson tunneling effect.The complex phases and orders in these ma-terials significantly alter their key electronic and magnetic properties,posing challenges in elucidating the underlying physics and further enhancing their functional capabilities.The multiscale approach,representing a useful strategy for understanding materials across diverse length scales using a variety of experimental tools,can reveal intricate details in real and reciprocal spaces,facilitating cross-validation.In this brief review,we introduce the principle of the multiscale approach along with examples demonstrating its efficacy in unraveling the electronic and magnetic properties of unconventional superconductors.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
Radio frequency(RF)energy harvester as an efficient tool for capturing and converting the flourishing ambient RF energy provides a promising solution for long-term powering the wireless sensor networks and the Interne...Radio frequency(RF)energy harvester as an efficient tool for capturing and converting the flourishing ambient RF energy provides a promising solution for long-term powering the wireless sensor networks and the Internet of things(IoTs).However,the actual distribution of the environmental RF signals is dynamically frequency-dependent due to the diverse wireless terminals only interacting with specified frequencies.To take full advantage of the RF energy carrying this characteristic,an intelligent RF energy harvester is in demand to automatically sense the frequency information of an incident signal and conduct the corresponding RF-to-direct current transformation process.Here,to the best of my knowledge,a frequency-self-adaptive RF harvester is first presented with the help of the shape-reconfigurable liquid metal,which can precisely identify and efficiently convert an arbitrary signal from the frequency span of 1.8 to 2.6 GHz.Companied with a microcontroller unit and a tensile system,the dynamic functionality of the entire system is comprehensively demonstrated,showing promising potential to significantly advance various fields,including sustainable IoT applications,green wearable technologies,and self-powered devices.展开更多
Driven by the great demand for highly integrated wireless system-on-chip and system-in-package devices,there has recently been increas-ing interest in the research and development of differential antennas.Many studies...Driven by the great demand for highly integrated wireless system-on-chip and system-in-package devices,there has recently been increas-ing interest in the research and development of differential antennas.Many studies on the design,analysis,and measurement of differential antennas have been published.This paper presents an overview of the fundamentals and applications of differential antennas.First,it compares differential to bal-anced and single-ended to unbalanced antennas and explains why the new terms(differential and single-ended antennas)should be adopted instead of the old terms(balanced and unbalanced antennas).Second,it addresses the quantitative relationship between a differential antenna and its single-ended counterpart,which is important and useful because the properties of either the differential or single-ended antenna can be determined from the other with a known solution.Third,it describes how differential antennas can be measured,with a special emphasis on the balun method.Fourth,it classifies dif-ferential antennas into wire,slot,microstrip,printed,and dielectric resonator antennas to better present their suitability and functionality.Fifth,it pro-vides application examples of differential antennas from simple discrete wire to sophisticated microstrip designs.Finally,it is argued that the old paradigms of lower gains and bulkier sizes of differential antennas as compared to single-ended antennas do not always hold true;for instance,differen-tial microstrip patch antennas can possess comparable or even smaller sizes and higher gain values than single-ended microstrip patch antennas.展开更多
Time-modulated array(TMA)antennas,introduce the dimension of time into antenna design to control the radiation patterns and frequency spectral characteristics,thus improve the reconfigurability of array antennas and p...Time-modulated array(TMA)antennas,introduce the dimension of time into antenna design to control the radiation patterns and frequency spectral characteristics,thus improve the reconfigurability of array antennas and provide multiple functional-ities.They have great application potential in military and civilian fields,such as precision guidance and mobile communication,and are currently a hot spot of academic research.This article provides a review on the fundamentals and applications of TMAs.First,the basic theory and mathematical formulations of TMAs are introduced.Second,the most important applications of TMAs,namely time-modulated phased arrays(TMPA),are discussed from the perspectives of harmonic suppression and harmonic utiliza-tion,which are used for single-beam and multibeam radiation.Then,we survey the combination of TMA with various types of novel antenna arrays,such as single-channel digital beamforming(DBF)arrays,frequency diverse arrays(FDAs),and retrodirective arrays,to create new hardware implementation methods and enhance their performance.Next,recent advances in dedicated integrated chips for TMA,which have played a significant role in driving the progress of TMAs from academic research to practical applications,are presented.Finally,the challenges and prospects for TMAs are discussed,including new research directions and emerging applica-tion scenarios.展开更多
In this article,studies on the multimode excitation problem of waveguides and antennas,the balance/unbalance mech-anism and the balanced feeding techniques in dipole antenna systems are first briefly historically revi...In this article,studies on the multimode excitation problem of waveguides and antennas,the balance/unbalance mech-anism and the balanced feeding techniques in dipole antenna systems are first briefly historically reviewed.In this context,general-ized odd-even mode theory is advanced to quantitatively and approximately describe the mutual coupling effect between a feed line and an antenna.As is mathematically deduced and demonstrated,the modal parity mismatch between the feed line and the antenna should ultimately dominate the unbalance phenomenon in antenna systems.Thus,an elegant,closed-form formula is derived to ap-proximately calculate the“unbalance degree”of a straight dipole off-center fed by a symmetric twin-wire line.Design approaches for the simplest,linear,1-D multimode resonant antennas are introduced.Moreover,the“falling tone excitation”law gauged based on prototype dipoles is revealed and used to develop a mode synthesis design approach for microstrip patch antennas(MPAs)and 2-D sectorial electric dipole antennas.Design examples with distinctive radiation performance are presented and discussed.Finally,possible development trends of multimode resonant antennas are prospected.展开更多
