Showing papers on "Capacitive sensing published in 2004"

Analytical evaluation of the interdigital electrodes capacitance for a multi-layered structure

Abstract: The widespread use of interdigital electrodes in such applications as microwave filters, surface acoustic wave devices, electro-optic shutters as well as on chemical and biological sensing and even on the electrical and dielectric characterization of materials requires that we improve our description of their electrical performance. In this paper, we present new analytical expressions for the capacitance between the two comb electrodes of a periodic interdigital capacitive sensor, based on conformal mapping techniques. This proposed model is general and quite independent of the particular application and can be applied for any space and finger width as well as for any number of layers with different thickness and permittivity. The capacitance for a particular sensor configuration is a function of the dielectric permittivity of the materials, the fingers length and of two geometric non-dimensional parameters: (i) the ratio between the space and finger widths; (ii) the ratio between the thickness of the sensitive layer and the spatial sensor wavelength. Comparisons with previously published models as well as with experimental data and finite element analysis were made.

A low-noise low-offset capacitive sensing amplifier for a 50-/spl mu/g//spl radic/Hz monolithic CMOS MEMS accelerometer

Abstract: This paper describes a CMOS capacitive sensing amplifier for a monolithic MEMS accelerometer fabricated by post-CMOS surface micromachining. This chopper stabilized amplifier employs capacitance matching with optimal transistor sizing to minimize sensor noise floor. Offsets due to sensor and circuit are reduced by ac offset calibration and dc offset cancellation based on a differential difference amplifier (DDA). Low-duty-cycle periodic reset is used to establish robust dc bias at the sensing electrodes with low noise. This work shows that continuous-time voltage sensing can achieve lower noise than switched-capacitor charge integration for sensing ultra-small capacitance changes. A prototype accelerometer integrated with this circuit achieves 50-/spl mu/g//spl radic/Hz acceleration noise floor and 0.02-aF//spl radic/Hz capacitance noise floor while chopped at 1 MHz.

A comprehensive model to predict the charging and reliability of capacitive RF MEMS switches

Abstract: Reliability issues currently hamper the commercialization of capacitive RF MEMS switches. The most important failure mode is parasitic charging of the dielectric of such devices. In this paper we present an improved analytical model that enables us to calculate and understand the effect of insulator charging on the behavior of capacitive RF MEMS switches, and to describe the way they fail, and their reliability. Emphasis is placed on a shift of the pull-out voltage to predict failures. Tests with capacitive RF MEMS switches have been performed that validate the most important features of the model.

High-temperature single-crystal 3C-SiC capacitive pressure sensor

Abstract: Single-crystal 3C-silicon carbide (SiC) capacitive pressure sensors are proposed for high-temperature sensing applications. The prototype device consists of an edge-clamped circular 3C-SiC diaphragm with a radius of 400 /spl mu/m and a thickness of 0.5 /spl mu/m suspended over a 2-/spl mu/m sealed cavity on a silicon substrate. The 3C-SiC film is grown epitaxially on a 100-mm diameter silicon substrate by atmospheric pressure chemical vapor deposition. The fabricated sensor demonstrates a high-temperature sensing capability up to 400/spl deg/C, limited by the test setup. At 400/spl deg/C, the device achieves a linear characteristic response between 1100 and 1760 torr with a sensitivity of 7.7 fF/torr, a linearity of 2.1%, and a hysterisis of 3.7% with a sensing repeatability of 39 torr (52 mbar). A wide range of sensor specifications, such as linear ranges, sensitivities, and capacitance values, can be achieved by choosing the proper device geometrical parameters.

Anti-entrapment system

Abstract: An anti-entrapment system for preventing objects from being entrapped by a translating device includes a capacitance sensor positioned adjacent to the translating device and a controller. The sensor has first and second conductors separated by a separation distance and a compressible dielectric element interposed between the conductors. The conductors have a capacitance dependent upon the separation distance. The capacitance of the conductors changes in response to a geometry of the sensor changing as a result of either conductor or the dielectric element deforming in response to a first object touching the sensor. The capacitance of the conductors changes in response to a second conductive object coming into proximity with either conductor. The controller receives a signal from the sensor indicative of the capacitance of the conductors, and controls the translating device as a function of the capacitance of the conductors to prevent the translating device from entrapping either object.

