单元方向图对阵列综合性能影响分析

在阵列天线综合问题中,传统方法假设各辐射单元各向同性且忽略互耦效应。工程应用中这些忽略会给计算结果带来较大的误差。本文首先建立了天线单元方向图对天线阵列性能影响的数学模型,对阵列指向精度、目标方向图赋形等问题进行了仿真对比分析。为了克服由单元方向图带来的误差,将阵中单元方向图代入优化过程中,算例表明该措施的有效性。考虑了阵列边缘单元辐射特性差异对阵列性能的影响。仿真结果表明在优化过程中考虑这些差异可以进一步提高计算精度。     

Anodic-Oxidation Growth of Microscopic Pillar Arrays: Kinetic Aspects

The three-step fabrication of microscopic pillar arrays by the anodic oxidation of Al/Ta thin-film structures on dielectric or silicon substrates is studied experimentally. The major features of pillar-growth kinetics are described. The main properties of the arrays are evaluated by scanning electron microscopy and simultaneous current–voltage tracing. The ranges of variation for geometric array parameters are determined. The pillars grown have a maximum height-to-diameter ratio of 17.0, a maximum height of 540 nm, and a minimum radius of about 15 nm. The maximum density of pillars in an array is 8.25 × 10¹⁰cm^–2. A good reproducibility of physical and morphological properties is achieved for large-area pillar arrays. Potential applications of pillar arrays are recited: light-emitting diodes, thin-film controllers, solar batteries, spatial light modulators, polarizers, etc. It is noted that an investigation into the fabrication of pillar arrays for field-emitter displays is currently in progress.     

New 5.8-GHz circularly polarized retrodirective rectenna arrays for wireless power transmission

This paper proposes two new circularly polarized retrodirective rectenna arrays, including a 2 /spl times/ 2 array and a 4 /spl times/ 4 array. A proximity-coupled microstrip ring antenna is used as the retrodirective rectenna array element, which can automatically block harmonic signals up to the third order from reradiating by the rectifying circuit. These arrays are printed on a Rogers Duroid 5880 substrate of /spl epsiv//sub r/=2.2 with a two-layer structure, with a total thickness of 1.5748 mm (or 62 mil). The new retrodirective rectenna array can track the incoming power source signals automatically and is less sensitive to the power incident angle variations, i.e., main-beam alignment deviation. It can provide a nearly constant dc output voltage within /spl plusmn/10/spl deg/ and 90% dc output voltage within /spl plusmn/45/spl deg/. The conversion efficiencies of the two arrays are 73.3% and 55%, respectively, when the power density is 10 mW/cm/sup 2/. The retrodirective rectenna array can be used in the low-power density applications for microwave wireless power transmissions.     

Hierarchical interconnection structures for field programmable gatearrays

Field programmable gate arrays (FPGA's) suffer from lower density and lower performance than conventional gate arrays. Hierarchical interconnection structures for field programmable gate arrays are proposed. They help overcome these problems. Logic blocks in a field programmable gate array are grouped into clusters. Clusters are then recursively grouped together. To obtain the optimal hierarchical structure with high performance and high density, various hierarchical structures with the same routability are discussed. The field programmable gate arrays with new architecture can be efficiently configured with existing computer aided design algorithms. The k-way min-cut algorithm is applicable to the placement step in the implementation. Global routing paths in a field programmable gate array can be obtained easily. The placement and global routing steps can be performed simultaneously. Experiments on benchmark circuits show that density and performance are significantly improved     