A henge-like metaring(HMR)is proposed for improving the radiation pattern roundness of monopole antennas offcenter mounted on a finite ground by localizing the radiation from the monopole and suppressing the scatterin...A henge-like metaring(HMR)is proposed for improving the radiation pattern roundness of monopole antennas offcenter mounted on a finite ground by localizing the radiation from the monopole and suppressing the scattering by the ground.The improved patterns enhance uniform coverage of multiple-input and multiple-output(MIMO)systems.The study reveals that the radiation pattern of an off-center monopole is distorted by the asymmetric ground currents excited by both the feed and the radiation of the monopole.The distorted radiation patterns severely degrade wireless communication link quality.The HMR,composed of an annular array of mushroom unit cells,simultaneously functions as an electromagnetic bandgap(EBG)and a radiator,and encircles the monopole to form a henge monopole antenna(HMA).The HMR as an EBG is used to suppress the ground currents outside the HMR analyzed by an equivalent circuit model.The HMR as a radiator is designed to decouple the monopole from the ground with its elevated radiation pattern using characteristic mode analysis.As examples,two prototypes of single and four off-center MIMO HMAs are designed and investigated in the 2.45-GHz band.Simulated and measured results show that the single HMA and each of the four HMAs achieve the un-roundness of the radiation pattern atθ=65°plane lower than 2 dB and 3 dB in the 2.45-GHz band.As a result,near the radiation nulls,the SNR is improved by 6 dB.The compact construction and efficient current suppression facilitate the application of HMAs in multi-antenna systems above a finite ground with uniform coverage and reliable connections.展开更多
Metasurfaces,known as arrays of subwavelength antennas,provide a wide range of options for controlling electromagnetic waves and effectively reducing the size and complexity of electromagnetic devices.Metasurfaces can...Metasurfaces,known as arrays of subwavelength antennas,provide a wide range of options for controlling electromagnetic waves and effectively reducing the size and complexity of electromagnetic devices.Metasurfaces can manipulate five degrees of freedom of electromagnetic waves:amplitude,wavelength,polarization,phase,and orbital angular momentum;these are customized to provide a variety of remarkable functionalities,including metalenses and meta-holograms.With the advancement of simultaneously manipulating two or more degrees of freedom of the electromagnetic field,there has been a significant increase in the amount of information that electromagnetic waves can carry.The wavefront can be precisely tailored for specific applications,facilitating new possibilities for innovative applications with high performance and diverse functionalities,such as full-color vectorial meta-holograms achieved by a single-layer metasurface.This review briefly overviews the latest developments in metasurfaces,categorizing them based on their various degrees of freedom used to manipulate the electromagnetic waves.The use of metasurfaces to control electromagnetic waves from one dimension to multiple dimensions is systematically explored.The challenges and opportunities for future research are discussed.展开更多
Uniform circular arrays(UCAs)provide both omnidirectional(360°)and directive(sector)coverage of the azimuthal plane.Superdirective versions with unidirectional,high front-to-back ratio(FTBR)properties could provi...Uniform circular arrays(UCAs)provide both omnidirectional(360°)and directive(sector)coverage of the azimuthal plane.Superdirective versions with unidirectional,high front-to-back ratio(FTBR)properties could provide the radiated field char-acteristics being pursued for NextG wireless networks and their perceived applications.Typical UCA configurations–full,semi-circular,and sector–that radiate vertically-polarized(VP)fields and are composed of either omnidirectional electric dipole ele-ments or unidirectional Huygens dipole elements are analyzed first with conventional methods as reference cases.These omni-and uni-directional element configurations are then treated with several optimization techniques:the classic Rayleigh-quotient(RQ)method and its unidirectional-constrained version;the eigenbeam decomposition and synthesis(EBDS)technique used to design su-perdirective acoustic receiving arrays;and the Bessel-azimuthal multipole(BEAM)approach developed herein.Several arrays are identified as being superdirective with extremely high FTBR values.The performance characteristics of the arrays of unidirectional elements are demonstrated to be superior in general.Moreover,it is shown that larger radius arrays with RQ-specified excitation amplitudes are robust to changes in them whereas the outcomes of the corresponding small radius versions are not.On the other hand,the BEAM-optimized densely-packed small-radius superdirective arrays are quite tolerant to those variations while generating unidirectional pseudo-needle beams.展开更多
We propose and investigate a methodology based on convolved electric and magnetic currents for the generation of multi-band responses over a space-shared radiating surface.First,a single wideband antenna operation pri...We propose and investigate a methodology based on convolved electric and magnetic currents for the generation of multi-band responses over a space-shared radiating surface.First,a single wideband antenna operation principle based on inter-leaved dipole and slot modes is studied and analyzed using full-wave simulations followed by a qualitative time domain analysis.Subsequently,a 2×2 dual-band radiating unit is conceived and developed by closely arranging single wideband antennas.In this case,multimode resonances are generated in a lower frequency band by a proper convolving and coupling of the magnetic and electric currents realized in the gaps between the antennas and on the surface of the antennas,respectively.This methodology can be deployed repeatedly to build up a self-scalable topology by reusing the electromagnetically(EM)connected radiating surfaces and gaps be-tween the radiating units.Due to the efficient reuse of the electromagnetic region for the development of multiband radiation,a high aperture-reuse efficiency is achieved.Finally,as a proof of concept,a 2×4 dual-band array operating in Ku-and Ka-bands is devel-oped and fabricated by a linear arrangement of the two developed radiating units.Our measurement results show that the proposed antenna array provides impedance and gain bandwidths of 30%and 25.4%in the Ku-band and 10.65%and 8.52%in the Ka-band,respectively.展开更多