Capacitance detector circuit, capacitance detection method, and fingerprint sensor using the same

Abstract: A capacitance detecting circuit of a capacitive sensor having a plurality of column lines and a row line intersecting the column lines detects a change in capacitance at an intersection of a column line and a row line. The circuit includes a PN code generating unit for generating a code having orthogonality in time sequence to output the generated code as a column drive signal, a column line drive unit for driving a predetermined one of the column lines which are selected in response to the code, a capacitance detecting unit, connected to the row line, for detecting a voltage by converting a total sum of changes in capacitance at intersections of the selected column lines into the voltage to output the detected voltage, and a decode processing unit for performing a predetermined calculation on the detected voltage output from the capacitance detecting unit and the code to determine a voltage value responsive to the capacitance change at the intersection.

Capacitive sensing of droplets for microfluidic devices based on thermocapillary actuation

Abstract: The design and performance of a miniaturized coplanar capacitive sensor is presented whose electrode arrays can also function as resistive microheaters for thermocapillary actuation of liquid films and droplets. Optimal compromise between large capacitive signal and high spatial resolution is obtained for electrode widths comparable to the liquid film thickness measured, in agreement with supporting numerical simulations which include mutual capacitance effects. An interdigitated, variable width design, allowing for wider central electrodes, increases the capacitive signal for liquid structures with non-uniform height profiles. The capacitive resolution and time response of the current design is approximately 0.03 pF and 10 ms, respectively, which makes possible a number of sensing functions for nanoliter droplets. These include detection of droplet position, size, composition or percentage water uptake for hygroscopic liquids. Its rapid response time allows measurements of the rate of mass loss in evaporating droplets.

Prospects for Fibre Bragg Gratings and Fabry-Perot Interferometers in fibre-optic vibration sensing

Abstract: Vibration monitoring of machinery is reducing the overall operating costs of industrial plants. Conventional vibration sensors, based on capacitive or piezoelectric principles, are limited in application due to the problem of electrical isolation. Fibre-optic based instrumentation is thus an attractive alternative method of vibration measurement in the vicinity of electrical substation. This paper discusses several techniques of vibration sensing using optical fibre technology and assesses their potential for use on electromechanical equipment. Firstly an overview of sensor based on In-Fibre Bragg Gratings is presented, and its potential for the measurement of strain and vibration is assessed. Secondly, vibration sensing using fibre-optic intensity-based measurement is presented and then Fabry-Perot Interferometer (FPI) for vibration sensing is critically reviewed. Of these, the FPI is the most attractive since it can easily be configured within a reflective fibre-optic probe. However, reported FPI sensors have been highly sensitive to measurement errors caused by mechanical vibration, temperature, and acoustic waves. This paper reviews technological developments of FPI to vibration sensing in extreme electromechanical environments and also for non-contact measurement. Finally this paper presents an overview of dual-wavelength technique for assessment of vibration signature.

A novel capacitive-type humidity sensor using CMOS fabrication technology

Abstract: This paper reports a novel capacitive humidity sensor integrated on a polysilicon heater. The sensor was fabricated with the industrial standard CMOS process to achieve a cost-effective solution for accurate and reliability. The sensing material polyimide was obtained by a post-processing step after the standard CMOS fabrication. The sensing principle of the sensor is based on the dielectric constant change of deposited polyimide due to absorption/desorption of vapor. The passivation (silicon nitride) layer with no limitations to the electrode selection is between the electrode and sensing material in order to improve the reliability of the relative humidity for the sensors. The humidity sensor was measured to show a linear dependence on the relative humidity in the range of 20–70%, the maximum hysteresis is 3%.

Precision readout circuits for capacitive microaccelerometers

Abstract: This paper presents a review of capacitive readout front-end circuits for high-precision accelerometers. The primary design parameters and the trade-offs affecting the resolution are presented. The discussions apply to all capacitive microsensor interfaces. Also, a high-sensitivity capacitive accelerometer interface circuit for hybrid-integration with a surface/bulk micromachined micro-g accelerometer is described. The first generation of the circuit resolves 75 aF of capacitance on /spl sim/120 pF parasitic capacitance with a 200 kHz sampling rate, and the second generation resolves 20 aF with 1 MHz sampling rate. The overall sensor-circuit module has a noise floor of 1.6 /spl mu/g//spl radic/Hz at ambient atmosphere.

