Multilevel Surface Decomposition Algorithm for Rapid Evaluation of Transient Near-Field to Far-Field Transforms

A fast multilevel algorithm with reduced memory requirements for the evaluation of transient near-field to far-field transforms is presented. The computational scheme is based on a hierarchical decomposition of an arbitrary shaped enclosing surface over which the near-fields of an antenna or a scatterer are given. For surface subdomains at the highest decomposition level, the angular-temporal far-field patterns are calculated directly from the known near fields over a sparse angular grid of directions and a short temporal duration. The multilevel computation comprises angular and temporal interpolations thus increasing angular resolution and temporal duration of radiation patterns while aggregating the subdomain contributions between successive decomposition levels. These steps are repeated until obtaining the transient far-field response of the whole enclosing surface. The computational complexity of the proposed algorithm is substantially lower than that of the direct evaluation. Reduction in memory requirements is obtained by formulating the algorithm as a marching-on-in-time windowed scheme. This approach allows for embedding of the accelerated transforms within existing near-field modeling tools.      

Passive Localization of Mixed Near-Field and Far-Field Sources Using Two-stage MUSIC Algorithm

Passive source localization is one of the issues in array signal processing fields. In some practical applications, the signals received by an array are the mixture of near-field and far-field sources, such as speaker localization using microphone arrays and guidance (homing) systems. To localize mixed near-field and far-field sources, this paper develops a two-stage MUSIC algorithm using cumulant. The key points of this paper are: (i) in the first stage, this paper derives one special cumulant matrix, in which the virtual ?steering vector? is the function of the common electric angle in both near-field and far-field signal models so that source direction-of-arrival (DOA) (near-field or far-field one) can be obtained from this electric angle using the conventional high-resolution MUSIC algorithm; (ii) in the second stage, this paper derives another particular cumulant matrix, in which the virtual ?steering matrix? has full column rank no matter whether the received signals are multiple near-field sources or multiple far-field ones or their mixture. What is more important, the virtual ?steering vector? can be separated into two parts, in which the first one is the function of the common electric angle in both signal models, whereas the second part is the function of the electric angle that exists only in near-field signal model. Furthermore, by substituting the common electric angle estimated in the first stage into one special Hermitian matrix formed from another MUSIC spectral function, the range of near-field sources can be obtained from the eigenvector of the Hermitian matrix. The resultant algorithm avoids two- dimensional search and pairing parameters; in addition, it avoids the estimation failure problem and alleviates aperture loss. Simulation results are presented to validate the performance of the proposed method.     

Analysis of High-Performance Flip-Flops for Submicron Mixed-Signal Applications

This paper presents a detailed analysis of high-performance edge-triggered memory elements for deep submicron mixed-signal applications. The variations of the main parameters (power, delay, peak of supply current) with supply voltage, as well as timing restrictions have been studied. Especial emphasis has been given to switching-noise generation, an aspect of important concern in mixed-signal applications. We have analyzed the sources of switching noise, noticing that, the less noisy flip-flops are those based on differential structures.     

基于局域共振机制的平面型金属-电介质电磁波带隙结构的实验研究

研究了具有高阻抗的电磁带隙(EBG)的双层平面型金属-电介质周期性单元结构,此类结构的特定频率的表面波抑制和同相位反射性质在微波天线及高速电路中有广阔应用前景。本文根据S ivenp iper等效电路模型,初步分析了表面波带隙与EBG单元结构的几何参数的关系,然后通过实验研究了TM表面电磁波高阻抗电磁表面的表面波带隙的参数特征。论证了关于EBG高阻抗电磁表面的几何参数(单元长度、单元间距、介质厚度、导孔直径)、方向性以及周期数(单元数)对其表面波带隙特征的影响,并对此作了讨论分析,所得结论为高阻抗电磁表面的设计提供了依据。     

An Electromagnetic Near-Field Sensor for Simultaneous Electric and Magnetic-Field Measurements

This paper describes the theory of a single sensor to perform simultaneous electric and magnetic near-field measurements. The theory indicates that it is possible to measure the magnetic-loop and electricdipole currents using a loop antenna terminated with identical loads at two diametrically opposite points. The theory also indicates that it is possible to choose an ideal load impedance for achieving equal electric and magnetic-field responses of the loop. Preliminary experiments have been performed using a plane-wave field to verify these results.     

