A Novel Ferrofluidic Inclinometer

Inertial transducers based on the use of ferrofluids as inertial mass can be of great interest due to their peculiarities and due to the advantages that they show when compared to traditional devices. Ferrofluids are special solutions of magnetic particles in a carrier liquid whose density and other physical features can be controlled by an external magnetic field. In this paper, the development of a ferrofluidic inclinometer, which exhibits a tunable operating range and a valuable metrological feature and an intrinsic robustness against inertial shocks, is presented. The device consists of one excitation coil and two sensing coils wound around a glass pipe where a drop of ferrofluid is contained in a water environment. The magnetic force, which is induced by the excitation coil, attracts the ferrofluidic mass in a position that depends on the device inclination. The voltage at the output of the two sensing coils is related to the ferrofluidic mass displacement and thus reflects the tilt to be measured. Analytical models, simulations, and experimental results are presented to demonstrate the suitability of the proposed approach.     

Photonic Crystal Drop Filter Exploiting Resonant Cavity Configuration

Band dropping devices are widely used in WDM application. In this paper the design of a two-dimensional photonic crystal drop filter is proposed. Different from the configuration reported in literature which are realized by means of a photonic bandgap waveguide and one or more resonant cavities, able to select a signal at desired frequency, the proposed drop filters exploits a novel system of point defects. The design is based on the accurate analysis of higher order resonant modes supported by the system and their parities. The temporal and spectral behavior of the device is studied using plane wave expansion (PWE) and FDTD methods.     

A Resonant Micromachined Magnetic Field Sensor

The design, modeling, and simulation of a novel micromachined magnetic field sensor are discussed. The sensor uses an electrostatic resonator whose fundamental resonant frequency is modified by a Lorentz force generated from the interaction of the sensor structure and the present magnetic field. The sensor was fabricated in a standard bulk micromachining process without the need for any additional processing steps. Since the sensor does not employ any magnetic materials, it does not exhibit hysteresis. A comprehensive model of the sensor behavior is derived which encompasses the interactions of the involved physical domains. Validity of the modeling results was verified by finite-element simulations, and later, through experiments. The sensitivities of the fabricated sensors are in the range of 48-87 Hz/T, depending on sensor structure and dimensions. The design of the sensor allows for its fabrication in many standard microelectromechanical system processes and is compatible with CMOS processes. The theoretical minimum detectable signal with current devices is on the order of 217 nT. Methods to improve the sensitivity of the current sensors are suggested. A linear response to a wide range of magnetic fields makes this design suitable for applications where large fields need to be measured with high resolution.     

新型谐振式硅微机械加速度计

制作出一种新型结构的谐振式硅微加速度计，其输出频率信号可以克服微机电系统器件输出微弱信号检测的困难、采用双端固定音叉作为谐振器，在加速度作用下，质量块的惯性力通过悬臂梁施加于音叉轴向，利用音叉谐振频率的变化测量加速度．在每个音叉臂上制作了梳齿结构，用梳齿间的静电力激励音叉产生谐振，并利用其构成的电容检测其振动频率．该加速度计采用体硅工艺制作，文中给出了工艺流程、用有限元方法仿真估算，得到传感器的灵敏度约为2／gHz．     

A Resonant Micromachined Electrostatic Charge Sensor

A micromachined electrometer, based on the concept of a variable capacitor, has been designed, modeled, fabricated, and tested. The device presented in this paper functions as a modulated variable capacitor, wherein a dc charge to be measured is up-modulated and converted to an ac voltage output, thus improving the signal-to-noise ratio. The device was fabricated in a commercial standard SOI micromachining process without the need for any additional processing steps. The electrometer was tested in both air and vacuum at room temperature. In air, it has a charge-to-voltage conversion gain of 2.06 nV/e, and a measured charge noise floor of 52.4 e/rtHz. To reduce the effects of input leakage current, an electrically isolated capacitor has been introduced between the variable capacitor and input to sensor electronics. Methods to improve the sensitivity and resolution are suggested while the long-term stability of these sensors is modeled and discussed.     

