基于极化变换谐振器的远距无芯片RFID湿度传感器设计

提出了一种用于远距离传感的无芯片RFID湿度传感器的设计.设计采用极化变换谐振器,用于减小周围环境对标签响应的影响,提高了传感器的可靠性.传感器标签集成了可实现极化变换的双螺旋条带和四组弯曲哑铃形条带,分别作为湿度传感谐振器和编码谐振器,能够在3.1 GHz~10.6 GHz的超宽带频率范围内产生5个谐振峰.传感谐振器表面涂覆的PVA材料层在湿度变化时影响谐振频率,实现湿度传感.谐振器标签布局紧凑,便于组成阵列形式以提高其雷达散射截面(RCS),实现远距离传感.仿真和实测结果表明,该传感器在1.4 m的阅读距离时可实现较为灵敏的湿度传感功能.传感器整体性能良好,具有较广的应用前景.     

角度编码柔性无芯片标签的散射特性及识别

本文研究了一种角度编码的柔性无芯片标签的散射特性.该标签的V形散射体包含两条金属臂,利用两臂之间的空间角度进行编码.通过测量标签在谐振频率上的正交散射场分量,即可识别标签.即使标签在自身所在表面上发生旋转,也能够被准确识别;分析了标签粘贴在曲面物体上,物体弯曲半径和物体相对介电常数对识别结果的影响,以及准确识别标签的情况下,收发装置之间的最大夹角.     

空间角度编码的无芯片射频识别缝隙标签的设计

本文提出了两种新型的基于空间角度编码的无芯片(Radio Frequency Identification,RFID)缝隙标签.标签利用金属平面上条形缝隙与水平极化方向的夹角进行编码.通过检测水平和垂直两个极化方向上的反向散射电场实现对标签角度信息的识别.结果表明:线形缝隙标签的角度识别误差均小于2°,V形缝隙标签的角度识别误差均小于3°,编码容量均可达4bit.标签结构简单,制作成本低;工作时占用频带窄,大大提高了频谱利用率.     

微扰和标定技术测量薄膜微波介电常数

提出了一种测量介质薄膜微波段介电常数的方法.该方法基于金属空腔谐振器微扰理论,用已知介电常数的基片作为标样,标定测量系统的有关参数,然后分别测量空腔、基片插入空腔、镀有介质薄膜的基片插入空腔三种情况下的谐振腔谐振频率,计算出镀覆于基片上介质薄膜的微波复介电常数.本文SiO2和MgTiO3-CaTiO3(MCT)介质陶瓷薄膜作了实验测量验证,结果表明该方法具有良好的测量精度(小于6%).     

一种谐振式露点测量方法

针对大气湿度测量问题,提出一种基于谐振式的露点测量方法,并设计了一套独立的露点传感装置.利用QCM原理将石英晶体谐振器作为湿敏元件,用半导体制冷器对其进行制冷,使其表面出现结露现象,导致石英晶体谐振器的谐振频率出现突变,以此达到对露点的识别,同时测取结露时刻石英晶体表面的温度,从而获得当前环境下的露点温度.通过实验验证了此方法的可行性与准确性,并将获取的实验数据与实际提供的环境数据进行对比分析,相对湿度误差达到±1.37%RH,此方法具有精度和灵敏度双高的优点,并且成本低、可操作性强.     

一种基于光纤F-P腔的石墨烯谐振式压力传感器

谐振式传感器具有良好的重复性、分辨率和稳定性,全光纤谐振式微型传感器则集合了微纳结构与光纤传感特性两者的优点。石墨烯作为近年来发现的一种新型材料,具有良好的热学和力学特性,可以作为谐振式传感器中的敏感元件。本文提出了一种基于光纤F-P结构的石墨烯谐振式压力传感器,其兼具微机械传感器和光纤谐振器的优点,具有较高的谐振频率,在测量压力的实验中展现出良好的性能,压力灵敏度最高可达2. 93Hz/Pa,具有重要的应用价值。     

“王”字型左手材料结构的设计与仿真

针对目前由金属开口谐振环与金属杆构成的左手材料结构存在构造比较复杂、工艺实现较难的缺点,设计实现了一种基于金属条的改进结构-"王"字型结构。通过理论分析和电磁仿真软件Ansoft HFSS 10模拟仿真,利用散射参量法提取参数结果表明该结构可以在X波段实现介电常数和磁导率同时为负。讨论研究了该左手结构的金属条宽度、中间缺口宽度、中间条宽度三个结构尺寸参数变化对谐振频率和透射峰幅值的影响,结果表明三个参数的变化都会对二者产生影响,其中金属条宽度改变对透射峰值影响幅度相对较大,缺口宽度改变对谐振频率影响幅度相对较大。     

