Design of a photonic crystal fiber polarization beam splitter with simple structure and ultra-wide bandwidth

A novel polarization beam splitter(PBS)based on dual-core photonic crystal fiber(DC-PCF)is proposed in this work.The proposed DC-PCF PBS contains two kinds of lattices and three kinds of air holes to form the asymmetrical elliptic dual-core structure.By using the full-vector finite element method,the propagation characteristics of the proposed DC-PCF PBS are investigated.The simulation results show that the bandwidth of the proposed DC-PCF PBS can reach to 340 nm,which covers the S+C+L+U communication bands,the shortest splitting length is 1.97 mm,and the maximum extinction ratio appears near wavelength 1550 nm.Moreover,the insertion loss of the proposed DC-PCF PBS is very low.It is believed that the proposed DC-PCF PBS has important applications in the field of all-optical communication and network.

Novel indoor positioning system based on ultra-wide bandwidth

To tackle challenges such as interference and poor accuracy of indoor positioning systems,a novel scheme based on ultra-wide bandwidth(UWB)technology is proposed.First,we illustrate a distance measuring method between two UWB devices.Then,a Taylor series expansion algorithm is developed to detect coordinates of the mobile node using the location of anchor nodes and the distance between them.Simulation results show that the observation error under our strategy is within 15 cm,which is superior to existing algorithms.The final experimental data in the hardware system mainly composed of STM32 and DW1000 also confirms the performance of the proposed scheme.

一种改进的数字Ultra-Wide Bandwidth Radio-on-Fiber系统模型的性能分析

为了充分利用超宽带的特点,对数字光载无线系统进行了改进,并给出了系统模型.理论分析和仿真结果表明,跳时序列构造不同,系统性能(信噪比)也不同;相同构造下,激活用户数不同引起的时隙平均干扰也不同.这种改进使得数字光载无线系统降低了复杂度,提高了光纤利用率,同时也改善了系统的性能.

Retinal vascular morphological characteristics in diabetic retinopathy: an artificial intelligence study using a transfer learning system to analyze ultra-wide field images

AIM:To investigate the morphological characteristics of retinal vessels in patients with different severity of diabetic retinopathy(DR)and in patients with or without diabetic macular edema(DME).METHODS:The 239 eyes of DR patients and 100 eyes of healthy individuals were recruited for the study.The severity of DR patients was graded as mild,moderate and severe non-proliferative diabetic retinopathy(NPDR)according to the international clinical diabetic retinopathy(ICDR)disease severity scale classification,and retinal vascular morphology was quantitatively analyzed in ultra-wide field images using RU-net and transfer learning methods.The presence of DME was determined by optical coherence tomography(OCT),and differences in vascular morphological characteristics were compared between patients with and without DME.RESULTS:Retinal vessel segmentation using RU-net and transfer learning system had an accuracy of 99%and a Dice metric of 0.76.Compared with the healthy group,the DR group had smaller vessel angles(33.68±3.01 vs 37.78±1.60),smaller fractal dimension(Df)values(1.33±0.05 vs 1.41±0.03),less vessel density(1.12±0.44 vs 2.09±0.36)and fewer vascular branches(206.1±88.8 vs 396.5±91.3),all P<0.001.As the severity of DR increased,Df values decreased,P=0.031.No significant difference between the DME and non-DME groups were observed in vascular morphological characteristics.CONCLUSION:In this study,an artificial intelligence retinal vessel segmentation system is used with 99%accuracy,thus providing with relatively satisfactory performance in the evaluation of quantitative vascular morphology.DR patients have a tendency of vascular occlusion and dropout.The presence of DME does not compromise the integral retinal vascular pattern.

