A multi-band metamaterial antenna is proposed to operate at the terahertz(THz)band for medical applications.The proposed structure is designed on a polyimide as a support layer,and its radiating elements are made of g...A multi-band metamaterial antenna is proposed to operate at the terahertz(THz)band for medical applications.The proposed structure is designed on a polyimide as a support layer,and its radiating elements are made of graphene.Initially,the design is started with a conventional shape showing a single operating frequency at 1.1 THz.To achieve a multi-band operating frequency,the conventional shape was replaced with the proposed metamaterial as a radiating patch that has properties not exist in nature.The multi-band frequencies are obtained without compromising the overall size of the design.The overall size is 600×600×25μm^(3).The operating frequencies are 0.36,0.49,0.69,0.87,and 1.04 THz.A full ground plane is used to behave as isolation between the design and the human body model.The proposed design is investigated on free space and on the human body model,showing excellent performance in both cases.The achieved gains for the following frequencies 0.36,0.49,0.69,0.87,and 1.04 THz are 4.81,6.5,8.41,6.02,and 7.96 dB,respectively,while the efficiencies are 83.91%,96.28%,90.80%,91.71%,and 92.99%,respectively.The conventional design was modified to have a partial ground to show the benefit of using the full ground.The design is loaded on the human body model and its performance is affected.The efficiency and gain are 6.61 dB and 95.58.7%for the case of no human body model,and 4.26 dB and 40.30%for the case of using a human body model.Hence,the proposed metamaterial antenna will be useful for future medical applications in the THz band.展开更多
A new multi-band and high-speed endoscope diagnostic for the observation of visible light has been successfully developed on the Experimental Advanced Superconducting Tokamak.The mirror with an aperture is designed at...A new multi-band and high-speed endoscope diagnostic for the observation of visible light has been successfully developed on the Experimental Advanced Superconducting Tokamak.The mirror with an aperture is designed at the head of the optical system.Based on two dichroic mirrors,the system is divided into three imaging mirror groups with different bands,i.e.B(380-500 nm),G(500-580 nm)and R(580-750 nm)bands,and its focal length is 16 mm with a relatively large aperture of D/f=1:4.The spatial resolution is less than 5 mm near the object distance of 1750 mm with the camera NAC ACS-1 M60.This optical system will be used to contrastively study both the spatial distribution and time evolution of different impurities in the same field of view.The experimental results confirm that it can be applied to the recognition of plasma boundary and related physical research.展开更多
The property of multi-band operation has been studied and investigated analytically through the design of a rectangular patch microstrip antenna having different numbers of wide slots arranged at both the radiating ed...The property of multi-band operation has been studied and investigated analytically through the design of a rectangular patch microstrip antenna having different numbers of wide slots arranged at both the radiating edges. The analyses were carried out using the method of moments simulation software. It is shown that a patch with three slots has a multi-band feature with four resonant frequencies at 1.6, 1.8, 2.65, and 4.83 GHz and adequate values of return loss and gain. It is also shown that a patch with two pairs of wide slots arranged at both the radiating edges has the dual band feature with resonant frequencies at 1.64 and 1.8 GHz and good values of return loss and gain.展开更多
Cognitive radio(CR) technology is considered to be an effective solution to allocate spectrum resources,whereas the primary users of a network do not fully utilize available frequency bands.Spectrum auction framewor...Cognitive radio(CR) technology is considered to be an effective solution to allocate spectrum resources,whereas the primary users of a network do not fully utilize available frequency bands.Spectrum auction framework has been recognized as an effective way to achieve dynamic spectrum access.From the perspective of spectrum auction,multi-band multi-user auction provides a new challenge for spectrum management.This paper proposes an auction framework based on location information for multi-band multi-user spectrum allocation.The performance of the proposed framework is compared with that of traditional auction framework based on a binary interference model as a benchmark.Simulation results show that primary users will obtain more total system revenue by selling their idle frequency bands to secondary users and the spectrum utilization of the proposed framework is more effective and fairer.展开更多
This analysis focuses on PIM interference under multi-band multi-signal input in mobile communication system.Unlike single band system that only odd order PIM(especially 3rd order) should be concerned,in multi-band mu...This analysis focuses on PIM interference under multi-band multi-signal input in mobile communication system.Unlike single band system that only odd order PIM(especially 3rd order) should be concerned,in multi-band multi-signal case,both odd and even order PIM could be interference source because of more complicated intermodulation,more IMPs generated and more receive bands.Especially,the 2nd order PIM may interfere more serious to receiving channel for its strong magnitude.In duplex indoor distribute system,the PIM interference is a potential problem to GSM900,DCS1800,CDMA,and even 3G system wireless services,because the PIM frequencies may fall in receive bands and interfere to the receiving channels.In radio system design and wireless channel assignment,precautions must be taken to minimize the PIM level and to avoid interfere to receiving channels.For practical use,the lower order possible PIM interference to 2G and 3G systems is calculated.展开更多