基于Pierce振荡器架构的BAW传感器读出电路

薄膜体声波谐振器(FBAR)不仅能作为手机射频前端的滤波器,还具有充当传感器表头的潜力。为实现对体声波(BAW)传感器输出射频信号的检测,设计一种基于Pierce振荡器的BAW传感器读出电路。读出电路采用双路差分方式,将体声波谐振器构成两路振荡器,一路作为参考电路用于检测外界环境等因素的干扰,另一路作为传感电路用于检测待测物理量。两路振荡器信号通过混频滤波得到由待测物理量引起的谐振频率偏移。然后通过放大与整形将模拟信号转换为数字信号,最后送入FPGA进行频率检测。以一个2 GHz的体声波质量传感器为例,给出电路各模块的设计方法,经各模块仿真以及信号转换电路的实验验证,电路可检测的最大谐振频率偏移量为99 MHz。     

基于十字线与双开口环结构的双频段左手材料

本文提出一种将十字线与双开口环相结合的微波双频段左手材料,在介质基板正反两面刻蚀相同的十字线与双开口环,组成两个不同的谐振器.通过高频电磁仿真软件HFSS对其电磁特性进行数值研究.结果表明:当电磁波垂直于入射时,在两个磁谐振器上出现两个相应的电磁谐振而导致双频段的负折射率,且具有负的介电常数和负的磁导率,表现为左手特性.同时,通过对谐振点处电流分布图分析,进一步验证了仿真结果的正确性.最后讨论了该材料的主要结构参数对谐振特性的影响.     

硅微谐振式加速度计的温度效应及补偿

零偏和标度因数稳定性是衡量加速度计性能的两个重要参数.为了降低硅微谐振式加速度计的温度敏感性,对其温度影响机理进行了深入研究.通过温度实验发现,硅微谐振式加速度计的零偏和标度因数与设计理论参数有较大区别,且都具有较大的温度灵敏度,分别为0.72 g/℃和1.5℃-1.对弹性模量和谐振器应力与谐振器频率的关系进行了理论计算和FEA仿真验证,其中弹性模量引起的谐振频率-温度灵敏度为-0.7 Hz/℃,谐振器应力引起的谐振频率-温度灵敏度为180 Hz/℃.阐述了加工过程中键合应力产生的原因以及键合应力与谐振器残余应力的关系,发现谐振器应力是造成加速度计输出随温度漂移的主要因素.提出了一种隔离残余应力的隔离梁的设计方案,可使零偏温度灵敏度降至-35 Hz/℃,为温度补偿指明了方向.     

Dielectric constant measurement of low loss liquids using stacked multi ring resonator

The concept of dielectric constant measurement has been extended and applied in agriculture, pharmaceutical and food industry for quality control of liquids. Dielectric analysis of material at microwave frequencies can be done using novel shielded stacked multi-ring resonator (SMRR). The dielectric constant of liquids and paste has been calculated using SMRR with greater accuracy than the planar resonator, boxed resonator and stacked resonator. SMRR contains a ring resonator with fed patch and parasitic patch with different numbers and sizes of rings. The dimensions of rings on the parasitic patch are optimized to achieve Quality factor Q greater than 100 and return loss less than ?2 dB. Due to dual resonance in novel SMRR, structure losses are reduced by 50% than planar resonator structure. The behavior of SMRR structure at the 2.45 GHz frequency is studied with E field and H field. 3D model is designed in Computer Simulation Technology Microwave Studio (CST MWS) using TLM (Transmission Line Modeling) solver. Electromagnetic field analysis as well as impedance bandwidth of SMRR using CST MWS 3D model prove that electromagnetic coupling in SMRR structure increases thus improves quality factor. In SMRR quality factor increases and losses reduce help us to predict the complex permittivity of material for quality analysis.     

Characterizing nonlinear resonant structures

A method for the characterization of nonlinear resonant systems is proposed, which is based on the measurement of the transfer coefficient as a function of the frequency at constant amplitude of oscillations in the resonator. In this case, the amplitude-dependent characteristics of the nonlinear resonator, such as the level of losses and the resonance frequency, are the same for all points of the measured resonance curve. This situation can be realized by carrying out the measurements at a fixed output power. The resonance curve measured using this approach, in contrast to the standard amplitude-frequency characteristic obtained at a constant input power, has a Lorentz shape even for a strongly nonlinear system (irrespective of the operative mechanism of nonlinearity), which allows the Q value to be correctly defined (so that it will be constant for the entire measured resonance curve) and determined. The proposed method is illustrated by measuring the characteristics of a superconducting filter in a nonlinear regime.     

Simple design rules for optimal design of dielectric temperature-compensated sapphire resonators

It has been shown that the use of two dielectric crystals with opposite temperature coefficient of permittivity allows the realization of a resonator with a zero temperature coefficient of frequency. By using sapphire and rutile materials, which have low-loss tangents, some compensated resonators with very high Q-factors have been realized. In this work we develop rules that greatly simplify the design of a dielectric-compensated resonator. We show that the optimum design for compensation at a specific temperature may be determined by simply selecting the aspect ratio of the sapphire resonator.     

