Near-Field Loop Antenna for the UHF RFID Reader

A loop antenna for near field readers is proposed. Through periodic interdigital capacitors, the phase of the current on the loop is compensated and kept in phase. Hence, a loop with a perimeter of one wavelength at 900 MHz achieves a uniform near magnetic field distribution inside the loop. A novel method is proposed to evaluate the performance of the coplanar waveguide （CPW） to coplanar stripline （CPS） transition, which is used as a balun for the feeding network in this paper. This loop antenna has a 70 MHz operating bandwidth and 12 cm maximum reading range when the output power is 24 dBm, which is suitable for most near field radio frequency identification （RFID） applications.

Spin Supercurrent in Phenomena of Quantum Non-Locality (Quantum Correlations, Magnetic Vector Potential) and in Near-Field Antenna Effect

It is shown that such phenomena as quantum correlations (interaction of space-separated quantum entities), the action of magnetic vector potential on quantum entities in the absence of magnetic field, and near-field antenna effect (the existence of superluminally propagating electromagnetic fields) may be explained by action of spin supercurrents. In case of quantum correlations between quantum entities, spin supercurrent emerges between virtual particles pairs (virtual photons) created by those quantum entities. The explanation of magnetic vector potential and near-field antenna effect is based on contemporary principle of quantum mechanics: the physical vacuum is not an empty space but the ground state of the field consisting of quantum harmonic oscillators (QHOs) characterized by zero-point energy. Using the properties of the oscillators and spin supercurrent, it is proved that magnetic vector potential is proportional to the moment causing the orientation of spin of QHO along the direction of magnetic field. The near-field antenna effect is supposed to take place as a result of action of spin supercurrent causing secondary electromagnetic oscillations. In this way, the electromagnetic field may spread at the speed of spin supercurrent. As spin supercurrent is an inertia free process, its speed may be greater than that of light, which does not contradict postulates of special relativity that sets limits to the speed of inertial systems only.

Decoupling technique of patch antenna arrays with shared substrate by suppressing near-field magnetic coupling using magnetic metamaterials

In this paper,we propose the decoupling technique of patch antenna array by suppressing near-field magnetic coupling（NFMC） using magnetic metamaterials.To this end,a highly-integrated magnetic metamaterials,the substrate-integrated split-ring resonator（SI-SRR）,is firstly proposed to achieve negative permeability at the antenna operating frequency.By integrating SI-SRR in between two closely spaced antennas,magnetic fields are blocked in the shared substrate due to negative permeability of SI-SRR,reducing NFMC between the two antennas.To verify the technique,a prototype was fabricated and measured.The measured results demonstrated that the isolation can be enhanced by more than 17 dB even when the gap between the two patch antennas is only about 0.067 A.Due to high integration,this technique provides an effective alternative to high-isolation antenna array.

Mapping an on-chip terahertz antenna by a scanning near-field probe and a fixed field-effect transistor

In the terahertz（THz） regime,the active region for a solid-state detector usually needs to be implemented accurately in the near-field region of an on-chip antenna.Mapping of the near-field strength could allow for rapid verification and optimization of new antenna/detector designs.Here,we report a proof-of-concept experiment in which the field mapping is realized by a scanning metallic probe and a fixed AlGaN/GaN field-effect transistor.Experiment results agree well with the electromagnetic-wave simulations.The results also suggest a field-effect THz detector combined with a probe tip could serve as a high sensitivity THz near-field sensor.

Spherical Near-Field - Far-Field Transformation for Quasi-Planar Antennas from Irregularly Spaced Data

An effective near-field - far-field (NF - FF) transformation with spherical scanning for quasi-planar antennas from irregularly spaced data is developed in this paper. Two efficient approaches for evaluating the regularly spaced spherical samples from the nonuniformly distributed ones are proposed and numerically compared. Both the approaches rely on a nonredundant sampling representation of the voltage measured by the probe, based on an oblate ellipsoidal modelling of the antenna under test. The former employs the singular value decomposition method to reconstruct the NF data at the points fixed by the nonredundant sampling representation and can be applied when the irregularly acquired samples lie on nonuniform parallels. The latter is based on an iterative technique and can be used also when such a hypothesis does not hold, but requires the existence of a biunique correspondence between the uniform and nonuniform samples, associ- ating at each uniform sampling point the nearest irregular one. Once the regularly spaced spherical samples have been recovered, the NF data needed by a probe compensated NF - FF transformation with spherical scanning are efficiently evaluated by using an optimal sampling interpolation algorithm. It is so possible to accurately compensate known posi- tioning errors in the NF - FF transformation with spherical scanning for quasi-planar antennas. Some numerical tests assessing the accuracy and the robustness of the proposed approaches are reported.