We present a high-efficiency tunable wide-angle multi-band reflective linear-to-linear(LTL)polarization converter,which is composed of an array of two L-shaped graphene patches with different sizes.In the mid-infrared...We present a high-efficiency tunable wide-angle multi-band reflective linear-to-linear(LTL)polarization converter,which is composed of an array of two L-shaped graphene patches with different sizes.In the mid-infrared region,the proposed converter can transform x-polarized wave into y-polarized wave at four resonant frequencies.The polarization conversion ratios of the four bands reach 94.4%,92.7%,99.3%,and 93.1%,respectively.By carefully choosing the geometric parameter,triple-band LTL polarization conversion can also be realized.The three polarization conversion ratios reach 91.50%,99.20%,and 97.22%,respectively.The influence of incident angle on the performances of the LTL polarization converter is investigated,and it is found that our polarization converter shows the angle insensitivity.Also,the dynamically tunable properties of the proposed polarization converter are numerically studied by changing Fermi energy.All the simulation results are conducted by finite element method.展开更多
In this paper, a multi-band metasurface(MS) antenna array with low radar cross section(RCS) performance is proposed and measured. Firstly, a 44 antenna array is composed of four 22 Jerusalem cross structure antenn...In this paper, a multi-band metasurface(MS) antenna array with low radar cross section(RCS) performance is proposed and measured. Firstly, a 44 antenna array is composed of four 22 Jerusalem cross structure antenna arrays working at different frequency bands, which is aimed at enhancing the bandwidth effectively. Then, each antenna can be seen as a unit of MS in spite of adding the feeding structure. Based on phase cancellation principle, the MS is arranged into a chessboard configuration in order to realize wideband RCS reduction. Thus, excellent radiation and scattering characteristics are obtained simultaneously. Simulated and measured results indicate that this work provides a novel method to achieve bandwidth expansion as well as wideband RCS reduction of the antenna array.展开更多
Traditional multi-band frequency selective surface (FSS) approaches are hard to achieve a perfect resonance response in a wide band due to the limit of the onset grating lobe frequency determined by the array. To so...Traditional multi-band frequency selective surface (FSS) approaches are hard to achieve a perfect resonance response in a wide band due to the limit of the onset grating lobe frequency determined by the array. To solve this problem, an approach of combining elements in different period to build a hybrid array is presented. The results of series of numerical simulation show that multi-periodicity combined element FSS, which are designed using this approach, usually have much weaker grating lobes than the traditional FSS. Furthermore, their frequency response can be well predicted through the properties of their member element FSS. A prediction method for estimating the degree of expected grating lobe energy loss in designing multi-band FSS using this approach is provided.展开更多
The influence of the gap on the absorption performance of the conventional split ring resonator(SRR) absorber is investigated at microwave frequencies. Our simulated results reveal that the geometry of the square SRR ...The influence of the gap on the absorption performance of the conventional split ring resonator(SRR) absorber is investigated at microwave frequencies. Our simulated results reveal that the geometry of the square SRR can be equivalent to a Jerusalem cross(JC) resonator and its corresponding metamaterial absorber(MA) is changed to a JC absorber. The JC MA exhibits an experimental absorption peak of 99.1% at 8.72 GHz, which shows an excellent agreement with our simulated results. By simply assembling several JCs with slightly different geometric parameters next to each other into a unit cell, a perfect multi-band absorption can be effectively obtained. The experimental results show that the MA has four distinct and strong absorption peaks at 8.32 GHz, 9.8 GHz, 11.52 GHz and 13.24 GHz. Finally, the multi-reflection interference theory is introduced to interpret the absorption mechanism.展开更多
A multi-band absorber composed of high-permittivity hexagonal ring dielectric resonators and a metallic ground plate is designed in the microwave band. Near-unity absorptions around 9.785 GHz, 11.525 GHz, and 12.37 GH...A multi-band absorber composed of high-permittivity hexagonal ring dielectric resonators and a metallic ground plate is designed in the microwave band. Near-unity absorptions around 9.785 GHz, 11.525 GHz, and 12.37 GHz are observed for this metamaterial absorber. The dielectric hexagonal ring resonator is made of microwave ceramics with high permittivity and low loss. The mechanism for the near-unity absorption is investigated via the dielectric resonator theory. It is found that the absorption results from electric and magnetic resonances where enhanced electromagnetic fields are excited inside the dielectric resonator. In addition, the resonance modes of the hexagonal resonator are similar to those of standard rectangle resonators and can be used for analyzing hexagonal absorbers. Our work provides a new research method as well as a solid foundation for designing and analyzing dielectric metamaterial absorbers with complex shapes.展开更多