Electrokinetic micropump and micromixer design based on ac faradaic polarization

Abstract: A microfluidic pump and mixer design based on ac faradaic polarization is proposed. Unlike ac electrokinetic devices based on capacitive charging of the electrodes, the design yields a net electro-osmotic flow for high-conductivity electrolytes at high voltages and frequencies without producing gas bubbles or generating pH gradients. The average velocity, which can be more than an order of magnitude higher than that generated by the capacitive mechanism, has an exponential dependence on the voltage and increases monotonically at low frequencies. Vortices and net flows with linear velocities in excess of 1mm∕s are generated with orthogonal microfabricated planar electrodes based on the unique flow and polarization features of this new ac charging mechanism.

Full-Lagrangian schemes for dynamic analysis of electrostatic MEMS

Abstract: Dynamic analysis of microelectromechanical systems (MEMS) is characterized by the nonlinear coupling of electrical and mechanical domains. The nonlinear coupling between the two domains gives rise to several interesting dynamic phenomena besides the well established pull-in phenomenon in electrostatic MEMS. For proper understanding and detailed exploration of MEMS dynamics, it is important to have a reliable and efficient physical level simulation method. In this paper, we develop relaxation and Newton schemes based on a Lagrangian description of both the mechanical and the electrical domains for the analysis of MEMS dynamics. The application of a Lagrangian description for both mechanical and electrostatic analysis makes this method far more efficient than standard semi-Lagrangian scheme-based analysis of MEMS dynamics. A major advantage of the full-Lagrangian scheme is in the accurate computation of the interdomain coupling term (mechanical to electrical) in the Jacobian matrix of the Newton scheme which is not possible with a semi-Lagrangian scheme. The full-Lagrangian based relaxation and Newton schemes have been validated by comparing simulation results with published data for cantilever and fixed-fixed MEM beams. The Newton scheme has been used for the dynamic analysis of two classes of comb-drives widely used in MEMS, namely, transverse and lateral comb-drives. Several interesting MEM dynamic phenomena and their possible applications have been presented. Spring-hardening and softening of MEM devices has been shown. The existence of multiple resonant peaks in MEM devices has been analyzed under different electrical signals and their possible applications in multiband/passband MEM filters/oscillators is discussed. Switching speed is a serious constraint for capacitive based RF-MEM switches. We have shown that a DC bias along with an ac bias at the resonant frequency can give very fast switching at a considerably less peak power requirement.

VHF single crystal silicon capacitive elliptic bulk-mode disk resonators-part II: implementation and characterization

Abstract: This work, the second of two parts, reports on the implementation and characterization of high-quality factor (Q) side-supported single crystal silicon (SCS) disk resonators. The resonators are fabricated on SOI substrates using a HARPSS-based fabrication process and are 3 to 18 /spl mu/m thick. They consist of a single crystal silicon resonant disk structure and trench-refilled polysilicon drive and sense electrodes. The fabricated resonators have self-aligned, ultra-narrow capacitive gaps in the order of 100 nm. Quality factors of up to 46 000 in 100 mTorr vacuum and 26000 at atmospheric pressure are exhibited by 18 /spl mu/m thick SCS disk resonators of 30 /spl mu/m in diameter, operating in their elliptical bulk-mode at /spl sim/150 MHz. Motional resistance as low as 43.3 k/spl Omega/ was measured for an 18-/spl mu/m-thick resonator with 160 nm capacitive gaps at 149.3 MHz. The measured electrostatic frequency tuning of a 3-/spl mu/m-thick device with 120 nm capacitive gaps shows a tuning slope of -2.6 ppm/V. The temperature coefficient of frequency for this resonator is also measured to be -26 ppm//spl deg/C in the temperature range from 20 to 150/spl deg/C. The measurement results coincide with the electromechanical modeling presented in Part I.