The rapid development of information technology leads a demand for high frequency soft magnetic materials with ex-ceptional radar wave absorption properties.A new magnetic material with superior radar wave absorption ...The rapid development of information technology leads a demand for high frequency soft magnetic materials with ex-ceptional radar wave absorption properties.A new magnetic material with superior radar wave absorption is explored in this paper.we explored the preparation of Y_(2)Co_(17)-xFex(x=0.0,1.0,2.0,3.0)alloy powders using yttrium oxide as a raw material by a low-cost and short preparation cycle reduction-diffusion process.The crystal structure,intrinsic magnetic properties,high frequency magnetism and radar wave absorption of Y_(2)Co_(17)-xFex(x=0.0,1.0,2.0,3.0)were investigated.These compounds have a perfect magnetic repair of Y_(2)Co_(17) and enable the improvement of the overall magnetic properties of Y_(2)Co_(17)-xFex(x=0.0,1.0,2.0,3.0)compounds.The Y_(2)Co_(17)-xFex/Polyurethane(PU)(x=0.0,1.0,2.0,3.0)absorbers were divided in detail using the zero-reflection mechanism.The results show that all Y_(2)Co_(17)-xFex/PU(x=0.0,1.0,2.0,3.0)absorbers have excellent absorption performance(reflection loss RL is less than-85 dB);in addition,Y_(2)Co_(15)Fe_(2)/PU absorbers and Y_(2)Co_(14)Fe_(3)/PU absorbers are superior candidates for S-band materials.In particular,the perfectly matched frequency fp of the modulated Y_(2)Co_(14)Fe_(3)/PU absorber is shifted to the L-band(1–2 GHz)where early warning radars are located.The Y_(2)Co_(14)Fe_(3)/PU absorber has an effective absorption bandwidth of 300 MHz(1.5–1.8 GHz)at a thickness of 5.230 mm.It can also absorb the full L-band at-4 dB,which has rarely been reported.展开更多
During the past several decades,the multimode resonator(MMR)technique has been extensively investigated and widely used,with successful exploration of a variety of high-performance patch antennas,slot antennas,dielect...During the past several decades,the multimode resonator(MMR)technique has been extensively investigated and widely used,with successful exploration of a variety of high-performance patch antennas,slot antennas,dielectric resonant antennas,dipole antennas,and so on.In this review paper,we summarize the research milestones for these MMR antennas worldwide as one of the most contributive research teams in this field.First,the basic working principles of the MMR technique are clearly illustrated and studied,including mode excitation,mode suppression,impedance performance improvement,and radiation performance improvement.Next,the research topics regarding impedance performance enhancement,i.e.,widebandwidth operation,multibandwidth operation,and mutual coupling reduction,based on the MMR method are intensively described.After that,the relevant works on radiation performance enhancement,i.e.,high-gain,wide-beamwidth,multibeam,multipolarization,low-cross-polarization,filtering-response,and leaky-wave antennas,based on the MMR method are extensively illustrated.By using this technique,several ideas about operating frequency reallocation,electric-field null control,radiation pattern reshaping,and efficiency null generation of the antennas are proposed and demonstrated by our team for the first time.In addition,the application of the MMR technique for wireless communication systems is introduced and presented,such as implant communication,wireless power transfer,and multiple-input multiple-output communication.With these arrangements,exploration and reporting of more interesting and useful MMR design methods can be anticipated in the future.展开更多
Maxwell’s equations for a mechano-driven media system(MEs-f-MDMS)have been used to characterize the electromagnetism of multislow-moving media that may be accelerated with complex trajectories.Such an approach starts...Maxwell’s equations for a mechano-driven media system(MEs-f-MDMS)have been used to characterize the electromagnetism of multislow-moving media that may be accelerated with complex trajectories.Such an approach starts from the integral forms of the four physics laws and is different from the classical approach of using the Lorentz transformation for correlating the electromagnetic phenomena observed in two inertial reference frames with relative motion.The governing equations inside the moving object/medium are the MEs-f-MDMS,and those in vacuum are the classical Maxwell’s equations;the full solutions of both reconcile at the medium surface/interface and satisfy the boundary conditions.This paper reviews the background,physical principle,and mathematical derivations for formulating the MEs-f-MDMS.Strategies are also presented for mathematically solving the MEs-f-MDMS.The unique advances made by the MEs-f-MDMS have been systematically summarized,as are their potential applications in engineering.We found that the Lorentz transformation is perfect for treating the electromagnetic phenomena of moving point charges in vacuum;however,for moving objects,the covariance of Maxwell’s equations may not hold,and use of the MEs-f-MDMS may be required if the velocity is low.Finally,recent advances for treating the boundary conditions at the nanoscale without assuming an abrupt boundary are also reviewed.展开更多
A liquid-loaded frequency tunable cavity bandpass filter (BPF) is presented. A dielectric fluidic material, dimethyl silicone oil (DSO) withexcellent thermophysical characteristics (working temperature from −50 ℃ to ...A liquid-loaded frequency tunable cavity bandpass filter (BPF) is presented. A dielectric fluidic material, dimethyl silicone oil (DSO) withexcellent thermophysical characteristics (working temperature from −50 ℃ to 180 ℃) and extremely low loss tangent is employed as a dielectric loading.The frequency reconfigurability of the proposed design is realized by altering the liquid level inside the cavity resonator. The filter achieves a widefrequency tuning range as well as a high Q factor. Moreover, this design shows significantly improved environmental suitability in extreme temperaturecases, outperforming the existing microfluidic-based RF devices using water or liquid metals. A four-pole tunable cavity bandpass filter is designed andverified. A cross-coupling structure comprising a metal loop structure is used to introduce transmission zeros in the proposed filter, which enhances theskirt selectivity and out-of-band rejections. We demonstrate that the center frequency of the proposed BPF can be tuned from 4.92 GHz to 6.16 GHz,and the filter achieves a high Q factor between 521 and 1527. The measured results agree well with simulated results.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.62271243,62071215,91963128,and 61731010)the National Key Research and Development Program of China(Grant No.2017YFA0700201)the Joint Fund of Ministry of Education for Equipment Pre-research(Grant No.8091B032112).