We develop a simple new design for a multi-band metamaterial absorber(MTMA)for radar applications.Computer Simulation Technology(CST)Studio Suite 2018 was used for the numerical analysis and absorption study.The simul...We develop a simple new design for a multi-band metamaterial absorber(MTMA)for radar applications.Computer Simulation Technology(CST)Studio Suite 2018 was used for the numerical analysis and absorption study.The simulated results show four high peaks at 5.6 GHz,7.6 GHz,10.98 GHz,and 11.29 GHz corresponding to absorption characteristics of 100%,100%,99%,and 99%,respectively.Furthermore,two different structures were designed and compared with the proposed MTMA.The proposed structure remained insensitive for any incident angle and polarization angle from 0°to60°.Moreover,negative constitutive parameters were retrieved numerically.To support the simulated results,the proposed design was fabricated by using a computer numerical control-based printed circuit board prototyping machine and tested experimentally in a microwave laboratory.The absorption mechanism of the proposed MTMA is presented through the surface current and electric field distributions.The novelties of the proposed structure are a simple and new design,ease of fabrication,low cost,durability,suitability for real-time applications and long-term stability given the fabrication technique and non-destructive measurement method and very high absorption.The proposed structure has potential applications in C and X band frequency ranges.展开更多
This study proposes a bi-layer windmill-shaped metamaterial that consists of resonators, with similar shapes, on both sides of a dielectric substrate. In this study, the second layer is rotated clockwise around the su...This study proposes a bi-layer windmill-shaped metamaterial that consists of resonators, with similar shapes, on both sides of a dielectric substrate. In this study, the second layer is rotated clockwise around the substrate normal at 90°and thereafter flipped in the first layer. Due to the introduction of a windmill-like shape, the resonant structures result in new resonant modes and thus can achieve multi-band high-efficiency cross-polarization conversions and asymmetric transmissions(ATs) for a linearly polarized incident plane wave with a maximum asymmetric parameter of 0.72. Depending on the geometric parameters of our windmill-shaped structures, the AT effects can be flexibly modulated in a broad multiband from 160 THz to 400 THz, which has not been reported in previous studies. These outstanding AT effects provide potential applications in optical diodes, polarization control switches, and other nano-devices.展开更多
To use the single split-ring resonator (SRR) as a basic unit cell for small antenna with multi-band frequency response is proposed. The structure of antenna is consisted of a single spilt-ring resonator and a couple...To use the single split-ring resonator (SRR) as a basic unit cell for small antenna with multi-band frequency response is proposed. The structure of antenna is consisted of a single spilt-ring resonator and a coupled microstrip line. The designed antenna is numerically optimized with CST Microwave Studio. The radiation properties of the antenna show that there are three frequency bands among which two bands are 1.3 GHz and 2.1 GHz ultra-widehand (UWB), respectively, where Sll is less than - 10 dB. The gain at every frequency for the multi-hand antenna is above 2.6 dBi, and it increases monotonously with the frequency in the two UWB.展开更多
A multi-band circular polarizer using a twisted triple split-ring resonator(TSRR) is presented and studied numerically and experimentally. At four distinct resonant frequencies, the incident linearly polarized wave ...A multi-band circular polarizer using a twisted triple split-ring resonator(TSRR) is presented and studied numerically and experimentally. At four distinct resonant frequencies, the incident linearly polarized wave can be transformed into left/right-handed circularly polarized waves. Numerical simulation results show that a y-polarized wave can be converted into a right-handed circularly polarized wave at 5.738 GHz and 9.218 GHz, while a left-handed circularly polarized wave is produced at 7.292 GHz and 10.118 GHz. The experimental results are in agreement with the numerical results. The surface current distributions are investigated to illustrate the polarization transformation mechanism. Furthermore, the influences of the structure parameters of the circular polarizer on transmission spectra are discussed as well.展开更多
We have studied the doping-driven orbital-selective Mott transition in multi-band Hubbard models with equal band width in the presence of crystal field splitting. Crystal field splitting lifts one of the bands while l...We have studied the doping-driven orbital-selective Mott transition in multi-band Hubbard models with equal band width in the presence of crystal field splitting. Crystal field splitting lifts one of the bands while leaving the others degener- ate. We use single-site dynamical mean-field theory combined with continuous time quantum Monte Carlo impurity solver to calculate a phase diagram as a function of total electron filling N and crystal field splitting A. We find a large region of orbital-selective Mott phase in the phase diagram when the doping is large enough. Further analysis indicates that the large region of orbital-selective Mott phase is driven and stabilized by doping. Such models may account for the orbital-selective Mott transition in some doped realistic strongly correlated materials.展开更多