Prediction of Bandwidth of Metamaterial Antenna Using Pearson Kernel-Based Techniques

The use of metamaterial enhances the performance of a specific class of antennas known as metamaterial antennas.The radiation cost and quality factor of the antenna are influenced by the size of the antenna.Metamaterial antennas allow for the circumvention of the bandwidth restriction for small antennas.Antenna parameters have recently been predicted using machine learning algorithms in existing literature.Machine learning can take the place of the manual process of experimenting to find the ideal simulated antenna parameters.The accuracy of the prediction will be primarily dependent on the model that is used.In this paper,a novel method for forecasting the bandwidth of the metamaterial antenna is proposed,based on using the Pearson Kernel as a standard kernel.Along with these new approaches,this paper suggests a unique hypersphere-based normalization to normalize the values of the dataset attributes and a dimensionality reduction method based on the Pearson kernel to reduce the dimension.A novel algorithm for optimizing the parameters of Convolutional Neural Network(CNN)based on improved Bat Algorithm-based Optimization with Pearson Mutation(BAO-PM)is also presented in this work.The prediction results of the proposed work are better when compared to the existing models in the literature.

An extended state observer with adjustable bandwidth for measurement noise

In this paper,a bandwidth-adjustable extended state observer(ABESO)is proposed for the systems with measurement noise.It is known that increasing the bandwidth of the observer improves the tracking speed but tolerates noise,which conflicts with observation accuracy.Therefore,we introduce a bandwidth scaling factor such that ABESO is formulated to a 2-degree-of-freedom system.The observer gain is determined and the bandwidth scaling factor adjusts the bandwidth according to the tracking error.When the tracking error decreases,the bandwidth decreases to suppress the noise,otherwise the bandwidth does not change.It is proven that the error dynamics are bounded and converge in finite time.The relationship between the upper bound of the estimation error and the scaling factor is given.When the scaling factor is less than 1,the ABESO has higher estimation accuracy than the linear extended state observer(LESO).Simulations of an uncertain nonlinear system with compound disturbances show that the proposed ABESO can successfully estimate the total disturbance in noisy environments.The mean error of total disturbance of ABESO is 15.28% lower than that of LESO.

Compact Coplanar Epsilon-Negative Antenna with Ultra-Wide Band Character

In this paper, a compact coplanar epsilon.negative(ENG) antenna is proposed with ultra.wide operation band and small size of 18×11.5 mm2. The proposed antenna is designed based on a coplanar.waveguide(CPW) feeding antenna, and thus the via.free structure is employed to realize the ENG unit cell, which is convenient to tune the frequency of zeroth.order resonance(ZOR) and extends the ZOR bandwidth. The high.order resonant frequencies are achieved and mainly determined by the separate slots that are located between the radiating patch and the ground plane. Adding the left.handed inductance between the radiating patch and ground has slight impact on the high.order resonant frequencies, and then the ultra.wide band is achieved by merging the ZOR bandwidth with the high.order resonant bandwidths. The ground plane primarily works as a matching network for the proposed antenna. Although it generates a low.frequency resonance, the performance is undesirable due to the impedance mismatching. The measured results show that the reflection coefficient, |S11| <.10 d B, is in a wide frequency range from 5.25 to 13 GHz, which covers the upper operation band of UWB communication. Also, the antenna contains relatively stable gains and omni.directional radiation patterns.

Progress of power field effect transistor based on ultra-wide bandgap Ga_2O_3 semiconductor material

As a promising ultra-wide bandgap semiconductor, gallium oxide(Ga_2O_3) has attracted increasing attention in recent years. The high theoretical breakdown electrical field(8 MV/cm), ultra-wide bandgap(～ 4.8 eV) and large Baliga's figure of merit(BFOM) of Ga_2O_3 make it a potential candidate material for next generation high-power electronics, including diode and field effect transistor(FET). In this paper, we introduce the basic physical properties of Ga_2O_3 single crystal, and review the recent research process of Ga_2O_3 based field effect transistors. Furthermore, various structures of FETs have been summarized and compared, and the potential of Ga_2O_3 is preliminary revealed. Finally, the prospect of the Ga_2O_3 based FET for power electronics application is analyzed.