文摘Metasurfaces,ultrathin two-dimensional version of metamaterials,have attracted tremendous attention due to their exotic capabilities to freely manipulate electromagnetic waves.By incorporating various tunable materials or elements into metasurface designs,reconfigurable metasurfaces and related metadevices with functionalities controlled by external stimuli can be realized,opening a new avenue to achieving dynamic manipulation of electromagnetic waves.Recently,based on the tunable metasurface concept,reconfigurable intelligent surfaces(RISs)have received significant attention and have been regarded as a promising emerging technology for future wireless communication due to their potential to enhance the capacity and coverage of wireless networks by smartly reconfiguring the wireless propagation environment.Here,in this article,we first focus on technical issues of RIS system implementation by reviewing the existing research contributions,paying special attention to designs in the microwave regime.Then,we showcase our recent attempts to practically demonstrate RIS systems in real-world applications,including deploying reflective RIS systems in indoor scenarios to enhance the wireless network coverage and utilizing intelligent omni-metasurfaces to improve both indoor and through-wall wireless communication quality.Finally,we give our own perspectives on possible future directions and existing challenges for RISs toward a truly commercial intelligent technology platform.
基金supported by the National Natural Science Foundation of China(Grant Nos.62201136,62175215,62101124,and 62288101)National Key Research and Development Program of China(Grant Nos.2017YFA0700201,2017YFA0700202,and 2017YFA0700203)+1 种基金the Natural Science Foundation of Jiangsu Province(Grant Nos.BK20210209,BK20212002,and BK20220808)111 Project(Grant No.111-2-05).
文摘Electromagnetic(EM)metamaterials are artificially engineered materials with extraordinary EM properties beyond the limit of existing nat-ural materials;thus,they have been widely used to manipulate the amplitude,phase,polarization,frequency,wave vector,waveform,and other degrees of freedom of EM waves in many practical applications.In this review,we will summarize recent advances in this flourishing field of EM metamateri-als,first from the perspectives of the classical regime and then the quantum regime.More specifically,in the classical regime,traditional EM metamate-rials are based on effective medium theory,and they have limitations of fixed functionalities and an inability to control EM waves in real time.To over-come these restrictions,information metamaterials,including digital coding and field-programmable metamaterials,have recently been proposed to en-able real-time manipulation of EM waves based on the theory of information science.By taking advantage of information metamaterials and artificial in-telligence,another crucial milestone of intelligent metamaterials has been achieved in the development of classical metamaterials.After overviewing EM metamaterials in the classical regime,we discuss cutting-edge studies of EM metamaterials in the quantum regime,namely,topological metamaterials and quantum metamaterials.These nonclassical metamaterials show excellent ability to flexibly manipulate the quantum states,and they extend the clas-sical information metamaterials into the field of quantum information science.At the end of this review,we will give some conclusions and perspectives on this fast-evolving field.
基金supported by the National Key R&D Program of China(Grant No.2022YFA140400)the National Natural Science Foundation of China(Grant Nos.U20A20218,61525504,and 61435011)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2018490).
文摘Microwave sensing offers important applications in areas such as data communication and remote sensing.It has thus received much attention from academia,industry,and governments.Atomic wireless sensing uses the strong response of the large electric dipole moment of a Rydberg atom in response to an external field to achieve precise measurement of a radio frequency(RF)signal.This method offers advantages over traditional wireless sensing including ultrawide energy level transitions,which makes it responsive to RF electric fields over a wide bandwidth.Here,we briefly review the progress of electric field measurement based on Rydberg atoms.We discuss the properties of Rydberg atoms,measurement using Rydberg atoms,experimental progress in electric field measurement of different bands,and different methods for detecting electric fields(such as atomic superheterodyne,machine learning,and critically enhanced measurement).The development of Rydberg atomic measurement focuses on the advantages of Rydberg atomic sensing,especially when compared to conventional microwave receivers.This work is of major significance to developing Rydberg-based measurements in astronomy,remote sensing,and other fields.