This paper presents a compact multi-band rectifier with an improved impedance matching bandwidth.It uses a combination of–matching network(MN)at Port-1,with a parallel connection of three cell branch MN at Port-2.The...This paper presents a compact multi-band rectifier with an improved impedance matching bandwidth.It uses a combination of–matching network(MN)at Port-1,with a parallel connection of three cell branch MN at Port-2.The proposed impedance matching network(IMN)is adopted to reduce circuit complexity,to improve circuit performance,and power conversion efficiency(PCE)of the rectifier at low input power.The fabricated rectifier prototype operates at 0.92,1.82,2.1,2.46 and 2.65 GHz covering GSM/900,GSM/1800,UMTS2100,and Wi-Fi/2.45–LTE2600.The size of the compact rectifier on the PCB board is 0.13λ_(g)×0.1λ_(g).The fabricated rectifier achieved an RF-to DC(radio frequency direct current)PCE of 31.8%,24%,22.7%,and 15%,and 14.1%for−20 dBm at the five respective measured operating frequencies.The circuit attains a peak RF-to-DC PCE of 82.3%for an input power of 3 dBm at 0.92 GHz.The proposed rectifier realizes an ambient output dc voltage of 454 mV for multi-tone input signals from the two ports.The rectifier drives a bq25504-674 power management module(PMM)to achieve 1.21 V from the two-port connection.The rectifier has the ability to exploit both frequency domain through the multi-band operation with good impedance bandwidth and a spatial domain using dual-port configuration.Hence,it is a potential candidate for various applications in radio frequency energy harvesting(RFEH)system.展开更多
A novel multi-band end-fire antenna array was designed, fabricated, and characterized. Analytical calculations were carried out to determine the critical antenna dimensions and the design was optimized using a 3D elec...A novel multi-band end-fire antenna array was designed, fabricated, and characterized. Analytical calculations were carried out to determine the critical antenna dimensions and the design was optimized using a 3D electromagnetic finite-element solver. The measured results were in good agreement with the designed results. The proposed antenna array exhibits multi-band capabilities which can be potentially used for applications that require a multi-band end-fire radiation pattern.展开更多
The paper proposes a new method of multi-band signal reconstruction based on Orthogonal Matching Pursuit(OMP),which aims to develop a robust Ecological Sounds Recognition(ESR)system.Firstly,the OMP is employed to spar...The paper proposes a new method of multi-band signal reconstruction based on Orthogonal Matching Pursuit(OMP),which aims to develop a robust Ecological Sounds Recognition(ESR)system.Firstly,the OMP is employed to sparsely decompose the original signal,thus the high correlation components are retained to reconstruct in the first stage.Then,according to the frequency distribution of both foreground sound and background noise,the signal can be compensated by the residual components in the second stage.Via the two-stage reconstruction,high non-stationary noises are effectively reduced,and the reconstruction precision of foreground sound is improved.At recognition stage,we employ deep belief networks to model the composite feature sets extracted from reconstructed signal.The experimental results show that the proposed approach achieved superior recognition performance on 60 classes of ecological sounds in different environments under different Signal-to-Noise Ratio(SNR),compared with the existing method.展开更多
This paper proposes a multi-band speech enhancement algorithm exploiting iterative processing for enhancement of single channel speech. In the proposed algorithm, the output of the multi-band spectral subtraction (MBS...This paper proposes a multi-band speech enhancement algorithm exploiting iterative processing for enhancement of single channel speech. In the proposed algorithm, the output of the multi-band spectral subtraction (MBSS) algorithm is used as the input signal again for next iteration process. As after the first MBSS processing step, the additive noise transforms to the remnant noise, the remnant noise needs to be further re-estimated. The proposed algorithm reduces the remnant musical noise further by iterating the enhanced output signal to the input again and performing the operation repeatedly. The newly estimated remnant noise is further used to process the next MBSS step. This procedure is iterated a small number of times. The proposed algorithm estimates noise in each iteration and spectral over-subtraction is executed independently in each band. The experiments are conducted for various types of noises. The performance of the proposed enhancement algorithm is evaluated for various types of noises at different level of SNRs using, 1) objective quality measures: signal-to-noise ratio (SNR), segmental SNR, perceptual evaluation of speech quality (PESQ);and 2) subjective quality measure: mean opinion score (MOS). The results of proposed enhancement algorithm are compared with the popular MBSS algorithm. Experimental results as well as the objective and subjective quality measurement test results confirm that the enhanced speech obtained from the proposed algorithm is more pleasant to listeners than speech enhanced by classical MBSS algorithm.展开更多
This paper presents the design and the experimental characterization of a new multi-band antenna consisting of three folded monopoles dedicated to mobile communication systems. The originality of this paper is to get ...This paper presents the design and the experimental characterization of a new multi-band antenna consisting of three folded monopoles dedicated to mobile communication systems. The originality of this paper is to get the PMR (Professional or Private Mobile Radio) band with the GSM (Global System for Mobile Communications), DCS (Digital Cellular System) and UMTS (Universal Mobile Telecommunications System) bands. The main lobe of the antenna radiates in the zenith direction with a linear polarization over all bands. It is interesting to design the proposed antenna in order to obtain better performances in terms of directive radiation pattern (especially in the PMR band) in comparison with the already existing antenna systems in the wireless market for similar purposes. The prototype was studied with the software CST-MWS (Micro wave studio 2012). The antenna has been designed and successfully measured.展开更多
基金the Deanship of Scientific Research at Imam Mohammad Ibn Saud Islamic University for funding this work through Research Group No.RG-21–12–08.The initials of authors who receive the Grant are:ZAS.The URL of the sponsor’s website:https://units.imamu.edu.sa/deanships/sr/Pages/default.aspx.