A Double-Surface Electromagnetic Bandgap Structure With One Surface Embedded in Power Plane for Ultra-Wideband SSN Suppression

In this letter, a double-surface electromagnetic bandgap (EBG) structure with one EBG surface embedded in power plane is proposed for ultra-wideband simultaneous switching noise (SSN) suppression in printed circuit boards. The SSN suppression bandwidth is broadened to wider than 30 GHz with a low start frequency by combining traditional EBG structure and the coplanar EBG structure which is embedded in the power plane. Because the coplanar EBG surface is embedded in the power plane, no additional metal layer is introduced by the double-surface EBG structure. Simulations and measurements are performed to verify the broadband SSN suppression, high performance is observed.     

Study on the Microwave Transmission Characteristics of a Three-Dimensional Electromagnetic Bandgap Structure with Coupled Defects

The influence of a vertical coupled defect on the localized properties of a diamond electromagnetic bandgap (EBG) structure has been studied in the present research. The diamond EBG structure with a cavity defect was fabricated by stereolithography and gel-casting processes with alumina slurry. The resonant peaks of two kinds of defects were compared by measuring their microwave transmission characteristics using a network analyzer. A higher quality factor (Q) was obtained for the diamond EBG structure with a vertical coupled defect, and the transmission efficiency of resonant peak was improved by 29.6% in comparison with a single defect. Experimental results agreed with the simulation results. These microwave transmission characteristics of the three-dimensional (3D) EBG structures indicate that they can be applied in microwave devices to improve transmission efficiency.     

Review of Near-Field Terahertz Measurement Methods and Their Applications

In the last decades, many research teams working at Terahertz frequencies focused their efforts on surpassing the diffraction limit. Numerous techniques have been investigated, combining methods existing at optic wavelength with THz system such as Time Domain Spectroscopy. The actual development led on one side to a resolution as high as ??/3000 and one the other side to a video-rate recording. The purpose of this paper is to give an overview of the history of the field, to describe the different approaches, to give examples of existing applications and to draw the perspective for this research area.     

基于局部散射中心的近、远场微动回波时频分布特性的解析表达

微多普勒效应是由目标(或其部件)的转动、振动、进动等微动引起的频率调制现象,能够反映目标的几何结构和运动状态。该文全面分析了近、远场探测条件下目标扇叶转动引起的微动回波的时频分布特性。首先建立了近、远场雷达微动回波模型。然后从远场微动回波模型中推导其瞬时频率表达式,结果表明远场微动回波的时频图中包含由叶尖散射点、叶彀散射点和镜面反射点引入的正弦型flash、零频flash和矩形flash。最后,在近场条件下,直接推导得到上述3类局部散射点的瞬时频率表达式,表明近场微动回波时频图呈现类正弦型flash,零频flash和部分余弦型flash的组合。该文还从积分运算性质和电磁散射理论两方面解释了上述flash的形成机理,揭示了它们与扇叶数目、尺寸、转速等参数之间的关系。该文结果将有助于目标精细化建模、分类识别等应用。仿真和实测数据结果均证明了分析结果的正确性。     

Statistical Analysis and Optimization of a Bandgap Reference for VLSI Applications

Voltage and current references are widely needed for all kinds of integrated circuits, as most applications require temperature-independent references with a high reproducibility in mass production. For this purpose normally bandgap references are used. Though it is a common task to set up an application specific bandgap circuit, handling of the statistical design aspects is often not a standardized step in the design flow. This article describes some of the steps that were taken during the design of a bandgap reference for a given VLSI application. All statistical simulations were carried out with the simulation tool GAME (General Analysis of Mismatch Effects) which is used at Infineon/Düsseldorf since 1999.     

HC-PCF的传输特性及其应用

简要介绍了光子晶体的原理,由此引出光子带隙型光子晶体光纤的概念、结构、导光机理及其制备,着重分析空气导光型光子晶体光纤的传输特性,并用时域有限差分(FDTD)法仿真了三角形结构空气导光型光子晶体的色散特性,最后展望其应用前景.     

纳米光存储薄膜结构的光学性质

近场超分辨纳米薄膜结构可以突破衍射极限实现纳米尺寸信息存储,是下一代海量存储技术的重要方案之一,也是纳米光子学研究中的热点.纳米膜层结构基于激光作用下的非线性局域光学效应实现超分辨.分析了超分辨近场薄膜结构突破衍射极限的光学原理,对超分辨纳米薄膜结构的表面等离子体激发特性、非线性光学特性、近场光学特性和超透镜效应等重要光学性质的最新研究进展做了系统介绍.     

改进的物理光学法分析远场目标的电磁散射特性

提出一种改进的物理光学(PO)法来计算远场目标的电磁散射特性.这种方法通过严格的积分变换,经过详细推导,给出了目标单站RCS表达式,可以有效地处理任意外形的纯导体的雷达散射截面计算问题.通过Stokes变换,传统PO表达式中面积分转换为线积分,使得计算效率明显提高.通过一个金属圆形平板和一个金属三角板的算例演示,验证了新方法和PO的精度是相当的.最后,还展示了一个3维的例子.     