Capacitive proximity switch

Abstract: A capacitive proximity switch for detecting the change in the capacitance relative to a setpoint capacitance by the approach or retreat of an object in the sensitive area of a proximity switch, especially for use in the door handle of a motor vehicle, provides reliable error detection and error suppression at a fundamentally high sensitivity of the capacitive proximity switch by utilizing an evaluation unit that evaluates a measured value of the change in capacitance over time and depending on the time behavior of the measured value activates changes the operating threshold from a first threshold (which can be caused by a false object coming into or out of the sensitive area of the proximity switch) to a higher second threshold which can be reached only at a relatively greater change in capacitance caused by a target object coming into or out of the sensitive area of the proximity switch.

Low temperature fabrication of immersion capacitive micromachined ultrasonic transducers on silicon and dielectric substrates

Abstract: A maximum processing temperature of 250/spl deg/C is used to fabricate capacitive micromachined ultrasonic transducers (CMUTs) on silicon and quartz substrates for immersion applications. Fabrication on silicon provides a means for electronics integration via post-complementary metal oxide semiconductor (CMOS) processing without sacrificing device performance. Fabrication on quartz reduces parasitic capacitance and allows the use of optical displacement detection methods for CMUTs. The simple, low-temperature process uses metals both as the sacrificial layer for improved dimensional control, and as the bottom electrode for good electrical conductivity and optical reflectivity. This, combined with local sealing of the vacuum cavity by plasma-enhanced chemical-vapor deposition of silicon nitride, provides excellent control of lateral and vertical dimensions of the CMUTs for optimal device performance. In this paper, the fabrication process is described in detail, including process recipes and material characterization results. The CMUTs fabricated for intravascular ultrasound (IVUS) imaging in the 10-20 MHz range and interdigital CMUTs for microfluidic applications in the 5-20 MHz range are presented as device examples. Intra-array and wafer-to-wafer process uniformity is evaluated via electrical impedance measurements on 64-element ring annular IVUS imaging arrays fabricated on silicon and quartz wafers. The resonance frequency in air and collapse voltage variations are measured to be within 1% and 5%, respectively, for both cases. Acoustic pressure and pulse echo measurements also have been performed on 128 /spl mu/m/spl times/32 /spl mu/m IVUS array elements in water, which reveal a performance suitable for forward-looking IVUS imaging at about 16 MHz.

In situ processing of hydrocarbon-bearing formations with variable frequency automated capacitive radio frequency dielectric heating

Abstract: A hydrocarbon bearing formation which is heated using a variable frequency automated capacitive radio frequency dielectric heating in situ process. Hydrocarbons or other substances natural to a hydrocarbonaceous formation may be produced by heating specific chemical compositions with or without the use of a carrier medium. Separation of desired hydrocarbons from less sought-after constituents can occur in carrier medium subterranean reservoir. Hydrocarbon media can be slurry heated using a variable frequency automated capacitive radio frequency dielectric heating method. Slurry heated hydrocarbon media can be ejected to lower depths of carrier medium reservoir to impart hydrostatic pressure onto media. Hydraulic pressure blasted at cavern wall with carrier medium fluid possessing variable frequency automated capacitive radio frequency dielectric heating properties will be used to enlarge cavern size. Explosives can be used to enlarge cavern outer perimeter. The rubble from the hydraulic digging and/or explosion(s) will deposit hydrocarbonaceous substances in cavern carrier medium reservoir for heating and extraction of desired hydrocarbons. Remote vessels can be used in cavern reservoir to direct heating frequencies, for hydraulic mining, and/or for re-circulating carrier medium.

VHF single-crystal silicon elliptic bulk-mode capacitive disk resonators-part I: design and modeling

Abstract: This work, the first of two parts, presents the design and modeling of VHF single-crystal silicon (SCS) capacitive disk resonators operating in their elliptical bulk resonant mode. The disk resonators are modeled as circular thin-plates with free edge. A comprehensive derivation of the mode shapes and resonant frequencies of the in-plane vibrations of the disk structures is described using the two-dimensional (2-D) elastic theory. An equivalent mechanical model is extracted from the elliptic bulk-mode shape to predict the dynamic behavior of the disk resonators. Based on the mechanical model, the electromechanical coupling and equivalent electrical circuit parameters of the disk resonators are derived. Several considerations regarding the operation, performance, and temperature coefficient of frequency of these devices are further discussed. This model is verified in part II of this paper, which describes the implementation and characterization of the SCS capacitive disk resonators.