文摘A multi-band metamaterial antenna is proposed to operate at the terahertz(THz)band for medical applications.The proposed structure is designed on a polyimide as a support layer,and its radiating elements are made of graphene.Initially,the design is started with a conventional shape showing a single operating frequency at 1.1 THz.To achieve a multi-band operating frequency,the conventional shape was replaced with the proposed metamaterial as a radiating patch that has properties not exist in nature.The multi-band frequencies are obtained without compromising the overall size of the design.The overall size is 600×600×25μm^(3).The operating frequencies are 0.36,0.49,0.69,0.87,and 1.04 THz.A full ground plane is used to behave as isolation between the design and the human body model.The proposed design is investigated on free space and on the human body model,showing excellent performance in both cases.The achieved gains for the following frequencies 0.36,0.49,0.69,0.87,and 1.04 THz are 4.81,6.5,8.41,6.02,and 7.96 dB,respectively,while the efficiencies are 83.91%,96.28%,90.80%,91.71%,and 92.99%,respectively.The conventional design was modified to have a partial ground to show the benefit of using the full ground.The design is loaded on the human body model and its performance is affected.The efficiency and gain are 6.61 dB and 95.58.7%for the case of no human body model,and 4.26 dB and 40.30%for the case of using a human body model.Hence,the proposed metamaterial antenna will be useful for future medical applications in the THz band.
基金supported by National Natural Science Foundation of China(No.12075281)the National Magnetic Confinement Fusion Research Program of China(Nos.2017YFE0301104 and 2017YFE0301105)Important Projects of Collaborative Innovation of the Hefei Science Center,CAS(No.2021HSC-CIP007)。
文摘A new multi-band and high-speed endoscope diagnostic for the observation of visible light has been successfully developed on the Experimental Advanced Superconducting Tokamak.The mirror with an aperture is designed at the head of the optical system.Based on two dichroic mirrors,the system is divided into three imaging mirror groups with different bands,i.e.B(380-500 nm),G(500-580 nm)and R(580-750 nm)bands,and its focal length is 16 mm with a relatively large aperture of D/f=1:4.The spatial resolution is less than 5 mm near the object distance of 1750 mm with the camera NAC ACS-1 M60.This optical system will be used to contrastively study both the spatial distribution and time evolution of different impurities in the same field of view.The experimental results confirm that it can be applied to the recognition of plasma boundary and related physical research.
文摘The property of multi-band operation has been studied and investigated analytically through the design of a rectangular patch microstrip antenna having different numbers of wide slots arranged at both the radiating edges. The analyses were carried out using the method of moments simulation software. It is shown that a patch with three slots has a multi-band feature with four resonant frequencies at 1.6, 1.8, 2.65, and 4.83 GHz and adequate values of return loss and gain. It is also shown that a patch with two pairs of wide slots arranged at both the radiating edges has the dual band feature with resonant frequencies at 1.64 and 1.8 GHz and good values of return loss and gain.
基金supported by the Beijing Natural Science Foundation of China (4102050)
文摘Cognitive radio(CR) technology is considered to be an effective solution to allocate spectrum resources,whereas the primary users of a network do not fully utilize available frequency bands.Spectrum auction framework has been recognized as an effective way to achieve dynamic spectrum access.From the perspective of spectrum auction,multi-band multi-user auction provides a new challenge for spectrum management.This paper proposes an auction framework based on location information for multi-band multi-user spectrum allocation.The performance of the proposed framework is compared with that of traditional auction framework based on a binary interference model as a benchmark.Simulation results show that primary users will obtain more total system revenue by selling their idle frequency bands to secondary users and the spectrum utilization of the proposed framework is more effective and fairer.