基金sponsored by the Key Research and Development Program of the Ministry of Science and Technology(Grants Nos.2022Y FA1404704,2022YFA1405200,and 2022YFA1404902)the National Natural Science Foundation of China(Grant No.61975176)+5 种基金the Key Research and Development Program of Zhejiang Province(Grant No.2022C01036)the Fundamental Research Funds for the Central Universitiesthe work at Nanyang Technological University was sponsored by Singapore Ministry of Education(Grant No.MOE2018-T2-2-189(S))A*Star AME IRG Grant(Grant No.A20E5c0095)Programmatic Funds(Grant No.A18A7b0058)National Research Foundation Singapore Competitive Research Program(Grant Nos.NRF-CRP22-2019-0006 and NRF-CRP23-2019-0007).
文摘Searching for an optimal solution among many nonunique answers provided by transformation optics is critical for many branches of research,such as the burgeoning research on invisibility cloaks.The past decades have witnessed rapid development of transformation optics,and different kinds of invisibility cloaks have been designed and implemented.However,the available cloaks realized thus far have been mostly demonstrated with reduced parameters,which greatly impact the predefined cloaking performance.Here,we report a general design strategy to realize full-parameter omnidirectional cloaks that can hide arbitrarily shaped objects in free space.Our approach combines a singular transformation with transformation-invariant metamaterials.The cloaking device with extreme parameters is implemented using a metallic array structure.In the experiment,two cloak samples are designed and fabricated,one with nondiscrete cloaking regions and the other with separated hidden regions.Near-unit transmission of electromagnetic waves with arbitrary incident angles is experimentally demonstrated along with significantly suppressed scattering.Our work challenges the prevailing paradigms of invisibility cloaks and provides deep insight into how transformation optics could be harnessed to obtain easily-accessible metadevices.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.12372210 and 11972298).
文摘The macroscopic electromagnetic properties of type-II superconductors are mainly influenced by the behavior of micro-scopic superconducting flux quantum units.Time-dependent Ginzburg-Landau(TDGL)theory is a well-known tool for describing and examining both the statics and dynamics of these superconducting entities.It have been instrumental in replicating and elucidat-ing numerous experimental results over the past decades.This paper provides a comprehensive overview of the progress in TDGL simulations,focusing on three key aspects of superconductor applications.We delve first into vortex rectification in supercon-ductors described within the TDGL framework,specifically highlighting the achievement of superconducting diode effect through asymmetric pinning landscapes and the reversible manipulation of vortex ratchets with dynamic pinning landscapes.In terms of the achievements of TDGL simulations concerning the critical current density of superconductors,we emphasize particularly on the optimization of pinning sites,including vortex pinning and dynamics in polycrystalline Nb3Sn with grain boundaries.In the third aspect,we concentrate on numerical modeling of vortex penetration and dynamics in superconducting radio-frequency cavities,including a discussion on superconductor-insulator-superconductor multilayer structures.Finally,we present key findings,insights,and perspectives derived from the discussed simulations.
基金Yihua Wang would like to acknowledge support by Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)the National Key R&D Program of China(Grant No.2021YFA1400100)+2 种基金the National Natural Science Foundation of China(Grant No.12150003)Hao Li thanks the National Natural Science Foundation of China(Grant No.62201556)the Shanghai Pujiang Program(Grant No.22PJ1415200)for financial support.
文摘Superconducting quantum interference devices(SQUIDs)are directly sensitive to magnetic flux.Nano-fabricated SQUID chip with miniaturized superconducting circuits can be further utilized as scanning probes for imaging of materials.Scanning SQUID microscopy(SSM)combines both high spatial resolution and high magnetic field sensitivity and is especially suitable for studying low dimensional materials with small sensing volumes.Here,we briefly review the fabrication of different types of nano-SQUIDs and the recent progress of utilizing them for scanning microscopy of quantum materials.We focus on but are not limited to topological states,unconventional superconductivity and exotic magnetism with a particular interest in two-dimensional materials.The magnet-ometry,susceptometry and current imaging modes of the SSM coupled with the external tuning of the material by magnetic field,electrical field gating and strain reveals a multitude of information beyond the scopes of charge-sensing probes.
基金This work was supported by the National Natural Science Foundation of China(Grant No.12274439)the CAS Project for Young Scientists in Basic Research(Grant No.2022YSBR-048)。
文摘The remarkable electromagnetic characteristics inherent in unconventional superconductors have catalyzed the advance-ment of numerous technological innovations,spanning from energy-efficient power transmission and high-field magnets to sensitive detectors and quantum computing systems.Central to the functionality of these applications lies the superconducting characteristics,which govern pivotal phenomena including Cooper pair formation and macroscopic phase coherence,resulting in the attainment of zero electrical resistance,complete diamagnetism,and the Josephson tunneling effect.The complex phases and orders in these ma-terials significantly alter their key electronic and magnetic properties,posing challenges in elucidating the underlying physics and further enhancing their functional capabilities.The multiscale approach,representing a useful strategy for understanding materials across diverse length scales using a variety of experimental tools,can reveal intricate details in real and reciprocal spaces,facilitating cross-validation.In this brief review,we introduce the principle of the multiscale approach along with examples demonstrating its efficacy in unraveling the electronic and magnetic properties of unconventional superconductors.