Nanoneedle Platforms: The Many Ways to Pierce the Cell Membrane

Establishing techniques to efficiently and nondestructively access the intracellular milieu is essential for many biomedical and scientific applications, ranging from drug delivery, to electrical recording, to biochemical detection. Cell penetration using nanoneedle arrays is currently a research focus area because it not only meets the increasing therapeutic demands of cell modifications and genome editing, but also provides an ideal platform for tracking long‐term intracellular information. Although the precise mechanism driving membrane penetration by nanoneedle arrays is still unclear, the low cytotoxicity, wide range of delivered materials, diverse cell type targets, and simple material structures of nanoneedle arrays make these splendid platforms for cell access. Here, the recent progress in this field is reviewed by examining device architectures and discussing mechanisms for nanoneedle penetration, and the major studies demonstrating the most general applicability of nanoneedle arrays, typical methodologies to access the intracellular environment using nanoneedles with spontaneous or assisted penetration modes, as well as biosafety aspects are presented. This review should be valuable for deeply understanding the materials fabrication principles, device designs, cell penetration methodologies, biosafety aspects, and application strategies of nanoneedle array‐based systems that are of crucial importance for the development of future practical biomedical platforms.     

Rate equations analysis of phase-locked semiconductor laser arrays under steady state conditions

Rate equations analysis of phase-locked semiconductor laser arrays has been carried out. It was found that for given (Laser) current densities, the photon density distribution in the array elements is that particular one which maximizes the total photon density. The results of this analysis were then combined with the waveguiding properties of the laser array waveguide, yielding a basic model of phase-locked diode laser arrays. This model explains the effects of the variation of the current combination through the array elements on its mode structure that were observed recently.     

Transparent metal oxide electrode CID imager

The use of metal oxide transparent conductive electrodes in a charge-injection device (CID) imaging array has resulted in a quantum efficiency of approximately 70 percent, uniform throughout the visible, with useful array response out to 3500 /spl Aring/. The advantages of using highly transparent metal oxide electrodes for the fabrication of frontside illuminated arrays is described. A new high density CID cell is described, which does not require any contact windows or diffused regions. This cell structure is simply composed of two crossed rows and column electrodes and is easily fabricated. Because no contacts are required, it can be reduced in size for large high density arrays. The results for a 32/spl times/32 self-scanned array are presented.     

Transparent metal oxide electrode CID imager

The use of metal oxide transparent conductive electrodes in a charge-injection device (CID) imaging array has resulted in a quantum efficiency of approximately 70 percent, uniform throughout the visible, with useful array response out to 3500 Å. The advantages of using highly transparent metal oxide electrodes for the fabrication of frontside illuminated arrays is described. A new high density CID cell is described, which does not require any contact windows or diffused regions. This cell structure is simply composed of two crossed rows and column electrodes and is easily fabricated. Because no contacts are required, it can be reduced in size for large high density arrays. The results for a 32 × 32 self-scanned array are presented.     

Using Stacked Bitlines and Hybrid ROM Cells to Form ROM and SRAM-ROM With Increased Storage Density

ROM cell architectures are proposed that have roughly 20% greater storage density in the cell array compared to that of a conventional ROM. Increased density is achieved by exploiting the multiple interconnect layers now available in common logic processes and by using multiple ROM cell types in combination. The storage density of arrays of these hybrid ROM cells increases further as more interconnect layers become available. In addition, a new SRAM-ROM architecture is presented that capitalizes on these techniques to add ROM capability to a conventional SRAM cell with no additional transistors in the memory cell and little or, in some cases, no impact on the cell area     

The bi-polar near-field antenna measuring system at Wroclaw University of Technology

This paper presents a near-field antenna measurement system that was developed in-house. The capabilities of our bi-polar system were extended by a backward-projection processing of data. The amplitude and phase distribution within the array elements can thus be reconstructed. Major applications of the presented near-field system are in research on advanced beamforming, and in investigations into large-scale integration of lightweight arrays. The results presented were obtained for planar microstrip arrays, and for a phased array operating between 5 GHz and 12 GHz.     