文摘This analysis focuses on PIM interference under multi-band multi-signal input in mobile communication system.Unlike single band system that only odd order PIM(especially 3rd order) should be concerned,in multi-band multi-signal case,both odd and even order PIM could be interference source because of more complicated intermodulation,more IMPs generated and more receive bands.Especially,the 2nd order PIM may interfere more serious to receiving channel for its strong magnitude.In duplex indoor distribute system,the PIM interference is a potential problem to GSM900,DCS1800,CDMA,and even 3G system wireless services,because the PIM frequencies may fall in receive bands and interfere to the receiving channels.In radio system design and wireless channel assignment,precautions must be taken to minimize the PIM level and to avoid interfere to receiving channels.For practical use,the lower order possible PIM interference to 2G and 3G systems is calculated.
基金Project supported by the School Youth Fund of Henan University of Science and Technology(Grant No.2014QN045)。
文摘We present a high-efficiency tunable wide-angle multi-band reflective linear-to-linear(LTL)polarization converter,which is composed of an array of two L-shaped graphene patches with different sizes.In the mid-infrared region,the proposed converter can transform x-polarized wave into y-polarized wave at four resonant frequencies.The polarization conversion ratios of the four bands reach 94.4%,92.7%,99.3%,and 93.1%,respectively.By carefully choosing the geometric parameter,triple-band LTL polarization conversion can also be realized.The three polarization conversion ratios reach 91.50%,99.20%,and 97.22%,respectively.The influence of incident angle on the performances of the LTL polarization converter is investigated,and it is found that our polarization converter shows the angle insensitivity.Also,the dynamically tunable properties of the proposed polarization converter are numerically studied by changing Fermi energy.All the simulation results are conducted by finite element method.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61471389,61701523,and 61671464)
文摘In this paper, a multi-band metasurface(MS) antenna array with low radar cross section(RCS) performance is proposed and measured. Firstly, a 44 antenna array is composed of four 22 Jerusalem cross structure antenna arrays working at different frequency bands, which is aimed at enhancing the bandwidth effectively. Then, each antenna can be seen as a unit of MS in spite of adding the feeding structure. Based on phase cancellation principle, the MS is arranged into a chessboard configuration in order to realize wideband RCS reduction. Thus, excellent radiation and scattering characteristics are obtained simultaneously. Simulated and measured results indicate that this work provides a novel method to achieve bandwidth expansion as well as wideband RCS reduction of the antenna array.
基金supported by the National Natural Science Foundation of China(90305026).
文摘Traditional multi-band frequency selective surface (FSS) approaches are hard to achieve a perfect resonance response in a wide band due to the limit of the onset grating lobe frequency determined by the array. To solve this problem, an approach of combining elements in different period to build a hybrid array is presented. The results of series of numerical simulation show that multi-periodicity combined element FSS, which are designed using this approach, usually have much weaker grating lobes than the traditional FSS. Furthermore, their frequency response can be well predicted through the properties of their member element FSS. A prediction method for estimating the degree of expected grating lobe energy loss in designing multi-band FSS using this approach is provided.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10775055 and 11105002) and the Open-end Fund of State Key Laboratory of Structural Analysis for Industrial Equipment, China (Grant No. GZ 1215).
文摘The influence of the gap on the absorption performance of the conventional split ring resonator(SRR) absorber is investigated at microwave frequencies. Our simulated results reveal that the geometry of the square SRR can be equivalent to a Jerusalem cross(JC) resonator and its corresponding metamaterial absorber(MA) is changed to a JC absorber. The JC MA exhibits an experimental absorption peak of 99.1% at 8.72 GHz, which shows an excellent agreement with our simulated results. By simply assembling several JCs with slightly different geometric parameters next to each other into a unit cell, a perfect multi-band absorption can be effectively obtained. The experimental results show that the MA has four distinct and strong absorption peaks at 8.32 GHz, 9.8 GHz, 11.52 GHz and 13.24 GHz. Finally, the multi-reflection interference theory is introduced to interpret the absorption mechanism.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61331005,11204378,11274389,11304393,and 61302023)the Aviation Science Foundation of China(Grant Nos.20132796018 and 20123196015)+2 种基金the Natural Science Foundation for Post-Doctoral Scientists of China(Grant Nos.2013M532131 and 2013M532221)the Natural Science Foundation of Shaanxi Province,China(Grant No.2013JM6005)the Special Funds for Authors of Annual Excellent Doctoral Degree Dissertations of China(Grant No.201242)
文摘A multi-band absorber composed of high-permittivity hexagonal ring dielectric resonators and a metallic ground plate is designed in the microwave band. Near-unity absorptions around 9.785 GHz, 11.525 GHz, and 12.37 GHz are observed for this metamaterial absorber. The dielectric hexagonal ring resonator is made of microwave ceramics with high permittivity and low loss. The mechanism for the near-unity absorption is investigated via the dielectric resonator theory. It is found that the absorption results from electric and magnetic resonances where enhanced electromagnetic fields are excited inside the dielectric resonator. In addition, the resonance modes of the hexagonal resonator are similar to those of standard rectangle resonators and can be used for analyzing hexagonal absorbers. Our work provides a new research method as well as a solid foundation for designing and analyzing dielectric metamaterial absorbers with complex shapes.