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This work was supported in part by the National Natural Science Foundation of China(Grant No.62101394)the National Science Fund for Distinguished Young Scholars(Grant No.62225108)+1 种基金the Foundation from Guangxi Key Laboratory of Optoelectronic Information Processing(Grant No.GD21203)the Beijing Nova Program(Grant No.2304842874).
文摘Radio frequency(RF)energy harvester as an efficient tool for capturing and converting the flourishing ambient RF energy provides a promising solution for long-term powering the wireless sensor networks and the Internet of things(IoTs).However,the actual distribution of the environmental RF signals is dynamically frequency-dependent due to the diverse wireless terminals only interacting with specified frequencies.To take full advantage of the RF energy carrying this characteristic,an intelligent RF energy harvester is in demand to automatically sense the frequency information of an incident signal and conduct the corresponding RF-to-direct current transformation process.Here,to the best of my knowledge,a frequency-self-adaptive RF harvester is first presented with the help of the shape-reconfigurable liquid metal,which can precisely identify and efficiently convert an arbitrary signal from the frequency span of 1.8 to 2.6 GHz.Companied with a microcontroller unit and a tensile system,the dynamic functionality of the entire system is comprehensively demonstrated,showing promising potential to significantly advance various fields,including sustainable IoT applications,green wearable technologies,and self-powered devices.
文摘Driven by the great demand for highly integrated wireless system-on-chip and system-in-package devices,there has recently been increas-ing interest in the research and development of differential antennas.Many studies on the design,analysis,and measurement of differential antennas have been published.This paper presents an overview of the fundamentals and applications of differential antennas.First,it compares differential to bal-anced and single-ended to unbalanced antennas and explains why the new terms(differential and single-ended antennas)should be adopted instead of the old terms(balanced and unbalanced antennas).Second,it addresses the quantitative relationship between a differential antenna and its single-ended counterpart,which is important and useful because the properties of either the differential or single-ended antenna can be determined from the other with a known solution.Third,it describes how differential antennas can be measured,with a special emphasis on the balun method.Fourth,it classifies dif-ferential antennas into wire,slot,microstrip,printed,and dielectric resonator antennas to better present their suitability and functionality.Fifth,it pro-vides application examples of differential antennas from simple discrete wire to sophisticated microstrip designs.Finally,it is argued that the old paradigms of lower gains and bulkier sizes of differential antennas as compared to single-ended antennas do not always hold true;for instance,differen-tial microstrip patch antennas can possess comparable or even smaller sizes and higher gain values than single-ended microstrip patch antennas.
基金supported by the National Natural Science Foundation of China(Grant Nos.62101258,62071235 and 62271260)the Jiangsu Province Science&Technology Department(Grant No.BE2021017).
文摘Time-modulated array(TMA)antennas,introduce the dimension of time into antenna design to control the radiation patterns and frequency spectral characteristics,thus improve the reconfigurability of array antennas and provide multiple functional-ities.They have great application potential in military and civilian fields,such as precision guidance and mobile communication,and are currently a hot spot of academic research.This article provides a review on the fundamentals and applications of TMAs.First,the basic theory and mathematical formulations of TMAs are introduced.Second,the most important applications of TMAs,namely time-modulated phased arrays(TMPA),are discussed from the perspectives of harmonic suppression and harmonic utiliza-tion,which are used for single-beam and multibeam radiation.Then,we survey the combination of TMA with various types of novel antenna arrays,such as single-channel digital beamforming(DBF)arrays,frequency diverse arrays(FDAs),and retrodirective arrays,to create new hardware implementation methods and enhance their performance.Next,recent advances in dedicated integrated chips for TMA,which have played a significant role in driving the progress of TMAs from academic research to practical applications,are presented.Finally,the challenges and prospects for TMAs are discussed,including new research directions and emerging applica-tion scenarios.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFE0205900)the Key Technologies R&D Program of Jiangsu(Prospective and Key Technologies for Industry)(Grant Nos.BE2022067 and BE2022067-2)。
文摘In this article,studies on the multimode excitation problem of waveguides and antennas,the balance/unbalance mech-anism and the balanced feeding techniques in dipole antenna systems are first briefly historically reviewed.In this context,general-ized odd-even mode theory is advanced to quantitatively and approximately describe the mutual coupling effect between a feed line and an antenna.As is mathematically deduced and demonstrated,the modal parity mismatch between the feed line and the antenna should ultimately dominate the unbalance phenomenon in antenna systems.Thus,an elegant,closed-form formula is derived to ap-proximately calculate the“unbalance degree”of a straight dipole off-center fed by a symmetric twin-wire line.Design approaches for the simplest,linear,1-D multimode resonant antennas are introduced.Moreover,the“falling tone excitation”law gauged based on prototype dipoles is revealed and used to develop a mode synthesis design approach for microstrip patch antennas(MPAs)and 2-D sectorial electric dipole antennas.Design examples with distinctive radiation performance are presented and discussed.Finally,possible development trends of multimode resonant antennas are prospected.