Phased array theory and technology

This review of array antennas highlights those elements of theory and hardware that are a part of the present rapid technological growth. The growth and change in array antennas include increased emphasis on "special-purpose" array techniques such as conformal and printed circuit arrays, wide angle scanning arrays, techniques for limited sector coverage, and antennas with dramatically increased pattern control features such as low sidelobe, adaptively controlled patterns. These new topics have substantially replaced large radar arrays in the literature and constitute a major change in the technology. The paper presents a tutorial review of theoretical developments emphasizing techniques appropriate to finite arrays, but indicating parallel developments in infinite array theory, which has become the useful tool for analysis of large arrays. A brief review of the theory of ideal arrays is followed by a generalized formulation of array theory including mutual coupling effects, and is appropriate to finite or infinite arrays of arbitrary wire elements or apertures in the presence of a conducting ground screen. Some results of array tolerance theory are summarized from the literature and retained as reference throughout discussions of array component requirements and device tolerance for low sidelobe arrays. Examples from present technology include conformal and hemispherical coverage arrays, lightweight printed circuit arrays, systems for use with reflectors and lenses in limited sector coverage applications, and wide-band array techniques.     

An External Calibration Scheme for DBF Antenna Arrays

A novel calibration scheme is presented that is especially suited for complex digital beamforming (DBF) antenna arrays at millimeter-wave frequencies. Calibration data is extracted by sampling the field of each radiator at certain locations near the array by fixed probe antennas. A scalable calibration model for evaluation of the measured data is described. First tests are performed on a small passive array representing a unit cell of larger arrays. The calibration scheme is subsequently applied to and tested on a 64 element DBF transmit antenna array.      

User-programmable gate arrays

A very flexible gate array that speeds the job of designing, updating, or varying the logic circuitry that turns standard microprocessor and memory ICs into computers and peripheral equipment is examined. The gates on this kind of IC are interconnected under software control, and downloaded into local memory cells from a program written by the user, which can alter it almost at will. The array is manufactured with a grid of interconnections consisting of metal segments and programmable switching points. The user's program defines which switching points are on and which are off, and in this way groups and interconnects the gates into useful functions. On conventional gate-array ICs, the interconnections are made once and for all by the manufacturer using photolithographic masks. Various types of arrays and methods for programming them are described. The approach to designing them is discussed, highlighting differences from the process for factory-configured gate arrays. Some example applications are presented     

The tapered slot antenna-a new integrated element formillimeter-wave applications

Tapered slot antennas (TSAs) with a number of potential applications as single elements and focal plane arrays are discussed. TSAs are fabricated with photolithographic techniques and integrated in either hybrid or MMIC circuits with receiver or transmitter components. They offer considerably narrower beams than other integrated antenna elements and have high aperture efficiency and packing density as array elements. Both the circuit and radiation properties of TSAs are reviewed. Topics covered include: antenna beamwidth, directivity, and gain of single-element TSAs; their beam shape and the effect of different taper shapes; and the input impedance and the effects of using thick dielectrics. These characteristics are also given for TSA arrays as are the circuit properties of the array elements. Different array structures and their applications are also described     

Fabrication of Multifaceted Micropatterned Surfaces with Laser Scanning Lithography

The implementation of engineered surfaces presenting micrometer‐sized patterns of cell adhesive ligands against a biologically inert background has led to numerous discoveries in fundamental cell biology. While existing surface patterning strategies allow patterning of a single ligand, it is still challenging to fabricate surfaces displaying multiple patterned ligands. To address this issue we implemented laser scanning lithography (LSL), a laser‐based thermal desorption technique, to fabricate multifaceted, micropatterned surfaces that display independent arrays of subcellular‐sized patterns of multiple adhesive ligands with each ligand confined to its own array. We demonstrate that LSL is a highly versatile “maskless” surface patterning strategy that provides the ability to create patterns with features ranging from 460 nm to 100 μm, topography ranging from ‐1 to 17 nm, and to fabricate both stepwise and smooth ligand surface density gradients. As validation for their use in cell studies, surfaces presenting orthogonally interwoven arrays of 1 μm × 8 μm elliptical patterns of Gly‐Arg‐Gly‐Asp‐terminated alkanethiol self‐assembled monolayers and human plasma fibronectin are produced. Human umbilical vein endothelial cells cultured on these multifaceted surfaces form adhesion sites to both ligands simultaneously and utilize both ligands for lamella formation during migration. The ability to create multifaceted, patterned surfaces with tight control over pattern size, spacing, and topography provides a platform to simultaneously investigate the complex interactions of extracellular matrix geometry, biochemistry, and topography on cell adhesion and downstream cell behavior.     

