An organic metamaterial absorber (OMA) with a total thickness of 2.98 mm composed by multi-layer flexible frequency selective surface (FSS) and worked in ultra wideband (UWB) is investigated. The proposed absorber is stacked on a metal substrate by organic materials layer by layer, such as polyimide and polyvinyl chloride. According to equivalent circuit and electromagnetic field analysis, periodic FSS patterns are printed on organic materials using organic conductive ink. The absorption rate of the structure is high up to 90 % and the fractional bandwidth (FBW) reached 147.7 % at 11.78-78.32 GHz, which shows incident angle insensitive within 50(degrees). In addition, the fabricated prototype with a single unit cell of 0.17 g is measured in an anechoic chamber using free space method. Furthermore, the measurement is in great agreement with the simulation, which demonstrates the reliability and the practical application prospect of the provided OMA with flexible, lightweight and ultrathin construction.

A flexible extra broadband metamaterial absorber(MMA)stacked with five layers working at 2 GHz-40 GHz is in-vestigated.Each layer is composed of polyvinyl chloride(PVC),polyimide(PI),and a frequency selective surface(FSS),which is printed on PI using conductive ink.To investigate this absorber,both one-dimensional analogous circuit analy-sis and three-dimensional full-wave simulation based on a physical model are provided.Various crucial electromagnetic properties,such as absorption,effective impedance,complex permittivity and permeability,electric current distribution and magnetic field distribution at resonant peak points,are studied in detail.Analysis shows that the working frequency of this absorber covers entire S,C,X,Ku,K and Ka bands with a minimum thickness of 0.098λmax(λmax is the maximum wave-length in the absorption band),and the fractional bandwidth(FBW)reaches 181.1％.Moreover,the reflection coefficient is less than-10 dB at 1.998 GHz-40.056 GHz at normal incidence,and the absorptivity of the plane wave is greater than 80％when the incident angle is smaller than 50°.Furthermore,the proposed absorber is experimentally validated,and the experimental results show good agreement with the simulation results,which demonstrates the potential applicability of this absorber at 2 GHz-40 GHz.

In this letter, planar type self-powered short-wavelength infrared narrowband Si photodetector was realized based on a simple Schottky structure by increasing surface states and enlarging the distance between Schottky electrode and light irradiation region. With the assistance of pyramid microstructure, the distance needed for sub-100 nm narrowband detection effectively decreased from $1000~\mu \text{m}$ to $200~\mu \text{m}$ , which is vital to improving device sensitivity and reducing device size. The obtained photodetector exhibited a response peak at 1119 nm with full-width at half-maximum of 97 nm. At zero bias, a peak detectivity up to ${2}.{25}\times {10} ^{{11}}$ Jones, linear dynamic range of 91 dB and fast response speed (Rise time of $88~\mu \text{s}$ and fall time of $118~\mu \text{s}$ ) were achieved. The higher wavelength selectivity and sensitivity than its counterpart with flat surface should be ascribed to the large number of surface state and pronounced light confinement effect of pyramid microstructure. This work opens up a new avenue for achieving planar-type narrowband photodetector that can provide better integration capabilities for on-chip applications than vertical devices.

The development of high-performance multispectral photodetector with narrowband and tunable spectral sensitivity is of importance but remains highly challenging to date. Here, we have reported on the fabrication of a Si Au/n-type Si/Au photodetector with tunable narrowband sensitivity not only in ultraviolet but also in near-infrared region, which is related to the controlled charge collection narrowing (CCN) mechanism. What is more, the negative response peak of the device can be readily tuned from 365 to 605 nm, and the positive response peak can be modulated from 938 to 970 nm when the bias varies from 0.1 to −0.1 V. In particular, the full-width at half-maximum is as small as 92 and 117 nm when the negative and positive response peaks approach the ultraviolet short wavelength end and near-infrared long wavelength end, respectively. The opposite polarity of the device responses in ultraviolet-visible and near-infrared regions renders the present Si photodetector potentially important in future multiple band optoelectronic systems.

An ultra-wideband metamaterial absorber (MA) consisting of three layers of resistive ink separated by two layers of polymethacrylimide is proposed. The results of full-wave simulation show that the absorptivity is high up to 95% with a bandwidth ratio of 1:9.73 over the wide frequency range from 4.20 to 40.87 GHz, covering the whole C, X, Ku, K, and Ka bands. Moreover, the MA is insensitive to polarization and exhibits wide-angle stability, which is investigated by the full-wave simulation results as well as the analysis of multi-reflection interference theory. The fabricated prototype with a single unit cell of 0.081 g is tested using free-space measurement in an anechoic chamber, and the measured results are in good agreement with the simulation results, which prove the robustness of the design and indicates a practical application prospect of the proposed ultra-wideband MA with lightweight, simple, and compact structure.

