膜电阻作为微波电路封装谐振模式抑制层

通常将微波电路置于金属封装之内.如果该封装波导谐振模恰好位于电路工作频率范围之内,电路与封装谐振模间的耦合将干扰电路的工作.在腔内放入覆有膜电阻的介质基片,可以有效地削弱封装谐振模,避免了放入吸波材料的传统方法给军用、宇航用毫米波电路带来的可靠性和机械加工难题.膜电阻的吸波性能取决于膜电阻方阻值和介质层厚度,使用数值方法计算得到应用该方法削弱后的最低阶封装谐振模的品质因数.     

The influence of substrate properties on microwave losses in thin films of semiconductors

A method is presented for the contactless measurement at microwave frequencies of the resistivity of thin films of semiconductors deposited on insulating substrates. The resistivity is determined through a measurement of the change in the power loss or Q of a microwave cavity upon insertion of the sample. In addition to the intended application, knowledge can be obtained about microwave power losses in supported thin films. Calculated microwave losses in the semiconductor films are presented in a normalized form as a function of the thickness and electrical properties of both the film and the supporting substrate at 9.0 GHz (X band) and 23.0 GHz (K band). These calculations were made for germanium on calcium fluoride and sapphire substrates. The power losses are normalized on a unit surface area and a unit surface field intensity basis. Limited experimental data are presented for germanium on calcium fluoride. The computed curves show that a maximum in power dissipation for a fixed substrate thickness and frequency is reached at higher and higher film resistivities as the film thickness increases. A very strong dependence of power loss on substrate thickness is demonstrated.     

强吸收衬底上薄膜厚度和折射率的测量新方法

提出了一种同时测量强吸收衬底上薄膜厚度和折射率的方法。对生长于强吸收衬底上的透明薄膜,提出在该薄膜上镀一层薄金属,形成金属-薄膜-强吸收衬底的类波导结构。由于小角度入射光在强吸收衬底上具有较强的反射率,使该结构可容纳一系列共振模。利用自由空间耦合技术和导出的共振模模式本征方程,同时确定透明薄膜的厚度和折射率。实验中测量了硅衬底上制备的聚甲基丙烯酸甲酯(PMMA)薄膜的折射率和厚度,测量的相对误差均小于10-3。该方法具有简便、可靠、可测量任意折射率薄膜的优点。     

聚酰亚胺覆盖层对LGS声表面波谐振器的影响

该文在硅酸镓镧(LGS)声表面波(SAW)谐振器上沉积了不同厚度的聚酰亚胺薄膜,研究了聚酰亚胺覆盖层对LGS声表面波谐振器的影响。结果表明,SAW谐振器表面沉积了聚酰亚胺薄膜后,器件的谐振频率向低频移动,且随着聚酰亚胺层厚度的增加,谐振器的谐振频率下降越大。SAW谐振器的一阶频率温度系数绝对值随着聚酰亚胺层厚度的增加而增大,且温度转变点向低温偏移。研究结果表明,覆盖聚酰亚胺层薄膜可以提高SAW谐振器的温度灵敏度,从而可应用于温度传感器中。     

The effect of superconducting ground plane on microwavecharacteristics of unpatterned superconducting films in the mixed state

We microwave characteristics of a multilayer structure made of a type-II superconducting thin film and a dielectric substrate together with a superconducting ground plane is studied theoretically by using the model of the self-consistent treatment of vortex dynamics. The dependence of reflection coefficient on the temperature and static magnetic field is reduced owing to the existence of the superconducting ground plane, especially at temperatures near T_c and at higher fields. Comparison of the interesting oscillation phenomenon in the associated effective surface resistance between the Meissner state (b=0) and mixed state (b≠0) is made. We find that the superconducting ground plane not only strongly narrows down the resonant peak shape but also enhances the peak height. Finally, a similar layered structure made of a superconducting thin film on a dielectric substrate shielded by a buffer layer is also considered. We specifically demonstrate that the buffer layer has essentially no substantial influence on microwave reflectance, transmittance, and complex surface impedance. The role played by the buffer layer is in great contrast to that in a planar transmission line     

薄膜体声波传感器的有限元仿真与分析

薄膜体声波滤波器(FBAR)传感器的性能受结构和材料特性的影响很大。该文利用COMSOL Multiphysics有限元仿真软件,建立了FBAR传感器的二维、三维有限元结构模型。用氮化铝和氧化锌材料作为压电薄膜对建立的模型做了固体力学和静电学仿真分析,得到了FBAR传感器的谐振频率、导纳特性曲线和谐振频率处的位移分布情况。通过分析发现氮化铝压电薄膜阻抗特性曲线更平滑,而氧化锌压电薄膜存在明显的寄生谐振峰的问题。针对氧化锌压电薄膜存在的寄生谐振峰进行了优化,仿真分析了电极边长尺寸和电极厚度对寄生谐振的影响,实现了对寄生谐振峰的有效抑制。     

A novel in situ monitoring technique for reactive ion etching usinga surface micromachined sensor