纳米结构在太阳电池中的应用

太阳电池是新能源领域一个不可忽视的领域。随着纳米技术的不断发展,纳米技术和太阳电池有了越来越多的结合点。综述了纳米结构阵列在太阳电池中的应用,其中包括光子晶体、纳米棒阵列、纳米孔阵列、纳米光栅、屋顶状阵列等纳米结构在太阳电池的活性层、减反层以及电极层中的应用。通过提高光吸收、增大p-n结界面比例、提高载流子传输效率等机理提高太阳电池能量转换效率,揭示了纳米结构在降低太阳电池成本、提高太阳电池能量转换效率方面存在的巨大应用潜力。     

Conical array studies

Present requirements for wide-band spread-spectrum techniques for many applications offer attractive potential uses for circular symmetric arrays. Since rigorous analytical techniques are not available to investigate conical array characteristics, experimental techniques can be used to simulate scanning of the conical array. This paper describes techniques that give some insight into the behavior of conical arrays of dipoles. A projected distribution is used to simulate array properties such as beamwidth, sidelobe level, and polarization. Comparisons with a similar cylindrical array are made. Element patterns are examined to determine if behavior is similar to known behavior of element patterns for the cylindrical array. Finally, a conical sector experimental array is used to simulate selected "scanned" beam positions to determine array behavior, i.e., beamwidth, scan limits, polarization, and sidelobe level. Experimental and calculated array patterns, element patterns, and polarization data are given.     

Microwave modeling of 2-D active grid antenna arrays

A new measurement technique for determining the broadband driving point impedance of large two-dimensional active grid arrays is presented. The active array radiates a plane wave in the broadside direction when all elements are locked in phase. For analysis, the array is reduced to a single unit cell by exploiting the array symmetries. The driving point impedance of the unit cell is determined by using the dielectric waveguide measurement method (DWM). The approximations of the method are discussed, and the method is compared with other measurement techniques. Results are presented for four square arrays: dipole, bow-tie, double-vee and slot array. The measurement method is verified by comparing it to the full-wave theory in the whole range. It is shown that all four antenna arrays can be represented by very simple circuits that use only transmission lines as circuit elements. The bow-tie array is found to represent the best choice for broadband operation     

Phased arrays based on oscillators coupled on triangular and hexagonal lattices

Phased arrays have been proposed in which a two-dimensional array of voltage-controlled oscillators coupled to nearest neighbors provides excitations for the radiating elements which are properly phased to result in a steerable radiated beam. These arrays have been arranged on a rectangular lattice and the beam is steered by tuning the oscillators along the four edges of the array. Proposed here are similar arrays in which the oscillators are coupled on a triangular lattice or a hexagonal lattice and provide excitations for radiating elements similarly disposed in a planar triangular array. Beam steering is accomplished by tuning the oscillators along the three edges of the array. The dynamic behavior of the arrays is studied via a continuum model and the results compared with those of a full nonlinear discrete analysis and a linearized discrete model.     

锌衬底上直接生长密度可调的氧化锌纳米棒阵列和场发射特性

在锌衬底上制备了取向生长、形貌各异、不同密度的氧化锌纳米棒阵列.研究发现,氧化锌纳米棒在温度低于70℃、适量的碱性溶液、大气压下能够在锌衬底上大规模制备,并且氧化锌纳米棒的直径,在锌衬底上的密度和形貌完全依赖于氢氧化钠和硝酸锌的浓度.场发射测试表明:氧化锌纳米棒阵列开启电场较低(电流密度达1μA/cm2时场强仅为3.8 V/μm),显示了氧化锌纳米棒阵列在场发射方面的潜在应用.