For potential military applications, a flexible metamaterial absorber (MMA) working on whole K-bands with total-thickness of 3.367 mm, ultra-broadband, polarization-insensitive, and wide-angle stability is presented based on frequency-selective surface (FSS). The absorber is composed of polyvinyl chloride (PVC) layer, polyimide (PI) layer, and poly tetra fluoro ethylene (PTFE) layer, with a sandwich structure of PVC–PI–PTFE–metal plate. Periodic conductive patterns play a crucial role in the absorber, and in traditional, it is designed on the upper surface of PI layer to form LC resonance. Different from commonly absorber, all the patterns are located on the lower surface of the PI layer in this work, and hence the impedance matching and absorptivity are improved in this purposed absorber. The flexible absorber with patterns on lower surface of the PI layer is compared with that on upper surface of the PI layer, the difference and the reasons are explained by absorption mechanism based on equivalent circuit model, and surface current density and electric field distribution are used to analyze resonance peaks. Absorptivity is greater than 90% in a frequency range of 10.47 GHz–45.44 GHz with relative bandwidth of 125.1%, covering the whole Ku, K, Ka, and some of X, U bands, especially containing the whole K bands from 12 GHz to 40 GHz. Radar cross section (RCS) is reduced at least 10 dB in 11.48 GHz–43.87 GHz frequency ranges, and absorption remained about 90% when the incident angle changed from 0 ° to 55°. The purposed absorber is fabricated, measured, and experiment results show good agreement with theoretical analysis and numerical simulation. After bonded on outer surface of different cylinders with diameters of 200 mm and 100 mm, the absorption of MMA is approximately reduced 10% and 20% respectively, which shows good conformal character with surface of various curvatures. Due to the attractive performance on strong absorption in the whole K-bands, flexible and easy conformal, our design exhibits broad potential application in radar stealth and sensors.

目前有关中文BCI输入系统的研究仅有拼音输入和笔画输入两种,且都克服不了中文输入速率较低、不便携等问题.据此提出了基于P300的五笔中文输入系统.此系统通过低成本OpenBCI套件,使用Wi-Fi协议传输脑电数据,在移动设备上实现刺激界面,并使用卷积神经网络处理脑电信号.实验表明,该系统具有高中文输入速率、高准确率以及便携化等特点.

偏心介质柱的电磁散射是电磁探测过程中经常碰见的问题,传统上采用数值方法进行求解,为此,求取了其在线电流源激励下的解析解.通过采用模式匹配法,将模型的边界条件转化为矩阵方程,再由矩阵方程进一步得到偏心介质柱的电磁散射解析解.该解在实际模型计算中速度快,较传统方法提高了求解效率.通过与有限差分法得到的数值结果对比,得到的解析解与数值解高度一致,较前人文献结果更准确.该解析解不仅可用于线电流源激励下偏心介质柱电磁散射的快速计算,对半空间内柱状物体的电磁散射特性研究也有重要意义.

The poling conditions of the 6.5MHz PbZrO3-PbTiO3 (PZT) piezoelectric ceramic filters have been studied. A new poling technology, which is two poling processes before and after ceramic disks are respectively coated with silver film electrode, is introduced. The optimal poling conditions are described. The effects of two poling process are good for the electrical properties and mechanical performance compared with the previous poling. The experimental results are analyzed based on energy-trap phenomenon and the forming of domain. The two poling technology is also useful for the preparation of other piezoelectric ceramic components and devices

分析了微带不连续性辐射的基本原理,采用FDTD方法和坡印廷矢量法相结合,研究了拐角、短截线等微带不连续性的辐射特性,对微带不连续性和微带贴片天线的辐射机理进行了比较.仿真结果显示,不连续性表面波和空间波辐射损耗随着频率的增加而显著增大,低频时辐射损耗以空间波辐射为主,高频时表面波辐射有超过空间波的趋势.微带短截线的谐振辐射特性与矩形微带贴片天线类似,只是在辐射强度上有较大的差别.