Piezoelectric passive distributed controllers for beam flexural vibrations

Abstract: Recent technological developments have made available efficient bender transducers based on the piezoelectric effect. In this paper an electrical circuit analog to the Timoshenko beam is synthesized using a Lagrangian method and by paralleling capacitive flux linkages to rotation and transverse displacement. A Piezo-ElectroMechanical (PEM) beam is conceived by uniformly distributing piezoelectric transducers on a beam and interconnecting their electric terminals via the found analog circuit, completed with suitable resistors. The high performance features of the synthesized novel circuit include the following. (i) The circuit topology is extremely reduced, the used components are all but one two-terminal elements, and the only two-port network needed is an ideal transformer. (ii) One and the same dissipative circuit ensures a multiresonance coupling with the vibrating beam and the optimal electrical dissipation of mechanical vibrations energy. (iii) For a prototype of a PEM beam, the design of the analog ...

Position control of parallel-plate microactuators for probe-based data storage

Abstract: In this paper, we present the use of closed-loop voltage control to extend the travel range of a parallel-plate electrostatic microactuator beyond the pull-in limit. Controller design considers nonlinearities from both the parallel-plate actuator and the capacitive position sensor to ensure robust stability within the feedback loop. Desired transient response is achieved by a pre-filter added in front of the feedback loop to shape the input command. The microactuator is characterized by static and dynamic measurements, with a spring constant of 0.17 N/m, mechanical resonant frequency of 12.4 kHz, and effective damping ratio from 0.55 to 0.35 for gaps between 2.3 to 2.65 /spl mu/m. The minimum input-referred noise capacitance change is 0.5 aF//spl radic/Hz measured at a gap of 5.7 /spl mu/m, corresponding to a minimum input-referred noise displacement of 0.33 nm//spl radic/Hz. Measured closed-loop step response illustrates a maximum travel distance up to 60% of the initial gap, surpassing the static pull-in limit of one-third of the gap.

Capacitive sensor array for localization of bioparticles in CMOS lab-on-a-chip

Abstract: Fully-electronic detection of cells and microbeads is achieved on a 320x320 array of capacitive sensors in 0.35/spl mu/m 2P3M CMOS technology that also integrates particle actuation by dielectrophoresis. Particle-associated equivalent input capacitance variations larger than 0.42fF are measured with 39dB SNR. Output noise is /spl les/1.6mV, the resolution of the 12b ADC.

Voltage-tunable piezoelectrically-transduced single-crystal silicon micromechanical resonators

Abstract: This paper reports on a new class of high-Q single-crystal silicon (SCS) resonators that are piezoelectrically actuated and sensed, and have voltage-tunable center frequencies. The resonating element is made out of the SCS device layer of a SOI wafer. In a unique manner, piezoelectric transduction was integrated with capacitive fine-tuning of the resonator center frequencies to compensate for any process variations. Quality factor as high as 6200 was measured for the 1.7 MHz first resonance mode of a clamped–clamped beam resonator in 50 mTorr vacuum. Higher order modes of the fabricated resonators were also successfully actuated and demonstrated quality factors larger than 2000 (under vacuum) at frequencies approaching 17 MHz. A 6 kHz tuning range was measured for a 719 kHz resonator by applying a dc voltage in the range of 0–20 V.

Capacitive touch on/off control for an automatic residential faucet

Abstract: A capacitive touch-controlled automatic faucet comprises: a spout, a magnetically latching valve, a proximity sensor, a handle, a capacitive touch-control, and a logical control. The proximity sensor is sensitive to motion of objects within a detection zone of the proximity sensor. The handle determines a water flow rate and temperature. The capacitive touch-control is positioned in the spout and generates an output signal while the touch-control is in contact with a user. The logical control receives the output signal, and toggles the magnetically latching valve when the output signal begins and ends within a period of time less than a predetermined threshold, but does not toggle the magnetically latching valve when the output signal persists for a period longer than the predetermined threshold. The faucet has a manual mode, wherein the proximity sensor is inactive, and a hands-free mode, wherein water flow is toggled in response to the proximity sensor.