测斜仪校准装置控制系统的设计和研发

针对测斜仪的结构原理和工作精度要求,设计和开发了一套测斜仪校准装置的自动控制系统。本装置采用电机驱动、圆光栅定位的机构模式,软件设计采用面向对象的程序设计语言C＋＋实现了整个系统的多项功能。     

激励功率对微机械谐振梁谐振频率的影响

对谐振式微机械传感器的敏感元件——微机械谐振梁的谐振频率特性进行了详细的实验研究,并从理论上分析了激励功率对谐振频率的影响．实验结果表明,谐振频率随着激励功率的增加而近似线性减小,当激励功率从1．1mW提高到10．1mW时,谐振梁的谐振频率降低了1．609kHz,灵敏度为0．179kHz／mW．实验结论与理论分析的结果基本一致．若要使激励功率对谐振频率的影响减小,则要求降低激励功率并减小梁的长度,增大梁的厚度和宽度．上述研究结论对优化谐振式微机械传感器敏感元件结构尺寸的设计有指导意义．     

一种新型硅微机械粘滞型谐振真空计

在对静电激励硅微机械谐振真空传感器研究的基础上，实现了一种新型的粘滞型谐振真空计。并给出了理论分析和实验结果。测试表明，其有效量程为1～1．33×103Pa。     

一种新型的谐振梁频率测量方法研究

谐振梁是一种应用广泛的谐振器。谐振式传感器可以通过测量谐振梁谐振频率的变化,解算谐振梁所受的轴向载荷的大小,从而达到测量目的。目前谐振梁常用的频率测量方法对于动态测量问题的效果并不理想,在很多应用场合都受到限制。本文针对双端固支型谐振梁的频率测量问题,设计了一种基于希尔伯特变换的频率测量方法。使用数值方法对谐振梁振动方程进行求解,获得多种典型的测试信号。仿真实验表明,该方法能很好地获取动态信号频率。     

基于双谐振环超表面的双波束天线

本文提出了一种基于双谐振环超表面的双波束天线.天线由两个相同的印刷偶极子贴片和超表面构成,超表面单元为双谐振环.该天线通过加载超表面实现了波束成形和波束偏转;同时,通过在偶极子贴片辐射臂旁边加入一排短路过孔,抑制了旁瓣,增加了波束的偏斜角度,还使天线的波束宽度变窄.另外,在基板上加载2×2的双谐振环阵列,提高了天线的增益.结果表明,天线谐振频率在3.5 GHz,-10 dB带宽为0.93 GHz,最大辐射波束指向(φ,θ)=(±155°, 90°),增益可达到8.02 dBi.     

A Novel Method to Read Remotely Resonant Passive Sensors in Biotelemetric Systems

Resonant passive sensors composed by resistive, inductive, and capacitive (RLC) simple sensors are widely used in biotelemetric systems. In this paper, a novel method to read remotely these RLC sensors is presented. The developed method is based on the simultaneous application of three excitation signals of same amplitudes, set at different frequencies, to determine remotely the RLC sensor resonance frequency and quality factor . Theoretical analysis and experimental results are also presented.     

A Novel Vector Hydrophone Based on the Piezoresistive Effect of Resonant Tunneling Diode

This letter reports a novel vector hydrophone based on the piezoresistive effect of resonant tunneling diode (RTD). An external pressure introduces stress in the layers of RTD and induces its current-voltage (I-V) curves change. This effect has been applied to designing new sensor. By control-hole technology, the sensor is processed integrated with GaAs/In_xGa_1-xAs/AlAs double barrier structures posited on its strain-sensitive region. The fabricated sensor is packaged for watertight solution, and underwater measurements are conducted in RTD's negative differential resistance (NDR) region. Directivity curve of the sensor follows ";8"; cosine functional form, which shows its vector sound signal detection ability, and its sensitivity reaches -184.6 dB (0 dB = 1 V/muPa) at 1 KHz.     

A SiC MEMS Resonant Strain Sensor for Harsh Environment Applications

In this paper, we present a silicon carbide MEMS resonant strain sensor for harsh environment applications. The sensor is a balanced-mass double-ended tuning fork (BDETF) fabricated from 3C-SiC deposited on a silicon substrate. The SiC was etched in a plasma etch chamber using a silicon oxide mask, achieving a selectivity of 5:1 and etch rate of 2500 Aring/min. The device resonates at atmospheric pressure and operates from room temperature to above 300degC. The device was also subjected to 10 000 g shock (out-of-plane) without damage or shift in resonant frequency. The BDETF exhibits a strain sensitivity of 66 Hz/muepsiv and achieves a strain resolution of 0.11 muepsiv in a bandwidth from 10 to 20 kHz, comparable to state-of-the-art silicon sensors     

Resonant bonding in crystalline phase-change materials

The identification of materials suitable for non-volatile phase-change memory applications is driven by the need to find materials with tailored properties for different technological applications and the desire to understand the scientific basis for their unique properties. Here, we report the observation of a distinctive and characteristic feature of phase-change materials. Measurements of the dielectric function in the energy range from 0.025 to 3 eV reveal that the optical dielectric constant is 70-200% larger for the crystalline than the amorphous phases. This difference is attributed to a significant change in bonding between the two phases. The optical dielectric constant of the amorphous phases is that expected of a covalent semiconductor, whereas that of the crystalline phases is strongly enhanced by resonant bonding effects. The quantification of these is enabled by measurements of the electronic polarizability. As this bonding in the crystalline state is a unique fingerprint for phase-change materials, a simple scheme to identify and characterize potential phase-change materials emerges.     

