Showing papers on "Capacitive sensing published in 2005"

An energy-efficient charge recycling approach for a SAR converter with capacitive DAC

Abstract: A new method for switching the capacitors in the DAC capacitor array of a successive approximation register (SAR) ADC is presented. By splitting the MSB capacitor into b - 1 binary scaled sub-capacitors, the average switching energy of the array can be reduced by 37% compared to a conventional switching method. A formal solution of the switching energy in four different switching methods is included, and the equations are verified using HSPICE simulations of a 10b capacitor array in a 0.18 /spl mu/m CMOS process.

Capacitive micromachined ultrasonic transducers: fabrication technology

Abstract: Capacitive micromachined ultrasonic transducer (MUT) technology is a prime candidate for next generation imaging systems. Medical and underwater imaging and the nondestructive evaluation (NDE) societies have expressed growing interest in cMUTs over the years. Capacitive micromachined ultrasonic transducer technology is expected to make a strong impact on imaging technologies, especially volumetric imaging, and to appear in commercial products in the near future. This paper focuses on fabrication technologies for cMUTs and reviews and compares variations in the production processes. We have developed two main approaches to the fabrication of cMUTs: the sacrificial release process and the recently introduced wafer-bonding method. This paper gives a thorough review of the sacrificial release processes, and it describes the new wafer-bonding method in detail. Process variations are compared qualitatively and quantitatively whenever possible. Through these comparisons, it was concluded that wafer-bonded cMUT technology was superior in terms of process control, yield, and uniformity. Because the number of steps and consequent process time were reduced (from six-mask process to four-mask process), turn-around time was improved significantly.

Analysis and Design Principles of MEMS Devices

Abstract: Chapter 1. Introduction to MEMS devices Chapter 2. Basic mechanics of beam and diaphragm structures Chapter 3. Air Damping Chapter 4. Electrostatic Actuation Chapter 5. Capacitive Sensing and Effects of Electrical Excitation Chapter 6. Piezoresistive Sensing

High-Q UHF micromechanical radial-contour mode disk resonators

Abstract: A micromechanical, laterally vibrating disk resonator, fabricated via a technology combining polysilicon surface-micromachining and metal electroplating to attain submicron lateral capacitive gaps, has been demonstrated at frequencies as high as 829 MHz and with Q's as high as 23 000 at 193 MHz Furthermore, the resonators have been demonstrated operating in the first three radial contour modes, allowing a significant frequency increase without scaling the device, and a 193 MHz resonator has been shown operating at atmospheric pressure with a Q of 8,880, evidence that vacuum packaging is not necessary for many applications These results represent an important step toward reaching the frequencies required by the RF front-ends in wireless transceivers The geometric dimensions necessary to reach a given frequency are larger for this contour-mode than for the flexural-modes used by previous resonators This, coupled with its unprecedented Q value, makes this disk resonator a choice candidate for use in the IF and RF stages of future miniaturized transceivers Finally, a number of measurement techniques are demonstrated, including two electromechanical mixing techniques, and evaluated for their ability to measure the performance of sub-optimal (eg, insufficiently small capacitive gap, limited dc-bias), high-frequency, high-Q micromechanical resonators under conditions where parasitic effects could otherwise mask motional output currents [1051]

Interleaved electrodes for touch sensing

Abstract: A capacitive touch sensing system includes a touch surface and sets of substantially parallel electrodes arranged in relation to the touch surface. Each electrode set includes a primary electrode electrically connected to at least two sub-electrodes. The primary electrode is capable of producing greater capacitive coupling to a touch in proximity with the touch surface in relation to capacitive coupling of the at least two sub-electrodes. The sub-electrodes of the electrode sets are arranged in an interleaved pattern configured to increase an effective area of capacitive coupling associated with each electrode set.

A wireless microsystem for the remote sensing of pressure, temperature, and relative humidity

Abstract: This work presents a microsystem that utilizes inductive power and data transfer through a backscatter-modulated carrier and a transducer interface that monitors its environment through embedded capacitive transducers. Formed on a single chip, transducers for temperature, pressure, and relative humidity are realized using a silicon-on-glass process that combines anodic bonding and a silicon-gold eutectic to realize vacuum-sealed cavities with low-impedance (6 /spl Omega/) electrical feedthroughs. Temperature is sensed capacitively using a row of Si/Au bimorph beams that produce a sensitivity of 15 fF//spl deg/C from 20 to 100/spl deg/C. The absolute pressure sensors have a sensitivity of 15 fF/torr and a range from 500 to 1200 torr, while the relative humidity sensor responds with 39 fF/%RH from 20 to 95%RH. A relaxation oscillator implements low-power capacitance-to-frequency conversion on a second chip with a sensitivity of 750 Hz/pF at 10 kHz, forming a 341 /spl mu/W transducer interface. The system is remotely powered by a 3-MHz carrier and has a volume of 32 mm/sup 3/, including the hybrid antenna wound around the perimeter of the system.