Phase‐Modulated Scattering Manipulation for Exterior Cloaking in Metal–Dielectric Hybrid Metamaterials

Artificially structured metamaterials with metallic or dielectric inclusions are extensively studied for exotic light manipulations via controlling the local‐resonant modes in the microstructures. The coupling between these resonant modes has drawn growing interest in recent years due to the advanced functional metamaterial making the microstructures more and more complex. Here, the suppression of magnetic resonance of a dielectric cuboid, an analogue to the scattering cancellation effect or radiation control system, realized with an exterior cloaking in a hybrid metamaterial system, is demonstrated. Furthermore, the significant modulation of the absorption of the dielectric resonator in the hybrid metamaterial is also demonstrated. The physical insight of the experimental results is well illuminated with a classical double‐harmonic‐oscillator model, from which it is revealed that the complex coupling, i.e., the phase of coupling coefficient, plays a crucial role in the overall response of the metal–dielectric hybrid system. The proposed design strategy is anticipated to form a more straightforward and efficient paradigm for practical applications based on radiation control via versatile mode couplings.     

High Security Identity Tags Using Spiral Resonators

A highly compact chipless tag based on Frequency coding technique using Spiral Resonators is proposed in this paper. Spirals are well known metamaterial structures and thus capable of sharp resonance, and hence Spiral Resonators can serve as a good candidate for RF Identity Tags. The bit capacity of the proposed tag is 10 bits per sqcm. The prototype of the tag is fabricated on a low-cost substrate of dielectric constant 4.4 and loss tangent 0.02. The overall dimension of tag is 15.4 x 3 x 1.6 mm³. Two methods for reading the tags are also discussed in this paper. Scope for bit enhancement is also provided.     

Rarefaction of the spectrum of H-type whispering-gallery modes in a hemispherical dielectric resonator

A dense spectrum of H-type resonance oscillations (whispering-gallery modes) is observed in a hemispherical dielectric resonator excited by a capacitive slit situated on the equatorial metal mirror surface. The spectrum can be significantly rarefied by exciting the WG modes in the resonator by means of distributed coupling to a dielectric waveguide arranged in a certain special position relative to the hemisphere base.     

Precise determination of the dielectric constant and thickness of a nanolayer by use of surface plasmon resonance sensing and multiexperiment linear data analysis

Surface plasmon resonance (SPR) sensing and an enhanced data analysis technique are used to obtain precise predictions of the dielectric constant and thickness of a nanolayer. In the proposed approach, a modified analytical method is used to obtain initial estimates of the dielectric constants and thicknesses of the metal film and a nanolayer on the sensing surface of a SPR sensor. A multiexperiment data analysis approach based on a two-solvent SPR method is then employed to improve the initial estimates by suppressing the noise in the measurement data. The proposed two-stage approach is employed to determine the dielectric constant and thickness of a molecular imprinting polymer nanolayer. It is found that the results are in good agreement with those obtained with an ellipsometer and a high-resolution scanning electron microscope.     

Conical quasioptical dielectric resonator

A dielectric resonator of the new type—conical quasioptical dielectric resonator—is proposed. The dependence of the resonance oscillation frequency, the quality factor, and the electric field distribution on the cone angle of such a resonator with a conducting screen in the base plane has been experimentally studied in the 8-mm (Ka-band) wavelength range.     

Temperature tunable metamaterial absorber at THz frequencies

Dynamic or active control over the resonance frequency of the perfect metamaterial absorbers have attracted considerable attention, and many kinds of frequency tunable absorbers have been proposed. Unfortunately, these designed absorbers have drawbacks of very small frequency tuning range as well as complex unit structure. In this paper, a simple design and large frequency change range of terahertz metamaterial absorber is investigated. The absorber structure consists of only a patterned square metallic patch and an appropriate thickness of the dielectric spacing slab on top of a metallic board. Results show that the frequency tuning range of the metamaterial absorber can be up to 80.4%, which is much greater than that of the existing absorbers (no more than 30%). The continuous shift of the resonance frequency can be explained by the temperature dependent dielectric m. Besides, we also found that the presented design strategy is a genetic method and can apply to other types of structure designs. The simple design and wide frequency tuning range of the absorbers could find potential applications in materials detection, biological sensing, and frequency selective thermal emitters.     

Analysis of piezoelectric bulk-acoustic-wave resonators as detectors in viscous conductive liquids

An analytical solution for the resonance condition of a piezoelectric quartz resonator with one surface in contact with a viscous conductive liquid is presented. The characteristic equation that describes the resonance condition and accounts for all interactions including acoustoelectric interactions with ions and dipoles in the solution is obtained in terms of the crystal and liquid parameters. A simple expression for the change in the resonance frequency is obtained. For viscous nonconductive solutions, the frequency change is reduced to a relationship in terms of the liquid density and viscosity. For dilute conductive liquid, the change in frequency is derived in terms of the solution conductivity and dielectric constant. The boundary conditions for the problem are defined with and without the electrical effects of electrodes. Experiments were conducted with various viscous and conductive chemical liquids using a fabricated miniature liquid flow cell containing an AT-cut quartz crystal resonator. The results, which show good agreement with the theory, on the use of quartz crystal resonators as conductivity and/or viscosity sensors are reported.