Fractal analysis of retinal vasculature in normal subjects on ultra-wide field fluorescein angiography

AIM: To evaluate the fractal feature of the retinal vasculature of normal eyes on a stereographic projected and montaged ultra-wide field(UWF) fluorescein angiography(FA).METHODS: Prospective, observational, cross-sectional study. Totally 59 eyes of 31 normal subjects were imaged using the Optos 200 Tx. Images obtained at different gaze angles stereographically projected and montaged. The early-phase UWF FA frames were processed to segment the retinal vasculature and the results were exported as binary masks. The fractal dimension(FD) was calculated using the box-counting method.RESULTS: The global FD for the entire retina was 1.6±0.04, with no difference between males and females(1.59±0.04 vs 1.61±0.04, P=0.084) or between right and left eyes(1.6±0.04 vs 1.6±0.05, P=0.61). FD was nonuniformly distributed among four quadrants(P<0.001) and decreased as the distance from the fovea increased(P<0.001). A negative association was observed between FD and age(R=-0.37, P=0.006), and this relationship was observed in the posterior and mid-peripheral retina(P<0.05) but absent in far-periphery(P>0.05).CONCLUSION: Fractal geometry is non-uniformly distributed across the retina in normal eyes and decreases from the fovea to the far-periphery. Subjects with an older age tend to have a smaller FD, however, the FD in the farperiphery does not appear to be influenced by age.

An ultra-wideband pattern reconflgurable antenna based on graphene coating

An ultra-wideband pattern reconfigurable antenna is proposed.The antenna is a dielectric coaxial hollow monopole with a cylindrical graphene-based impedance surface coating.It consists of a graphene sheet coated onto the inner surface of a cylindrical substrate and a set of independent polysilicon DC gating pads mounted on the outside of the cylindrical substrate.By changing the DC bias voltages to the different gating pads,the surface impedance of the graphene coating can be freely controlled.Due to the tunability of graphene＇s surface impedance,the radiation pattern of the proposed antenna can be reconfigured.A transmission line method is used to illustrate the physical mechanism of the proposed antenna.The results show that the proposed antenna can reconfigure its radiation pattern in the omnidirectional mode with the relative bandwidth of 58.5% and the directional mode over the entire azimuth plane with the relative bandwidth of 67%.

Ultra-wideband RCS reduction using novel configured chessboard metasurface

A novel artificial magnetic conductor（AMC） metasurface is proposed with ultra-wideband 180？phase difference for radar cross section（RCS） reduction. It is composed of two dual-resonant AMC cells, which enable a broadband phase difference of 180°±30°from 7.9 GHz to 19.2 GHz to be achieved. A novel strategy is devised by dividing each rectangular grid in a chessboard configuration into four triangular grids, leading to a further reduction of peak bistatic RCS. Both fullwave simulation and measurement results show that the proposed metasurface presents a good RCS reduction property over an ultra-wideband frequency range.

Preface to the Special Issue on Ultra-Wide Bandgap Semiconductor Gallium Oxide: from Materials to Devices

As one of the ultra-wide bandgap {UWBG)semiconducting materials,gallium oxide has attractive properties with a wide bandgap of about 4.8 eV and a high breakdown field of about 8 MWcm,which offers an alternative platform for various applications such as high performance power switches,RF amplifiers,solar blind photodetectors,and harsh environment signal processing.

Ultra-wideband Frequency Selective Surface for Communication Applications

A low-profile ultra-wideband(UWB)band-stop frequency selective surface(FSS)is designed for S-,C-,X-and Ku-bands communication applications.The FSS is constructed by using square and circular loop elements printed on the top and bottom sides of the RO3210 substrate.The FSS has been designed to reduce the electromagnetic interference(EMI)as well as to mitigate the harmful effects of electromagnetic radiation on the human body caused by different radio devices.The dimension and size of the UWB FSS have been reduced to 0.12λ×0.12λand 90%,respectively,as compared to the reported literature.The other advantages of the proposed FSS are that it is low profile,it has a simplified geometry and it ensures better angular and polarization stability of up to 85◦.The-10 and-20 dB bandwidths of the proposed FSS are 146%(2.0-13.0 GHz)and 80%(4.87-11.42 GHz),respectively.Theoretical results have been obtained using ANSYS HFSS and verified through measured results.