One layer capacitive sensing apparatus having varying width sensing elements

Abstract: One embodiment in accordance with the invention includes a two- dimensional capacitive sensor apparatus. The two-dimensional capacitive sensor can include a first sensing element having varying width, a second sensing element having varying width, and a third sensing element having varying width. Additionally, the first sensing element, second sensing element, and third sensing element are substantially parallel to a first axis. Furthermore, each of the first sensing element, second sensing element, and third sensing element can be located such that they are not required to overlap each other to determine a first location along the first axis of a two-dimensional space. Moreover, the first sensing element, second sensing element, and third sensing element can have a cumulative width that is substantially constant.

A method of increasing the spatial resolution of touch sensitive devices

Abstract: Disclosed herein is a capacitive touch sensitive device. One aspect of the touch sensitive device described herein is a reduction in the number of sensor circuits needed for circular or linear capacitive touch sensitive devices while maintaining the same resolution and absolute position determination for a single object. A related aspect of the touch sensitive device described herein a coding pattern that allows each sensor circuit of a capacitive touch sensitive device to share multiple electrodes at specially chosen locations in a sensor array such that the ability to determine the absolute position of a single object over the array is not compromised.

Lifetime characterization of capacitive RF MEMS switches

Abstract: RF MEMS switches provide a low-cost, high performance solution to many RF/microwave applications and these switches will be important building blocks for designing phase shifters, switched filters and reflector array antennas for military and commercial markets. In this paper, progress in characterizing of THALES capacitive MEMS devices under high RF power is presented. The design, fabrication and testing of capacitive RF MEMS switches for microwave/mm- wave applications on high-resistivity silicon substrate is presented. The switches tested demonstrated power handling capabilities of 1W (30 dbm) for continuous RF power. The reliability of these switches was tested at various power levels indicating that under continuous RF power. In addition a description of the power failures and their associated operating conditions is presented. The PC-based test stations to cycle switches and measure lifetime under DC and RF loads have been developed. Best-case lifetimes of 1010 cycles have been achieved in several switches from different lots under 30 dbm RF power.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Linear and nonlinear equivalent circuit modeling of CMUTs

Abstract: Using piston radiator and plate capacitance theory capacitive micromachined ultrasound transducers (CMUT) membrane cells can be described by one-dimensional (1-D) model parameters. This paper describes in detail a new method, which derives a 1-D model for CMUT arrays from finite-element methods (FEM) simulations. A few static and harmonic FEM analyses of a single CMUT membrane cell are sufficient to derive the mechanical and electrical parameters of an equivalent piston as the moving part of the cell area. For an array of parallel-driven cells, the acoustic parameters are derived as a complex mechanical fluid impedance, depending on the membrane shape form. As a main advantage, the nonlinear behavior of the CMUT can be investigated much easier and faster compared to FEM simulations, e.g., for a design of the maximum applicable voltage depending on the input signal. The 1-D parameter model allows an easy description of the CMUT behavior in air and fluids and simplifies the investigation of wave propagation within the connecting fluid represented by FEM or transmission line matrix (TLM) models.

Ion energy distribution control in single and dual frequency capacitive plasma sources

Abstract: Particle-in-cell/Monte Carlo simulations are used to study the possibility of ion energy distribution function (IEDF) control on the powered electrode in asymmetric single and double frequency capacitive discharges in argon. The possibility of IEDF control is demonstrated. It is shown that the IEDF shape and spread on the cathode can be controlled by the driven voltage in a single frequency discharge and by the low frequency voltage in a dual frequency capacitive discharge. It is shown that the IEDF shape on the powered electrode can be controlled by the driven frequency in single frequency capacitively coupled plasmas. It is shown that the density of plasma decreases, and the sheath width, the plasma potential and the self-bias voltage increase, with growth of the low frequency voltage in the dual frequency capacitive discharge.

Pixel circuit, display and driving method thereof

Abstract: The invention provides a pixel circuit that can cancel the influence of the mobility of a drive transistor. A drive transistor supplies a light-emitting element with an output current dependent upon an input voltage. The light-emitting element emits light with a luminance dependent upon a video signal in response to the output current supplied from the drive transistor. The pixel circuit includes a correction unit that corrects the input voltage held by a capacitive part in order to cancel the dependence of the output current on the carrier mobility.