文摘We develop a simple new design for a multi-band metamaterial absorber(MTMA)for radar applications.Computer Simulation Technology(CST)Studio Suite 2018 was used for the numerical analysis and absorption study.The simulated results show four high peaks at 5.6 GHz,7.6 GHz,10.98 GHz,and 11.29 GHz corresponding to absorption characteristics of 100%,100%,99%,and 99%,respectively.Furthermore,two different structures were designed and compared with the proposed MTMA.The proposed structure remained insensitive for any incident angle and polarization angle from 0°to60°.Moreover,negative constitutive parameters were retrieved numerically.To support the simulated results,the proposed design was fabricated by using a computer numerical control-based printed circuit board prototyping machine and tested experimentally in a microwave laboratory.The absorption mechanism of the proposed MTMA is presented through the surface current and electric field distributions.The novelties of the proposed structure are a simple and new design,ease of fabrication,low cost,durability,suitability for real-time applications and long-term stability given the fabrication technique and non-destructive measurement method and very high absorption.The proposed structure has potential applications in C and X band frequency ranges.
基金Project supported by the National Youth Foundation of China(Grant Nos.11904200 and 11704219)the National Natural Science Foundation of China(Grant No.11774053)+3 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20190726)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.18KJD140004)NJUPT-SF(Grant No.NY218099)the Opening Project of the Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology(Grant No.hxkj2019007).
文摘This study proposes a bi-layer windmill-shaped metamaterial that consists of resonators, with similar shapes, on both sides of a dielectric substrate. In this study, the second layer is rotated clockwise around the substrate normal at 90°and thereafter flipped in the first layer. Due to the introduction of a windmill-like shape, the resonant structures result in new resonant modes and thus can achieve multi-band high-efficiency cross-polarization conversions and asymmetric transmissions(ATs) for a linearly polarized incident plane wave with a maximum asymmetric parameter of 0.72. Depending on the geometric parameters of our windmill-shaped structures, the AT effects can be flexibly modulated in a broad multiband from 160 THz to 400 THz, which has not been reported in previous studies. These outstanding AT effects provide potential applications in optical diodes, polarization control switches, and other nano-devices.
基金Sponsored by the BIT Developing Foundation(1070050320726)
文摘To use the single split-ring resonator (SRR) as a basic unit cell for small antenna with multi-band frequency response is proposed. The structure of antenna is consisted of a single spilt-ring resonator and a coupled microstrip line. The designed antenna is numerically optimized with CST Microwave Studio. The radiation properties of the antenna show that there are three frequency bands among which two bands are 1.3 GHz and 2.1 GHz ultra-widehand (UWB), respectively, where Sll is less than - 10 dB. The gain at every frequency for the multi-hand antenna is above 2.6 dBi, and it increases monotonously with the frequency in the two UWB.
基金Project supported by the National Natural Science Foundation of China(Grant No.41474117)the Special Funds for Development Scientific Research Unit Projects of Wuhan,China(Grant No.2013BJ004)
文摘A multi-band circular polarizer using a twisted triple split-ring resonator(TSRR) is presented and studied numerically and experimentally. At four distinct resonant frequencies, the incident linearly polarized wave can be transformed into left/right-handed circularly polarized waves. Numerical simulation results show that a y-polarized wave can be converted into a right-handed circularly polarized wave at 5.738 GHz and 9.218 GHz, while a left-handed circularly polarized wave is produced at 7.292 GHz and 10.118 GHz. The experimental results are in agreement with the numerical results. The surface current distributions are investigated to illustrate the polarization transformation mechanism. Furthermore, the influences of the structure parameters of the circular polarizer on transmission spectra are discussed as well.
基金Project supported by the National Natural Science Foundation of China(Grant No.2011CBA00108)the National Basic Research Program of China(Grant No.2013CB921700)
文摘We have studied the doping-driven orbital-selective Mott transition in multi-band Hubbard models with equal band width in the presence of crystal field splitting. Crystal field splitting lifts one of the bands while leaving the others degener- ate. We use single-site dynamical mean-field theory combined with continuous time quantum Monte Carlo impurity solver to calculate a phase diagram as a function of total electron filling N and crystal field splitting A. We find a large region of orbital-selective Mott phase in the phase diagram when the doping is large enough. Further analysis indicates that the large region of orbital-selective Mott phase is driven and stabilized by doping. Such models may account for the orbital-selective Mott transition in some doped realistic strongly correlated materials.