A Compact Rhombus Shaped Antenna with Extended Stubs for Ultra-Wideband Applications

Ultra-wideband(UWB)is highly preferred for short distance communication.As a result of this significance,this project targets the design of a compact UWB antennas.This paper describes a printed UWB rhombusshaped antenna with a partial ground plane.To achieve wideband response,two stubs and a notch are incorporated at both sides of the rhombus design and ground plane respectively.To excite the antenna,a simple microstrip feed line is employed.The suggested antenna is built on a 1.6 mm thick FR4 substrate.The proposed design is very compact with overall electrical size of 0.18λ×0.25λ(14×18 mm2).The rhombus shaped antenna covers frequency ranging from 3.5 to 11 GHz with 7.5 GHz impedance bandwidth.The proposed design simulated and measured bandwidths are 83.33%and 80%,respectively.Radiation pattern in terms of E-field and H-field are discussed at 4,5.5 and 10 GHz respectively.The proposed design has 65%radiation efficiency and 1.5 dBi peak gain.The proposed design is simulated in CST(Computer Simulation Technology)simulator and the simulated design is fabricated for the measured results.The simulated and measured findings are in close resemblance.The obtained results confirm the application of the proposed design for the ultra-wide band applications.

Evaluation of traumatic retinopathy with ultra-wide field imaging under corneal scar or fixed small pupil

AIM： To evaluate the value of ultra-wide field（UWF） imaging in the management of traumatic retinopathy under the condition of corneal scar or fixed small pupil after complicated ocular trauma. METHODS： Twenty-eight patients（28 eyes） with complicated ocular trauma were enrolled in the study from June 2016 to May 2017, including 19 males and 9 females with age ranged from 11 to 64（43.42±12.62）y. All patients were treated with secondary vitrectomy after emergency operation for wound repair of open ocular trauma. Direct ophthalmoscopy and 45-degree fundus photography were taken at each time point of follow up for comparison of findings with UWF images. Routine eye examination including visual acuity, intraocular pressure, slit lamp examination were performed and analyzed as well.RESULTS： Among the 28 traumatized eyes, the positive rate for identification of traumatic retinopathed was 32.1%（9 cases）, 14.9%（5 cases）, and 85.7%（24 cases） with direct ophthalmoscopy, 45-degree fundus photography, and UWF imaging, respectively. The detective rate of UWF imaging under the condition of corneal scar or fixed small pupil was statistically greater than that of 45-degree fundus photography and direct ophthalmoscopy（Bonferroni correction, P〈0.001）. UWF image was obtained in 19 eyes with opaque corneal scar, otherwise their fundus could not be seen by conventional methods. The additional findings of traumatic retinopathies by UWF imaging included periretinal membranes or pre-retinal proliferating strip, retinal holes, hemorrhage in the vitreous or sub-retinal space.CONCLUSION： UWF imaging is superior to traditional fundus photography in the evaluation of traumatic retinopathies under the condition of corneal scar or fixed small pupil after complicated ocular trauma.

Initiating Binary Metal Oxides Microcubes Electromagnetic Wave Absorber Toward Ultrabroad Absorption Bandwidth Through Interfacial and Defects Modulation

Cobalt nickel bimetallic oxides(NiCo_(2)O_(4))have received numerous attentions in terms of their controllable morphology,high temperature,corrosion resistance and strong electromagnetic wave(EMW)absorption capability.However,broadening the absorption bandwidth is still a huge challenge for NiCo_(2)O_(4)-based absorbers.Herein,the unique NiCo_(2)O_(4)@C core-shell microcubes with hollow structures were fabricated via a facile sacrificial template strategy.The concentration of oxygen vacancies and morphologies of the three-dimensional(3D)cubic hollow core-shell NiCo_(2)O_(4)@C framework were effectively optimized by adjusting the calcination temperature.The specially designed 3D framework structure facilitated the multiple reflections of incident electromagnetic waves and provided rich interfaces between multiple components,generating significant interfacial polarization losses.Dipole polarizations induced by oxygen vacancies could further enhance the attenuation ability for the incident EM waves.The optimized NiCo_(2)O_(4)@C hollow microcubes exhibit superior EMW absorption capability with minimum RL(RLmin)of-84.45 dB at 8.4 GHz for the thickness of 3.0 mm.Moreover,ultrabroad effective absorption bandwidth(EAB)as large as 12.48 GHz(5.52-18 GHz)is obtained.This work is believed to illuminate the path to synthesis of high-performance cobalt nickel bimetallic oxides for EMW absorbers with excellent EMW absorption capability,especially in broadening effective absorption bandwidth.