Linear position sensors : theory and application

Abstract: Preface 1 Sensor Definitions and Conventions 11 Is It a Sensor or a Transducer? 12 Position versus Displacement 13 Absolute or Incremental Reading 14 Contact or Contactless Sensing and Actuation 15 Linear and Angular Configurations 16 Application versus Sensor Technology 2 Specifications 21 About Position Sensor Specifications 22 Measuring Range 23 Zero and Span 24 Repeatability 25 Nonlinearity 26 Hysteresis 27 Calibrated Accuracy 28 Drift 29 What Does All This about Accuracy Mean to Me? 210 Temperature Effects 211 Response Time 212 Output Types 213 Shock and Vibration 214 EMI/EMC 215 Power Requirements 216 Intrinsic Safety, Explosion Proofing, and Purging 217 Reliability 3 Resistive Sensing 31 Resistive Position Transducers 32 Resistance 33 History of Resistive Linear Position Transducers 34 Linear Position Transducer Design 35 Resistive Element 36 Wiper 37 Linear Mechanics 38 Signal Conditioning 39 Advantages and Disadvantages 310 Performance Specifications 311 Typical Performance Specifications and Applications 4 Capacitive Sensing 41 Capacitive Position Transducers 42 Capacitance 43 Dielectric Constant 44 History of Capacitive Sensors 45 Capacitive Position Transducer Design 46 Electronic Circuits for Capacitive Transducers 47 Guard Electrodes 48 EMI/RFI 49 Typical Performance Specifications and Applications 5 Inductive Sensing 51 Inductive Position Transducers 52 Inductance 53 Permeability 54 History of Inductive Sensors 55 Inductive Position Transducer Design 56 Coil 57 Core 58 Signal Conditioning 59 Advantages 510 Typical Performance Specifications and Applications 6 The LVDT 61 LVDT Position Transducers 62 History of the LVDT 63 LVDT Position Transducer Design 64 Coils 65 Core 66 Carrier Frequency 67 Demodulation 68 Signal Conditioning 69 Advantages 610 Typical Performance Specifications and Applications 7 The Hall Effect 71 Hall Effect Transducers 72 The Hall Effect 73 History of the Hall Effect 74 Hall Effect Position Transducer Design 75 Hall Effect Element 76 Electronics 77 Linear Arrays 78 Advantages 79 Typical Performance Specifications and Applications 8 Magnetoresistive Sensing 81 Magnetoresistive Transducers 82 Magnetoresistance 83 History of Magnetoresistive Sensors 84 Magnetoresistive Position Transducer Design 85 Magnetoresistive Element 86 Linear Arrays 87 Electronics 88 Advantages 89 Typical Performance Specifications and Applications 9 Magnetostrictive Sensing 91 Magnetostrictive Transducers 92 Magnetostriction 93 History of Magnetostrictive Sensors 94 Magnetostrictive Position Transducer Design 95 Waveguide 96 Position Magnet 97 Pickup Devices 98 Damp 99 Electronics 910 Advantages 911 Typical Performance Specifications 912 Application 10 Encoders 101 Linear Encoders 102 History of Encoders 103 Construction 104 Absolute versus Incremental Encoders 105 Optical Encoders 106 Magnetic Encoders 107 Quadrature 108 Binary versus Gray Code 109 Electronics 1010 Advantages 1011 Typical Performance Specification and Applications References Index

Capacitor based force sensor

Abstract: The invention provides a novel capacitive device configured to detect differences in an applied force over a continuous range of applied force that includes zero force. The device includes first and second electrodes that are spaced apart at a predetermined distance from each other in a rest position. A measurable capacitance exists between the first and second electrodes. Structured elements having a predetermined maximum dimension are positioned in the device to control the predetermined distance between the first and second electrodes. An applied force to the device causes a change in the distance between the first and second electrodes and a related change in the capacitance that can be measured to determine information related to the applied force.