This paper presents a novel technique for monitoring film thickness in reactive ion etching by incorporating a micromachined sensor. The prototype sensor correlates film thickness with the change in resonant frequency that occurs in a micromachined platform during etching. The platform is suspended over a drive electrode on the surface of the substrate and electrically excited into resonance. As material is etched from the platform, its resonant vibrational frequency shifts by an amount proportional to the amount of material etched, allowing etch rate to be inferred. As a proof-of-concept experiment, a platform made of DuPont 2611 polyimide has been fabricated. The sensor is driven into resonance electrostatically, and the shift in resonance is detected by monitoring the change in impedance between the drive electrode and platform as the drive frequency is swept. To enhance filtering of the sensor signal in the noisy plasma environment, the platform is designed so that the ratio of the plasma frequency to the fundamental mode of vibration is approximately 400:1. The prototype was etched in a Plasma Therm 700 series reactive ion etching (RIE) system in a CHF₃/O₂ plasma. Electrical contact was made with the sensor using a feedthrough attached to the vacuum line beneath the process chamber to facilitate in situ excitation and measurement. The sensor is shown to offer high resolution (approximately 1300 Hz/um), potentially permitting accurate in situ monitoring of etch rate and uniformity at a nominal cost     

基于双开口环型的太赫兹超材料传感器设计

设计了一款可用于检测材料折射率及厚度的双开口环型太赫兹超材料传感器,其结构由双开口方环与圆环嵌套的超材料结构和聚酰亚胺衬底两部分构成.当太赫兹波垂直入射超材料表面时,该传感器结构在0.8～1.8 THz范围内形成三个高Q值谐振峰(中心频率分别为f1,f2和f3).通过探讨超材料结构表面电流分布与三个谐振峰形成的关系,观察到超材料结构对入射太赫兹波的不同响应特性导致产生不同的表面电流分布.此外,还对该传感器在折射率传感和厚度传感方面的应用进行了探究.在待测物厚度一定的情况下,该传感器在谐振频率f1,f2和f3处的传感灵敏度分别可达170,103和119 GHz/RIU,均具有优越的传感特性,可利用其多谐振峰进行高灵敏度折射率传感.这种高灵敏度的多谐振峰折射率传感器可以检测到待测分析物的微小变化,在生物化学检测领域具有广阔的应用前景.     

Modeling of planar quasi-TEM superconducting transmission lines

Design oriented modeling of high-temperature superconducting thin-film microwave circuits is difficult when film thickness is on the order of the penetration depth of the fields. Involved formulas for loss, phase velocity and characteristic impedance can be derived from the Bardeen-Cooper Schrieffer (BCS) theory of superconductivity. The parameters required by these formulas do not correspond to readily measurable observables that depend on the manufacturing process of the superconductor. An application of the phenomenological loss equivalence method in modeling the microwave behavior of planar quasi-TEM superconducting transmission lines is presented. Measured and modeled S-parameters of a superconducting coplanar waveguide lowpass filter agree to within 0.3 dB in magnitude and 0.5 radians in phase. Extracted values for the penetration depth and the real part of the conductivity of the superconducting film are within 10% of the findings of other researchers     

双峰效应光纤光栅薄膜传感器的优化设计

利用双峰谐振效应,通过在长周期光纤光栅(LPFG)包层表面涂覆一层对周围气氛敏感的薄膜,建立了一种新型薄膜传感器,其双峰谐振波长间隔随薄膜折射率的变化而变化.基于三包层光纤光栅物理模型,根据耦合模理论研究了传感器的灵敏度Sn与薄膜光学参数(折射率n3和厚度h3)和光纤光栅结构参数(光栅周期Λ、折变量σ)之间的关系.采用最优化数值方法,确定了最佳的膜层光学参数和光栅结构参数.计算表明,该类型传感器对膜层折射率的测量分辨率高达10-7.     

Modeling the microwave properties of superconductors

In this paper a macroscopic phenomenological model for the microwave properties of superconductors is presented. The model is based on the idea that there are two kinds of current carriers, and instead of the first London's equation a new equation is derived. This model can be applied to both low- and high-temperature superconductors. Using this model, an expression for the microwave surface resistance is derived and the surface resistance versus frequency is calculated. The results show that the relation between resistance and frequency is not R₃~ω² as indicated by both BCS theory and London model, but R_s~ω^a, where a is between 1 and 2 (e.g. a=1.35) for thin film high-T_c superconductors YBa₂Cu₃O_7-δ. The temperature dependence of R_s is simulated using the given model. These relations and the values of the surface resistance agree well with experimental results. A residual resistance may be interpreted from this model     

衬底温度对制备出CNT膜的影响

在陶瓷衬底上通过磁控溅射方法镀上金属钛层,用含铁杂质的氧化硅对钛层进行抛光,通过微波等离子体化学气相沉积（MPCVD）法在不同的温度下短时间里制备出CNT膜。利用扫描电子显微镜、拉曼光谱,X射线衍射,分析了薄膜的结构和表面形貌。仔细研究不同温度下制备的CNT膜,得出衬底温度400℃时制备的碳膜是以非晶碳为主,600℃时置备的碳膜是良好的碳纳米管膜,800℃制备的碳纳米管膜的缺陷变得很多,以碳纳米链为主。最后得出了温度对催化活性有很大影响的结论。     