Designing a Carbon Nanotube Field-Effect Transistor with High Transition Frequency for Ultra-Wideband Application

Theoretical calculations predict transition frequencies in the terahertz range for the field-effect transistors based on carbon nanotubes, and this shows their suitability for being used in high frequency applications. In this paper, we have designed a field-effect transistor based on carbon nanotube with high transition frequency suitable for ultra-wide band applications. We did this by optimizing nanotube diameter, gate insulator thickness and dielectric constant. As a result, we achieved the transition frequency about 7.45 THz. The environment of open source software FETToy is used to simulate the device. Also a suitable model for calculating the transition frequency is presented.

Evaluation of System Performance of Ultra-Wide Band Jointing in MC Signaling in Correlated Environments

The evaluation of System Performance of UWB (ultra-wide band) jointing in MC (multi-carrier) signaling in correlated environments is presented in the report. The correlated Nakagami-m statistical distribution for the multipath fading model is assumed in this scenario. In fact to establish the model for analyzing in this article is using MC-CDMA (multi-carrier code-division multiple-access) system characterization combined with a UWB scheme. The average BER (bit error rate) is calculated and compared to a special case of previously published results. Studied results from this paper can be implied to approve the system performance for a UWB system combined with a MC-CDMA wireless communication system. It is worth noting that the Nakagami-m distributed fading parameter significantly dominates UWB system performance when it cooperates with MC signaling under a fading environment. Finally, it is worthy of noting that when the SNR (signal-to-noise ratio) at system’s receiver reaches a preset high threshold value, the parameter of power decay ratio effect could be not included.

Numerical simulation of the coupling of ultra-wide band electromagnetic pulse into landmine by aperture

The modern landmine＇s electronic fuse is susceptible to strong interference or can even be damaged by the ultra-wide band electromagnetic pulse（UWB-EMP）. The finite-difference time-domain（FDTD） method in lossy media with cylindrical coordinates is used to study the interactions of the UWB-EMP with the landmine. First, the coupling of UWB-EMP into the landmine shielding shell through an aperture is numerically simulated. Second, the coupled electromagnetic field of mine shells made of different shielding materials and with apertures of different sizes is plotted. Third, the aperture coupling laws of UWB-EMP into shells are analyzed and categorized. Such an algorithm is capable of effectively preventing ladder similar errors, and consequently improving the calculation precision, and in addition to adopting the message passing interface（MPI） parallel method to divide the total calculating range into more sub-ranges, the overall calculating efficiency is greatly increased. These calculations are surely a constructive reference for modern landmine design against electromagnetic damage.

A Novel Polymorphic Topology with Hybrid Control Strategy Based LLC Resonant Converter for Ultra-Wide Input Voltage Range Applications

To realize effective utilization of renewable energy sources,a novel polymorphic topology with hybrid control strategy based LLC resonant converter was analyzed and designed in this paper.By combining the merits of a full bridge LLC resonant converter,three-level half bridge LLC resonant converter,and variable frequency control mode,the converter realizes an intelligent estimation of input voltage by automatically changing its internal cir-cuit topology.Under this control strategy,different input voltages determine different operation modes.This is achieved in full bridge LLC mode when the input voltage is low.If the input voltage rises to a certain level,it operates in three-level half bridge LLC mode.These switches are digital and entirely carried out by the DSP(Digi-tal Signal Processor),which means that an auxiliary circuit is unnecessary,where a simple strategy of software modification can be utilized.Experimental results of a 500W prototype with 100V~600V input voltage and full load efficiency of up to 92%are developed to verify feasibility and practicability.This type of converter is suitable for applications with an ultra-wide input voltage range,such as wind turbines,photovoltaic generators,bioenergy,and other renewable energy sources.