Far-Field Pattern Reconstruction from Positioning Errors Affected Near-Field Data Acquired via Helicoidal Scanning

In this paper, an effective technique to compensate the positioning errors in a near-field—far-field (NF-FF) transformation with helicoidal scanning for elongated antennas is presented and validated both numerically and experimentally. It relies on a nonredundant sampling representation of the voltage measured by the probe, obtained by considering the antenna as enclosed in a cylinder ended in two half-spheres. An iterative scheme is used to reconstruct the helicoidal NF data at the points fixed by the representation from the acquired irregularly spaced ones. Once the helicoidal data have been retrieved, those needed by a classical NF-FF transformation with cylindrical scanning are efficiently evaluated by using an optimal sampling interpolation algorithm. Some numerical tests, assessing the accuracy of the approach and its stability with respect to random errors affecting the data, are reported. Experimental tests performed at the Antenna Characterization Lab of the University of Salerno further confirm the validity of the proposed technique.

平面近场测量中一种极化探头补偿算法研究

为研究天线特性,该研究采用近场测量技术计算天线的远场方向图,该技术具有成本低、速度快的优势。考虑到平面近场测量中探头参数对远场方向图的影响,该研究基于平面近远场变换算法,引入探头补偿技术和极化补偿技术。利用HFSS仿真得到待测天线远场仿真方向图,通过计算机算法构建,将近远场变换算法所得方向图与实际测得的远场方向图进行比较,验证算法的准确性。进一步结合极化补偿算法与探头补偿算法,与未修正的结果及远场方向图进行对比。结果显示,极化探头补偿算法能有效修正探头对远场方向图的影响,其不确定度超过近远场变换算法1.4295 dB,超过极化补偿算法0.9062 dB,确保了研究的客观性和独立性。

Brief Introduction of a New Kind of Glide Path Antenna

A new kind of image type glide path beacon subsystem of Instrument Landing System (ILS) was reported. Capture effect is designed to overcome far-field (FF) reflectors and rising terrain. Low angle CSB signal was highly depressed, was ?41 dB at 1? comparative to the max value. Both Carrier and Side Bands (CSB) and Side and Bands Only (SBO) signals were radiated by three antennas. Difference in Depth of Modulation (DDM) provided good linear variation around glide path angle (θ). At near field area, the site of near-field (NF) monitor was just about 57 m in front of the system, needed less length of reflection plane than that of M-array system, result from the system had only 90% of the M-Array antenna height.

双圆极化近场成像张量全息超表面

近场波束赋形可用于近场通信、无线功率传输等领域,而基于全息超表面设计的近场成像天线具有剖面低、无需馈电网络和波束调控灵活等优势。对标量和张量全息超表面近场成像进行了理论推导、仿真分析和实物验证。在此基础上,利用张量全息超表面设计了一款集成平面馈源的近场成像天线,全波仿真和测试结果相吻合,验证了该超表面具有可同时利用左旋和右旋圆极化进行近场成像的能力。

全光纤耦合式太赫兹近场探针光谱成像系统

通过对太赫兹光电导探针天线与飞秒倍频光路进行光纤模块化封装,并结合光纤耦合式太赫兹光电导天线辐射源,以及自主研制设计的光纤飞秒激光光源和光纤式高速光学延时线,开发了一种全光纤耦合式太赫兹近场探针光谱成像系统,其光谱范围覆盖0.1~2.0 THz,动态范围达到60 dB,光谱采样速度高达0.1 s/谱,近场成像分辨率优于20μm的全光纤耦合式太赫兹近场探针光谱成像系统。得益于整套系统的全光纤结构设计,太赫兹辐射源和探针式探测器之间可以根据测量需求灵活调节而不需要重新校准光路,极大地提高了系统的工作稳定性和使用方便性。该研究为太赫兹科学研究提供了一种高性能且实用性强的太赫兹近场光谱成像测量系统。

天线谐波和乱真输出辐射发射测量方法综述

基于天线有效辐射功率的基本原理,指导天线谐波和乱真辐射发射测量。通过对测量距离、系统校准以及相关器件的论述,更好地指导测量应用。结合测量中出现的问题,分析了造成问题的机理,给出了解决问题的方法。

基于三次样条插值法的柱面近场测量欠采样修正算法研究

为解决暗室近场测试效率低的问题,本文针对天线近场测量中高效测量方法进行了研究,提出了一种柱面近场欠采样恢复算法。该算法利用高精度的三次样条插值(cubic spline interpolation,CSI)法对未采样的点进行恢复,可减少采样点数,提高测试速度。此外,在柱面近场欠采样恢复CSI求解过程中充分利用系数矩阵的正定、对称等优良特性,使线性方程组的计算量从O(n^(3))降为O(n),大大提高了CSI的计算效率。最后使用插值后的近场幅度和相位结合柱面近远场变换理论求得天线远场方向图。为验证所提出算法的有效性,试验测试了天线样机,试验结果与理论分析一致。