Initial observation and analysis of dielectric-charging effects on RF MEMS capacitive switches

Abstract: Capacitance voltage and RF-output characteristics of electrostatically actuated MEMS switches were measured under different control and stress voltages. It was found that positive voltage stress caused negative charging of the dielectric whereas negative voltage stress caused positive charging of the dielectric. This is consistent with the amphoteric nature of traps in the silicon oxynitride dielectric used for the switches. A hypothesis of charge injection in minutes and charge migration in milliseconds was proposed to explain real-time and nonsymmetrical drift of pull-down and hold-down voltages of the switches.

Energy harvester with adjustable resonant frequency

Abstract: The present subject matter discloses devices, systems, and methodologies for harvesting power from environmentally induced vibrations. Piezoelectric devices (24) and structures are disclosed that may be employed in combination with electromagnetic (100) or capacitive (92, 94) elements to enhance the power harvesting capabilities of the piezoelectric devices (24). The electromagnetic (100) and capacitive (92, 94) elements may be used to assist in maintaining system mechanical resonance in order to maximize energy harvesting capabilities. Power harvesting devices and systems in accordance with the subject technology may concurrently operate as sensors in motion sensitive applications thus providing self-powered monitoring capabilities.

Inductive and capacitive coupling balancing electrical connector

Abstract: A network cable jack includes a printed circuit board (PCB) for balancing both inductive and capacitive coupling. Using a PCB allows compact trace paths to be formed without significantly increasing manufacturing costs. By including on each trace path two distinct inductance zones separated by a neutral zone, significant gains in degrees of freedom are achieved for designing PCB trace patterns in which a pair of inductive coupling zones jointly offset the inductive coupling caused by a specification plug and the jack contacts, both in magnitude and phase angle. Further, using distinct inductance zones offers more freedom regarding the placement of capacitive plates for use in capacitance balancing as well as the placement of terminals and insulation displacement contacts. Although the magnitude of a capacitive coupling is determined by the length of the capacitor plates parallel to current carrying traces, the approach allows capacitive and inductive coupling to be balanced independently.

Tuning sensitivity and selectivity of complementary metal oxide semiconductor-based capacitive chemical microsensors.

Abstract: New details on selectivity and sensitivity of fully integrated CMOS-based capacitive chemical microsensor systems are revealed. These microsystems have been developed to detect volatile organics in ambient air and rely on polymeric sensitive layers. The sensitivity and selectivity changes induced by thickness variation of the sensitive polymer layer allow for tuning of the layer parameters to achieve desired sensor features. Cross-sensitivity to interfering agents can be drastically reduced, as is shown for two important cases: (a) rendering the capacitive sensor insensitive to a low-dielectric-constant analyte (lower than that of the polymer) and (b) reducing the influence of a high-dielectric-constant analyte, such as water, on the sensor response. The second case is of vital importance for capacitive sensors, since water is omnipresent and evokes large capacitive sensor signals. The thickness-induced selectivity is explained as a combination of dielectric constant change and swelling and has been conf...

An in-plane high-sensitivity, low-noise micro-g silicon accelerometer with CMOS readout circuitry

Abstract: A high-sensitivity, low-noise in-plane (lateral) capacitive silicon microaccelerometer utilizing a combined surface and bulk micromachining technology is reported. The accelerometer utilizes a 0.5-mm-thick, 2.4/spl times/1.0 mm/sup 2/ proof-mass and high aspect-ratio vertical polysilicon sensing electrodes fabricated using a trench refill process. The electrodes are separated from the proof-mass by a 1.1-/spl mu/m sensing gap formed using a sacrificial oxide layer. The measured device sensitivity is 5.6 pF/g. A CMOS readout circuit utilizing a switched-capacitor front-end /spl Sigma/-/spl Delta/ modulator operating at 1 MHz with chopper stabilization and correlated double sampling technique, can resolve a capacitance of 10 aF over a dynamic range of 120 dB in a 1 Hz BW. The measured input referred noise floor of the accelerometer-CMOS interface circuit is 1.6/spl mu/g//spl radic/Hz in atmosphere.