文摘A henge-like metaring(HMR)is proposed for improving the radiation pattern roundness of monopole antennas offcenter mounted on a finite ground by localizing the radiation from the monopole and suppressing the scattering by the ground.The improved patterns enhance uniform coverage of multiple-input and multiple-output(MIMO)systems.The study reveals that the radiation pattern of an off-center monopole is distorted by the asymmetric ground currents excited by both the feed and the radiation of the monopole.The distorted radiation patterns severely degrade wireless communication link quality.The HMR,composed of an annular array of mushroom unit cells,simultaneously functions as an electromagnetic bandgap(EBG)and a radiator,and encircles the monopole to form a henge monopole antenna(HMA).The HMR as an EBG is used to suppress the ground currents outside the HMR analyzed by an equivalent circuit model.The HMR as a radiator is designed to decouple the monopole from the ground with its elevated radiation pattern using characteristic mode analysis.As examples,two prototypes of single and four off-center MIMO HMAs are designed and investigated in the 2.45-GHz band.Simulated and measured results show that the single HMA and each of the four HMAs achieve the un-roundness of the radiation pattern atθ=65°plane lower than 2 dB and 3 dB in the 2.45-GHz band.As a result,near the radiation nulls,the SNR is improved by 6 dB.The compact construction and efficient current suppression facilitate the application of HMAs in multi-antenna systems above a finite ground with uniform coverage and reliable connections.
文摘Metasurfaces,known as arrays of subwavelength antennas,provide a wide range of options for controlling electromagnetic waves and effectively reducing the size and complexity of electromagnetic devices.Metasurfaces can manipulate five degrees of freedom of electromagnetic waves:amplitude,wavelength,polarization,phase,and orbital angular momentum;these are customized to provide a variety of remarkable functionalities,including metalenses and meta-holograms.With the advancement of simultaneously manipulating two or more degrees of freedom of the electromagnetic field,there has been a significant increase in the amount of information that electromagnetic waves can carry.The wavefront can be precisely tailored for specific applications,facilitating new possibilities for innovative applications with high performance and diverse functionalities,such as full-color vectorial meta-holograms achieved by a single-layer metasurface.This review briefly overviews the latest developments in metasurfaces,categorizing them based on their various degrees of freedom used to manipulate the electromagnetic waves.The use of metasurfaces to control electromagnetic waves from one dimension to multiple dimensions is systematically explored.The challenges and opportunities for future research are discussed.
文摘Uniform circular arrays(UCAs)provide both omnidirectional(360°)and directive(sector)coverage of the azimuthal plane.Superdirective versions with unidirectional,high front-to-back ratio(FTBR)properties could provide the radiated field char-acteristics being pursued for NextG wireless networks and their perceived applications.Typical UCA configurations–full,semi-circular,and sector–that radiate vertically-polarized(VP)fields and are composed of either omnidirectional electric dipole ele-ments or unidirectional Huygens dipole elements are analyzed first with conventional methods as reference cases.These omni-and uni-directional element configurations are then treated with several optimization techniques:the classic Rayleigh-quotient(RQ)method and its unidirectional-constrained version;the eigenbeam decomposition and synthesis(EBDS)technique used to design su-perdirective acoustic receiving arrays;and the Bessel-azimuthal multipole(BEAM)approach developed herein.Several arrays are identified as being superdirective with extremely high FTBR values.The performance characteristics of the arrays of unidirectional elements are demonstrated to be superior in general.Moreover,it is shown that larger radius arrays with RQ-specified excitation amplitudes are robust to changes in them whereas the outcomes of the corresponding small radius versions are not.On the other hand,the BEAM-optimized densely-packed small-radius superdirective arrays are quite tolerant to those variations while generating unidirectional pseudo-needle beams.
文摘We propose and investigate a methodology based on convolved electric and magnetic currents for the generation of multi-band responses over a space-shared radiating surface.First,a single wideband antenna operation principle based on inter-leaved dipole and slot modes is studied and analyzed using full-wave simulations followed by a qualitative time domain analysis.Subsequently,a 2×2 dual-band radiating unit is conceived and developed by closely arranging single wideband antennas.In this case,multimode resonances are generated in a lower frequency band by a proper convolving and coupling of the magnetic and electric currents realized in the gaps between the antennas and on the surface of the antennas,respectively.This methodology can be deployed repeatedly to build up a self-scalable topology by reusing the electromagnetically(EM)connected radiating surfaces and gaps be-tween the radiating units.Due to the efficient reuse of the electromagnetic region for the development of multiband radiation,a high aperture-reuse efficiency is achieved.Finally,as a proof of concept,a 2×4 dual-band array operating in Ku-and Ka-bands is devel-oped and fabricated by a linear arrangement of the two developed radiating units.Our measurement results show that the proposed antenna array provides impedance and gain bandwidths of 30%and 25.4%in the Ku-band and 10.65%and 8.52%in the Ka-band,respectively.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFB3501302)the National Natural Science Foundation of China(Grant No.51731001)the Fund from the State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization’s Key Research and Development Projects.