天线方向图精密测量方法定量化对比研究

在微波遥感和深空探测等领域,人们期待能够获得精准的天线方向图以便通过反演可见度函数得到待观测目标的真实结果。因此,急需获得不同方向图测量方法的测量误差数值大小。从计量学角度,分别通过精密测量技术和仿真技术进行了定量化对比研究。标准增益喇叭天线的精密实测数据表明,在远场法、平面近场法和球面近场法中:1)球面近场法所得零深效果最好,远场法最差,平面近场法介于二者之间;2)平面近场法的有效角度范围位于±60°,超过该范围,截断误差急剧增大至无效;3)远场法在角度范围±80°以外出现明显波纹。另一项试验结果表明,球面近场法与紧缩场法的吻合效果更好,但前者所得曲线更光滑。对于线性阵列天线,通过仿真技术进行了量化对比分析。该定量化研究结果可供挑选天线测量系统种类和提升方向图测量水平。

基于插值的球面近远场变换精度提升方法

天线的远场方向图是研究天线特性的重要依据,近场测量技术能够通过天线的近场测量数据计算出天线的外推远场方向图,具有不依赖天气、成本低、速度快等优点,是一种有效的研究方法。有时探头故障、取样点间取样间隔过大或取样点不够密集会给结果带来较大的偏差。该文以球面近远场变换算法为基准,针对球面近场测量中探头有时出现故障的问题,利用HFSS仿真得到取样间隔不同的天线近场数据,利用计算机进行算法构建,通过将正常数据代入算法的手段验证球面近远场变换算法的正确性,而后引入双调和样条插值法对仿真出的问题近场测量数据进行修正,最后将所得结果与未修正前进行对比。对比结果表明,两方向的方向图平均误差分别减小了0.774 dB和1.3103 dB。

基于DMA阵列划分的低复杂度近场估计方法

针对引入动态超表面天线(Dynamic Metasurface Antenna,DMA)导致近场效应下角度和距离耦合带来计算复杂度提升的问题,提出一种基于DMA阵列划分的低复杂度近场估计方法。首先,建立DMA阵列结构下的近场接收信号模型;其次,对DMA阵列进行划分以构造适合GESPRIT算法的阵列接收信号结构,解耦角度和距离参数,实现低复杂度的处理方法;最后,调整DMA的相移矩阵,通过最大化信噪比提升DMA阵列的近场估计精度。仿真结果表明,该方法相比2D-MUSIC算法复杂度明显降低,且在信噪比为0 dB时估计精度性能提升30%。

基于平面近场的太赫兹天线方向图测量不确定度的评定方法及验证

面对太赫兹(Tera Hertz,THz)频段天线方向图校准需求,基于研建的太赫兹天线方向图测量装置,根据NIST经典平面近场测量不确定度分析模型,对天线平面近场测试的测量不确定度进行分析评定,并通过比较法对测量不确定度进行验证。实验结果表明,该评定方法在设定的实验频段可行,预计在更高频段依然适用。首先介绍基于平面近场的太赫兹天线方向图测量装置,然后对测量不确定度的误差来源进行分析,并与远场测量结果进行比较验证,继而对未来工作进行展望。

一种表面波衰减率测量方法研究

介绍了雷达吸波材料表面波衰减率的重要性以及测量方法,从雷达方程入手分析出近场条件下测量雷达散射截面(RCS)的各影响因素,通过分析得出发射天线和接收天线的波束宽度和间距成为近场测量RCS的重要误差来源。提出了增大方向图1 dB波束宽度并减小发射天线和接收天线间距来减小测量误差的方案,设计制作了8~12 GHz圆锥喇叭天线,具有良好的圆对称性,1 dB波束宽度达到22°。组建了近场RCS测试系统,以金属立方体作为目标开展了测试系统验证试验,与理论值相比RCS曲线峰值之差小于0.5 dB,平均值之差小于0.2 dB,具有较高的测量精度。使用组建的近场RCS测试系统开展表面波衰减率测量试验,与紧缩场测量结果之差为0.38 dB,实现了近场条件下表面波衰减率的准确测量。

中波广播天线近场区电磁辐射场强的空间分布测算

中波广播主要应用垂直极化波沿地面进行传播,其天线近场区电磁辐射空间分布较为复杂,会影响中波广播信号的传输距离和覆盖区域。基于此,利用参数估计算法计算天线近场区电磁辐射场强进行计算和分析,以形成对电磁辐射场强空间分布的数值型具象描绘。测算结果表明,中波天线的辐射功率、中波信号波长均会对天线近场区电磁辐射场强的空间分布产生不同程度的影响,为相关天线辐射功率研究提供参考。

流态天线辅助混合场通信中天线位置优化设计

为解决FA辅助的混合场无线通信系统中存在的FA移动导致用户在远近场通信中切换造成性能损失的问题,提出了系统和速率最大化的基站FA位置矩阵的粒子群优化方法。在算法外层优化粒子位置,根据位置判断用户处于远场或近场并采用相应方式建模信道;内层则采用ZF波束成形并计算适应度值。仿真结果表明,所提算法能有效应对FA移动引发的用户远近场变化特性,弥补性能损失。