Coplanar Waveguide: A Surface Strip Transmission Line Suitable for Nonreciprocal Gyromagnetic Device Applications

A coplanar waveguide consists of a strip of thin metallic film on the surface of a dielectric slab with two ground electrodes running adjacent and parallel to the strip. This novel transmission line readily lends itself to nonreciprocal magnetic device applications because of the built-in circularly polarized magnetic vector at the air-dielectric boundary between the conductors. Practical applications of the coplanar waveguide have been experimentally demonstrated by measurements on resonant isolators and differential phase shifters fabricated on low-loss dielectric substrates with high dielectric constants. Calculations have been made for the characteristic impedance, phase velocity, and ripper bound of attenuation of a transmission line whose electrodes are all on one side of a dielectric substrate. These calculations are in good agreement with preliminary experimental results. The coplanar configuration of the transmission system not only permits easy shunt connection of external elements in hybrid integrated circuits, but also adapts well to the fabrication of monolithic integrated systems. Low-loss dielectric substrates with high dielectric constants may be employed to reduce the longitudinal dimension of the integrated circuits because the characteristic impedance of the coplanar waveguide is relatively independent of the substrate thickness; this may be of vital importance for Iow-frequency integrated microwave systems.     

矩形波导中圆柱介质谐振器的精确分析

本文分析了一种新型实用的微波滤波器结构:在矩形波导中插入圆柱形介质谐振器。文中将谐振器作为波导中的不均匀性,用模匹配法准确分析了其散射特性。理论结果不仅能计算谐振频率,而且还给出散射矩阵等网络参数。本文的理论分析与实验检测量结果吻合很好。通过理论与实验研究,本文对衬底的作用作出了新的解释。     

Analysis of a cylindrical-rectangular microstrip structure with anairgap

The resonance problem of the cylindrical-rectangular microstrip structure with an airgap between the substrate layer and the ground conducting cylinder is studied by using a rigorous full-wave approach and a moment method calculation. The resonance condition is satisfied by complex resonant frequencies, which provide the information of resonant frequency and half-power bandwidth of the structure. Numerical results indicate that, with the increasing of the airgap thickness, the half-power bandwidth of the structure at the efficient radiating mode of HE_0.1 is considerably increased, which improves the narrow bandwidth characteristics of microstrip structures. Details of the numerical results, including the results for the planar rectangular microstrip structure with an airgap, are presented and analyzed     

A study of cylindrical resonant structures constructed from frequency-selective surfaces

An experimental parametric study of frequency selective guides, cylindrical structures constructed from square loop frequency selective surfaces, is presented. Square loop resonators on a thin dielectric substrate are used for the frequency selective surface. The guides are intended for use in applications where lightweight, low cost and narrow band radiating systems are required. Comments on the manufacture of the guides are made. Propagating and radiating regions of the structures are described. The effects of the thickness of the supporting substrate thickness are clearly displayed (shifting the resonant frequency), as is the dependence of the propagation loss at resonance on the number of resonators on the circumference of the guide. The thickness of the supporting substrate shows a smaller effect on loss. Frequency scanning in the radiation region is also clearly established. Complex propagation constants are obtained from the experimental results, using three methods. The 'short circuit radiation pattern' method gives results that correlate best with simulated results. The guides show guidance over a frequency band determined by the frequency selective surface resonance. They also demonstrate a frequency scanning radiation broadside to the guidance direction.     

基于不同金属衬底制备碳膜的场发射研究

利用磁控溅射的方法,在相同的陶瓷衬底上面分别镀上三种不同金属,形成三种不同的金属衬底,对金属层进行相同的表面处理后,放入微波等离子体化学气相沉积腔中,制备出三种碳膜。对制备出不同的碳膜用扫描电镜、拉曼光谱、X射线衍射仪进行结构分析,并用二极管型结构测试了它们的场致发射电子的性能。找到了最适合场发射的金属衬底,进一步对不同金属衬底制备碳膜的场发射特性不同的原因进行了初步的研究。     

SPR生物传感器研制及谱的分析

本文描述了表面等离激元共振（ＳＰＲ）原理,并给出详细的ＳＰＲ测量系统硬件及软件框图。最后对棱镜－金属膜－电介质层的ＳＰＲ谱进行了解析。     

双金属层表面等离子体共振传感器灵敏度优化

为了优化表面等离子体共振传感器的灵敏度,基于薄膜光学理论,分析了银-金双金属层表面等离子体共振传感器的反射率和灵敏度随金属薄膜厚度变化的规律。发现在满足共振角反射率小于1%的条件下,银膜和金膜厚度存在一定的取值范围; 在此厚度范围内,传感器的灵敏度随着金属薄膜（银膜与金膜）厚度的增大而提高,灵敏度增量最大可达5°/RIU。结果表明,在保证一定共振角反射率的前提下,可通过增加双金属层中金属薄膜的厚度提高双金属层表面等离子体共振传感器的灵敏度。