文摘The rapid development of information technology leads a demand for high frequency soft magnetic materials with ex-ceptional radar wave absorption properties.A new magnetic material with superior radar wave absorption is explored in this paper.we explored the preparation of Y_(2)Co_(17)-xFex(x=0.0,1.0,2.0,3.0)alloy powders using yttrium oxide as a raw material by a low-cost and short preparation cycle reduction-diffusion process.The crystal structure,intrinsic magnetic properties,high frequency magnetism and radar wave absorption of Y_(2)Co_(17)-xFex(x=0.0,1.0,2.0,3.0)were investigated.These compounds have a perfect magnetic repair of Y_(2)Co_(17) and enable the improvement of the overall magnetic properties of Y_(2)Co_(17)-xFex(x=0.0,1.0,2.0,3.0)compounds.The Y_(2)Co_(17)-xFex/Polyurethane(PU)(x=0.0,1.0,2.0,3.0)absorbers were divided in detail using the zero-reflection mechanism.The results show that all Y_(2)Co_(17)-xFex/PU(x=0.0,1.0,2.0,3.0)absorbers have excellent absorption performance(reflection loss RL is less than-85 dB);in addition,Y_(2)Co_(15)Fe_(2)/PU absorbers and Y_(2)Co_(14)Fe_(3)/PU absorbers are superior candidates for S-band materials.In particular,the perfectly matched frequency fp of the modulated Y_(2)Co_(14)Fe_(3)/PU absorber is shifted to the L-band(1–2 GHz)where early warning radars are located.The Y_(2)Co_(14)Fe_(3)/PU absorber has an effective absorption bandwidth of 300 MHz(1.5–1.8 GHz)at a thickness of 5.230 mm.It can also absorb the full L-band at-4 dB,which has rarely been reported.
基金supported by the National Natural Science Foundation of China(Grant Nos.61571468,61801348,61971475,and 62271364)the Key Research and Development Program of Shaanxi(Grant No.2023-GHZD-45).
文摘During the past several decades,the multimode resonator(MMR)technique has been extensively investigated and widely used,with successful exploration of a variety of high-performance patch antennas,slot antennas,dielectric resonant antennas,dipole antennas,and so on.In this review paper,we summarize the research milestones for these MMR antennas worldwide as one of the most contributive research teams in this field.First,the basic working principles of the MMR technique are clearly illustrated and studied,including mode excitation,mode suppression,impedance performance improvement,and radiation performance improvement.Next,the research topics regarding impedance performance enhancement,i.e.,widebandwidth operation,multibandwidth operation,and mutual coupling reduction,based on the MMR method are intensively described.After that,the relevant works on radiation performance enhancement,i.e.,high-gain,wide-beamwidth,multibeam,multipolarization,low-cross-polarization,filtering-response,and leaky-wave antennas,based on the MMR method are extensively illustrated.By using this technique,several ideas about operating frequency reallocation,electric-field null control,radiation pattern reshaping,and efficiency null generation of the antennas are proposed and demonstrated by our team for the first time.In addition,the application of the MMR technique for wireless communication systems is introduced and presented,such as implant communication,wireless power transfer,and multiple-input multiple-output communication.With these arrangements,exploration and reporting of more interesting and useful MMR design methods can be anticipated in the future.
文摘Maxwell’s equations for a mechano-driven media system(MEs-f-MDMS)have been used to characterize the electromagnetism of multislow-moving media that may be accelerated with complex trajectories.Such an approach starts from the integral forms of the four physics laws and is different from the classical approach of using the Lorentz transformation for correlating the electromagnetic phenomena observed in two inertial reference frames with relative motion.The governing equations inside the moving object/medium are the MEs-f-MDMS,and those in vacuum are the classical Maxwell’s equations;the full solutions of both reconcile at the medium surface/interface and satisfy the boundary conditions.This paper reviews the background,physical principle,and mathematical derivations for formulating the MEs-f-MDMS.Strategies are also presented for mathematically solving the MEs-f-MDMS.The unique advances made by the MEs-f-MDMS have been systematically summarized,as are their potential applications in engineering.We found that the Lorentz transformation is perfect for treating the electromagnetic phenomena of moving point charges in vacuum;however,for moving objects,the covariance of Maxwell’s equations may not hold,and use of the MEs-f-MDMS may be required if the velocity is low.Finally,recent advances for treating the boundary conditions at the nanoscale without assuming an abrupt boundary are also reviewed.
基金supported in part by the National Defense Basic Scientific Research Program of China(Grant No.JCKYS2021DC05)in part by The Fund of Prospective Layout of Scientific Research for Nanjing University of Aeronautics and Astronautics(NUAA)。
文摘A liquid-loaded frequency tunable cavity bandpass filter (BPF) is presented. A dielectric fluidic material, dimethyl silicone oil (DSO) withexcellent thermophysical characteristics (working temperature from −50 ℃ to 180 ℃) and extremely low loss tangent is employed as a dielectric loading.The frequency reconfigurability of the proposed design is realized by altering the liquid level inside the cavity resonator. The filter achieves a widefrequency tuning range as well as a high Q factor. Moreover, this design shows significantly improved environmental suitability in extreme temperaturecases, outperforming the existing microfluidic-based RF devices using water or liquid metals. A four-pole tunable cavity bandpass filter is designed andverified. A cross-coupling structure comprising a metal loop structure is used to introduce transmission zeros in the proposed filter, which enhances theskirt selectivity and out-of-band rejections. We demonstrate that the center frequency of the proposed BPF can be tuned from 4.92 GHz to 6.16 GHz,and the filter achieves a high Q factor between 521 and 1527. The measured results agree well with simulated results.