集成电路版图设计涵盖了微电子学、电路理论、计算机图形学等诸多学科的基础理论,这是微电子学专业的办学重要特色和人才培养重点方向。以CMOS反相器和基本MOS差分放大器为例,介绍了集成电路版图设计的教学内容。学生通过集成电路版图设计的教学环节,巩固了专业课程的理论知识,提高了集成电路设计的实践能力。

Based on electromagnetic simulation software,using finite difference of time domain,a series of simulation experiments of antennas are designed.The antennas is modeled and simulated by the simulation software,and a series of antenna performance parameters are obtained by computing,such as far field radiation pattern,reflection loss,voltage standing wave ratio,impedance matching,etc.Far field radiation characteristics of rectangle patch antenna,linear antenna array,phased array antenna and planar antenna array are calculated and discussed,then the feasibility of simulation experiments for Antenna course is verified in teaching.Practice proves that the simulation experimental teaching is a useful means to improve teaching effect of Antenna course.

The effect of the microstrip bend on the propagation characteristics of a microstrip line was investigated based on the Finite-Difference Time-Domain（FDTD）method.The dispersive characteristics of a microstrip line with a bend are quite different from that of a uniform straight microstrip line.The effect of bend discontinuity on propagation constants deceases exponentially with the distance form the corner of the bend.This can be explained by the fact that the higher order modes excited by the bend discontinuities have intrinsic properties of exponentially decay with the distance from the bend discontinuities.This effect can be negligible（less than five percent）when the distance is beyond ten times of conductor strip width.The S parameters and propagation constants comparison between unmitered and mitered bends are also presented.The proposed method which takes advantage of the FDTD algorithm and the Root Mean Square Deviation（RMSD）analysis is also an effective way for analyzing the dispersion characteristics of other planar transmission lines.

Based on a microstrip antenna that working on 1.79 GHz,this paper firstly presents the design technique for phase shifter,and then different phased array antennas is designed by two kinds of phase shifter.Using FDTD to model and simulate it,the far field radiation patterns of arrays is calculated,and then the deviation between experiment and theory is analyzed.The phased array antennas are designed by single structure with narrow main lobe,which maximum scan angle is larger than 45°.

The algorithm realisation and main functions of 3D full-wave electromagnetic analysis software are addressed.The software consists of two main modules:the electromagnetic modelling and the FDTD numerical solver,it can be used in electromagnetic field analysis and design for systems of radio frequency and microwave,etc.The software conducts uniform and non-uniform mesh generation automatically in accord with FDTD algorithm conditions,forms data files needed by describing media,mesh,boundary condition,stimulus source setting,etc.It is convenient to observe and modify the targeted objective timely by translating,rotating and scaling operations,has quite high electromagnetic modelling efficiency and 3D visualised effect,which implements the dynamic variation demonstration of electromagnetic field in computation interval.The functions and applied value of the software have been verified through practical project application as well as the comparison with commercial software HFSS.

In this paper, different approaches to calculate the characteristic impedance of slotlines by finite difference time domain (FDTD) method is presented. It shows that for non-TEM mode transmission lines, different definitions of Z0 yield completely different results. Then a more rational definition of characteristic impedance of slotlines is proposed. Result is obtained and compared with other definitions.

The characteristics of the typical microstrip discontinuities, such as right-angle bends, T junctions and steps in width, are investigated based on the Finite-Difference Time-Domain (FDTD) method in a wide-frequency range. The compensation methods of the microstrip discontinuities are also discussed and compensated discontinuities can improve the circuit performance as well as the bandwidth compared with the uncompensated. The electric field varying with signal traveling in the spatial and time domain at the microstrip discontinuities are also presented.

The mechanism of sidegating effect hysteresis in GaAs MESFETs is analyzed in this paper.The analysis shows that the sidegating effect hysteresis in GaAs MESFETs is associated with both electronic properties of the channel-substrate interface region and deep level electron traps in semi-insulating GaAs substrates.The analysis result can well explain the experimental results.In addition,the analysis result is useful for understanding other properties of GaAs devices.

LAN visual telephone(conference) system based on Java has features such as cross-platform.Multi-channel application of JMF data source is a crucial part of the system.A solution to implement multi-channel application of JMF data source is presented.The proposed scheme can be used to realize synchronously native playing,multi-channel transmitting on LAN and native monitoring.This solution puts emphasis on the technology of cloning data source and configuring the ports of multi-channel transmision,which is simple,stable and practicable for developing LAN visual telephone(conference) based on JMF.

The polarization technology of the 6.5 MHz PZT piezoelectric ceramic filter is introduced.The polarization electric field,polarization temperature and polarization time are studied based on experiments.Theoretical analysis is presented according to the experimental results.The proper polarization electric field,polarization temperature and polarization time are 2.2 kV/mm,130 ℃ and 15 min respectively.Other problems of polarization technology are also discussed.Thus the piezoelectric property of piezoelectric ceramic is improved effectively.