基金supported by TM R&D Malaysia under project number MMUE/190001.
文摘This paper presents a compact multi-band rectifier with an improved impedance matching bandwidth.It uses a combination of–matching network(MN)at Port-1,with a parallel connection of three cell branch MN at Port-2.The proposed impedance matching network(IMN)is adopted to reduce circuit complexity,to improve circuit performance,and power conversion efficiency(PCE)of the rectifier at low input power.The fabricated rectifier prototype operates at 0.92,1.82,2.1,2.46 and 2.65 GHz covering GSM/900,GSM/1800,UMTS2100,and Wi-Fi/2.45–LTE2600.The size of the compact rectifier on the PCB board is 0.13λ_(g)×0.1λ_(g).The fabricated rectifier achieved an RF-to DC(radio frequency direct current)PCE of 31.8%,24%,22.7%,and 15%,and 14.1%for−20 dBm at the five respective measured operating frequencies.The circuit attains a peak RF-to-DC PCE of 82.3%for an input power of 3 dBm at 0.92 GHz.The proposed rectifier realizes an ambient output dc voltage of 454 mV for multi-tone input signals from the two ports.The rectifier drives a bq25504-674 power management module(PMM)to achieve 1.21 V from the two-port connection.The rectifier has the ability to exploit both frequency domain through the multi-band operation with good impedance bandwidth and a spatial domain using dual-port configuration.Hence,it is a potential candidate for various applications in radio frequency energy harvesting(RFEH)system.
文摘A novel multi-band end-fire antenna array was designed, fabricated, and characterized. Analytical calculations were carried out to determine the critical antenna dimensions and the design was optimized using a 3D electromagnetic finite-element solver. The measured results were in good agreement with the designed results. The proposed antenna array exhibits multi-band capabilities which can be potentially used for applications that require a multi-band end-fire radiation pattern.
基金Supported by the National Natural Science Foundation of China(No.61075022)
文摘The paper proposes a new method of multi-band signal reconstruction based on Orthogonal Matching Pursuit(OMP),which aims to develop a robust Ecological Sounds Recognition(ESR)system.Firstly,the OMP is employed to sparsely decompose the original signal,thus the high correlation components are retained to reconstruct in the first stage.Then,according to the frequency distribution of both foreground sound and background noise,the signal can be compensated by the residual components in the second stage.Via the two-stage reconstruction,high non-stationary noises are effectively reduced,and the reconstruction precision of foreground sound is improved.At recognition stage,we employ deep belief networks to model the composite feature sets extracted from reconstructed signal.The experimental results show that the proposed approach achieved superior recognition performance on 60 classes of ecological sounds in different environments under different Signal-to-Noise Ratio(SNR),compared with the existing method.
文摘This paper proposes a multi-band speech enhancement algorithm exploiting iterative processing for enhancement of single channel speech. In the proposed algorithm, the output of the multi-band spectral subtraction (MBSS) algorithm is used as the input signal again for next iteration process. As after the first MBSS processing step, the additive noise transforms to the remnant noise, the remnant noise needs to be further re-estimated. The proposed algorithm reduces the remnant musical noise further by iterating the enhanced output signal to the input again and performing the operation repeatedly. The newly estimated remnant noise is further used to process the next MBSS step. This procedure is iterated a small number of times. The proposed algorithm estimates noise in each iteration and spectral over-subtraction is executed independently in each band. The experiments are conducted for various types of noises. The performance of the proposed enhancement algorithm is evaluated for various types of noises at different level of SNRs using, 1) objective quality measures: signal-to-noise ratio (SNR), segmental SNR, perceptual evaluation of speech quality (PESQ);and 2) subjective quality measure: mean opinion score (MOS). The results of proposed enhancement algorithm are compared with the popular MBSS algorithm. Experimental results as well as the objective and subjective quality measurement test results confirm that the enhanced speech obtained from the proposed algorithm is more pleasant to listeners than speech enhanced by classical MBSS algorithm.
文摘This paper presents the design and the experimental characterization of a new multi-band antenna consisting of three folded monopoles dedicated to mobile communication systems. The originality of this paper is to get the PMR (Professional or Private Mobile Radio) band with the GSM (Global System for Mobile Communications), DCS (Digital Cellular System) and UMTS (Universal Mobile Telecommunications System) bands. The main lobe of the antenna radiates in the zenith direction with a linear polarization over all bands. It is interesting to design the proposed antenna in order to obtain better performances in terms of directive radiation pattern (especially in the PMR band) in comparison with the already existing antenna systems in the wireless market for similar purposes. The prototype was studied with the software CST-MWS (Micro wave studio 2012). The antenna has been designed and successfully measured.