A Novel Compact Spiral Electromagnetic Band-Gap (EBG) Structure

A novel compact electromagnetic band-gap (EBG) structure in a spiral shape is presented and investigated. This structure significantly enlarges the capacitance between neighboring elements. The simulations and experimental results have proved that the size of the spiral structure is only 30.9% of the conventional EBG structure. Two applications have been shown, including patch antenna with the spiral EBG structure and a double-element microstrip antenna array with low mutual coupling. The measured results show that a gain improvement over 3 dB and a significant reduction of cross polarization in H-plane are obtained. A 6 dB reduction of mutual coupling is achieved in a double-element EBG microstrip antenna array.     

宽禁带半导体技术最新进展

介绍DARPA宽禁带半导体技术计划第二阶段计划目标及其演示进展情况.     

A S-Bridged Inductive Electromagnetic Bandgap Power Plane for Suppression of Ground Bounce Noise

In this letter, a novel power plane using an inductive S-bridged electromagnetic bandgap (EBG) is proposed for ultra wideband suppression of the ground bounce noise. The S-shaped bridge detouring unit cells effectively increase the power plane inductance. -30 dB stopband is realized from 220 MHz to 7 GHz. The stopband lower limit (220 MHz) of the proposed EBG has been greatly reduced from that (550 MHz) of L-bridged EBG. It is expected that the number of local decoupling capacitors for the power plane integrity is reduced using the proposed S-bridged EBG without the self resonance effect.     

Complex-Point Dipole Formulation of Probe-Corrected Cylindrical and Spherical Near-Field Scanning of Electromagnetic Fields

A probe-corrected electromagnetic theory based on complex-point dipoles is presented for computing the field of an arbitrary source of finite extent (for example a test antenna) from measurements of its near field on a cylindrical or spherical scanning surface. By representing the probe with complex-point dipoles, probe correction is achieved by simple factors that involve Hankel functions evaluated at complex points. Only four complex-point dipoles are needed to represent a typical precision probe used in near-field measurements. The theory uses neither translation and rotation theorems nor differential operators. One disadvantage of the theory is that it employs nonlinear optimization to determine the parameters of the probe model. The complex-point dipole representation of the probe makes realistic simulations of near-field scanning systems straightforward. The cylindrical theory is validated through a numerical example. The spherical theory is validated by experimental data.     

Subthreshold Performance of Dual-Material Gate CMOS Devices and Circuits for Ultralow Power Analog/Mixed-Signal Applications

Analog circuits based on the subthreshold operation of CMOS devices are very attractive for ultralow power, high gain, and moderate frequency applications. In this paper, the analog performance of 100 nm dual-material gate (DMG) CMOS devices in the subthreshold regime of operation is reported for the first time. The analog performance parameters, namely drain-current (I_d), transconductance (g_m), transconductance generation factor (g_m/I_d), early voltage (V_A), output resistance (R_o) and intrinsic gain for the DMG n-MOS devices, and and for the DMG p-MOS devices are systematically investigated with the help of extensive device simulations. The effects of different capacitances on the unity-gain frequency are also studied. The DMG CMOS devices are found to have significantly better performance as compared to their single-material gate (SMG) counterpart. More than 70% improvement in the voltage gain is observed for the CMOS amplifiers when dual-material gates, instead of single-material gates, are used in both the n- and p-channel devices.     

Practical Harmonic Cancellation Techniques for the On-Chip Implementation of Sinusoidal Signal Generators for Mixed-Signal BIST Applications

Harmonic cancellation strategies have been recently presented as a promising solution for the efficient on-chip implementation of accurate sinusoidal signal generators. Classical harmonic cancellation techniques consist in combining a set of time-shifted and scaled versions of a periodical signal in such a way that some of the harmonic components of the resulting signal are cancelled. This signal manipulation strategy can be easily implemented using digital resources to provide a set of phase-shifted digital square-wave signals and a summing network for scaling and combining the phase-shifted square-waves. A critical aspect in the practical implementation of the harmonic cancellation technique is the stringent accuracy required for the scaling weight ratios between the different phase-shifted signals. Small variations between these weights due to mismatch and process variations will reduce the effectiveness of the technique and increase the magnitude of undesired harmonic components. In this work, different harmonic cancellation strategies are presented and analyzed with the goal of simplifying the practical on-chip implementation of the scaling weights. Statistical behavioral simulations are provided in order to demonstrate the feasibility of the proposed approach.