A Novel High-Speed Multiplexing IC Based on Resonant Tunneling Diodes

A new multiplexing IC based on the resonant tunneling diode (RTD) is proposed. The unique negative differential resistance characteristics arising from quantum effects of the RTD enable us to develop a new functional low-power digital circuit. The proposed multiplexing IC consists of two current-mode-logic monostable-bistable transition logic elements (CML-MOBILEs) based on the RTD and a low-power selector circuit block. The proposed circuit has been fabricated by using an InP RTD/ heterojunction bipolar transistor monolithic microwave integrated circuit technology. The multiplexing operation of the fabricated quantum effect IC has been confirmed up to 45 Gb/s for the first time as a monolithic technology based on the quantum effect devices. The dc power consumption is only 23 mW, which is found to be one-fourth of the current state-of-the-art conventional transistor-based multiplexing IC.     

Bragg Cell Diffraction in Resonant Cavities

Abstract

Steier et al. [1] have shown that the diffraction efficiency of a stationary grating may be improved by placing the grating in a resonant cavity. In this paper we describe the diffraction of light by a Bragg cell in a resonant cavity. Large improvements in diffraction efficiency are shown to be possible if scattering losses on the surface of the cell can be kept small. The effects of introducing gain into the cavity are calculated and the changes in bandwidth, resolution and dynamic range are discussed for the system when used as a radiofrequency spectrum analyser. A multichannel fibre optic system has been designed and is described.     

A Configuration of the Optical System for a 5 m Telescope

A configuration of the optical system for a 5 m telescope is described Its salient features are: (1) A common secondary mirror is used for all foci. (2) While used for each focus, the secondary mirror should be moved to a proper corresponding position. Thus the image quality at each focus can be obviously improved. (3) A specific ‘prime’ focus system has been developed. (4) A specific Nasmyth system has been developed. In this configuration the Cassegrain system is the Ritchey-Chrétien system. The spherical aberration and coma at each focus are eliminated simultaneously. At ‘prime’ focus the astigmatism is also eliminated simultaneously.     

A Family of Perfect Configuration Lenses of Revolution

A family of configuration lenses is described which collimate the rays from a point feed on a cone of varying aperture. The RCA «lamp-shade» (fig. 5), the RINEHAR -LUNEBRRO lens (fig. 7) and the sphere are members of this family. A fourth member is worth noticing (fig. 12) for its excellent scanning properties. SOMMAIRE. - Une famille de lentilles de «configuration» est décrite; ces lentilles permettent d'oblenir un faisceau de rayons parallèles à partir d'un point source (d'ondes courtes) placé sur un cône d'ouverture variable. L'abat-jour de la R. C. A., (fig. 5), la lentille de RINEHARr-LUNEBEnG (fig. 7) et la sphère en sont des cas particuliers. Un quatrième exemple (fig. 12) mérite d'être signalé pour ses excellentes possibilities d'exploration angulaire. ZUSAMMENFASSUNG. - Eine Gruppe on Konfigurationslinsen wild beschrieben, bei denen die on einem Punkt ausgehenden Strahlen in einen Kegel veränderlicher Apertur gebütl delt werden. Der R. C. A «Lampenschirm», (Abb. 5) die Linse nach RINEHART-LUNEBEPG (Abb. 7) und die Kugel gehören in diese Gruppe. Auch die Linse nach Abb. 12 gehört dazu and ist wegen ihrer guten Figenschaften besonders zu erwähnen.     

A Resonant Cavity Approach for the Nondestructive Determination of Complex Permittivity at Microwave Frequencies

A nondestructive microwave cavity approach for measuring complex permittivities of materials in sheet form is described. The resonant cavity is a section of a rectangular waveguide terminated by a thin rigid and large flange containing a small rectangular iris opening. The iris is placed in firm contact with one side of the dielectric sample while the other side is backed with a highly conducting plate. Variations of the cavity resonant frequency and Q-factor caused by the dielectric can be related to its complex permittivity through the consideration of equivalent admittance of this open-ended dielectricloaded aperture at resonance. Experimental determination of aperture admittance of a loaded iris is made and the results compared with theoretical calculations. The validity of this technique is confirmed by evaluating the resonant cavity characteristics by loading it with dielectrics of known permittivities and comparing the results with theoretical results. The permittivity of a lossy dielectric slab is measured and the value obtained by this method is compared with those found by other techniques. In all these cases the agreement between theory and measurements is satisfactory. Utility of this technique in evaluating the local inhomogeneities of permittivity of sheets is demonstrated. Measurement errors and limitations of this technique are pointed out.