Capacitive sensing apparatus having varying depth sensing elements

Abstract: One embodiment in accordance with the invention includes a capacitive sensor apparatus that includes a first sensing element having substantially constant width along its length and configured to have varying capacitive coupling to an object proximate to a capacitive sensing reference surface, along a first axis of the capacitive sensing reference surface. The length of the first sensing element is oriented along the first axis. The capacitive sensor apparatus can include a second sensing element having substantially constant width along its length and configured to have varying capacitive coupling to the object proximate to the capacitive sensing reference surface along the first axis. The length of the second sensing element is oriented along the first axis. The first and second sensing elements are conductive, and are configured to provide information corresponding to a spatial location of the object relative to the first axis of the capacitive sensing reference surface.

Review of Radar Absorbing Materials

Abstract: : Radar is a sensitive detection tool and since its development, methods for reducing microwave reflections have been explored. Radar absorbers can be classified as impedance matching or resonant absorbers. Radar absorbing materials are made from resistive and/or magnetic materials. Circuit analog materials give more design freedom through access to capacitive and inductive loss mechanisms. Dynamic absorbers can tune the absorption frequency through control of resistive and capacitive terms. Many conductive and magnetic materials have been trialed for absorption including carbon, metals and conducting polymers.

Vessel sealing system using capacitive RF dielectric heating

Abstract: An electrosurgical system for sealing vessels using capacitive (RF) dielectric heating and a method thereof are provided The system includes an electrosurgical instrument having an end effector with parallel plate electrodes that will clamp onto a vessel and maintain a specified gap distance; however, the electrodes will be coated with a non-conductive dielectric material Such an end effector will ensure that direct conduction between the electrodes does not occur through tissue or fluids and effectively creates a parallel plate capacitor with a dielectric, eg, tissue and coating, in between the plates The electrosurgical instrument will be activated with an AC signal at a specified RF frequency, eg, a Debye resonance frequency, via an electrosurgical generator An effective AC current will flow through the tissue and cause heating due to fictional losses from rotating polar molecules in the tissue

Modeling and characterization of dielectric-charging effects in RF MEMS capacitive switches

Abstract: For the first time, charging and discharging of traps in the dielectric of state-of-the-art RF MEMS capacitive switches were characterized in detail. Densities and time constants of different trap species were extracted under different control voltages. It was found that, while charging and discharging time constants are relatively independent of control voltage, steady-state charge densities increase exponentially with control voltage. A simple charge model was constructed to predict the amount of charge injected into the dielectric and the corresponding shift in actuation voltage. Good agreement was obtained between the model prediction and experimental data.

Modeling the capacitive nonlinearity in thin-film BST varactors

Abstract: A simple closed-form expression for the dielectric nonlinearity in thin-film high-permittivity barium strontium titanate (BST) devices is obtained from a third-order power-series expansion for the field-polarization relation. The expression is parameterized in terms of easily measurable quantities of zero-field capacitance and tuning ratio, and compares favorably with data on several representative BST compositions and device sizes. The temperature dependence of the capacitors is treated using a simple linear temperature coefficient in the zero-field capacitance that also compares favorably with experimental data on BST capacitors. The influence of interfacial ("dead" layer), fringing, and parasitic shunt capacitance on the experimental C-V curves is discussed. The results are potentially useful for circuit and electromagnetic simulation.

Temperature study of the dielectric polarization effects of capacitive RF MEMS switches

Abstract: This paper investigates both theoretically and experimentally the dielectric charging effects of capacitive RF microelectromechanical system switches with silicon nitride as dielectric layer. Dielectric charging caused by charge injection under voltage stress was observed. The amphoteric nature of traps and its effect on the switch operation were confirmed under both positive and negative control voltages. It has been confirmed that charging is a complicated process, which can be better described through the stretched exponential relaxation. This mechanism is thermally activated with an activation energy being calculated from the temperature dependence of the capacitance transient response. The charging mechanism, which is responsible for the pull-out voltage and the device failure, is also responsible for the temperature-induced shift of the capacitance minimum bias.

Reliability modeling of capacitive RF MEMS

Abstract: The kinetic of dielectric charging in capacitive RF microelectromechanical systems (RF MEMS) is investigated using an original method of stress and monitoring. This effect is investigated through a new parameter: the shift rate of the actuation voltages. We demonstrate that this lifetime parameter has to be considered as a function of the applied voltage normalized by the contact quality between the bridge and the dielectric. We also demonstrate that this phenomenon is related to Frenkel-Poole conduction, which takes place into the dielectric. We finally propose a model that describes the dielectric charging kinetic in capacitive RF MEMS. This model is used to extract a figure-of-merit of capacitive switches lifetime.

A novel capacitive pressure sensor based on sandwich structures

Abstract: This paper presents a sandwich structure for a capacitive pressure sensor. The sensor was fabricated by a simple three-mask process and sealed in vacuum by anodic bonding. The sensor, which utilizes a combined SiO/sub 2//Si/sub 3/N/sub 4/ layers as the elastic dielectric layers, exhibits high sensitivity. Mechanical characteristics of the sensor are theoretically analyzed based on a composite membrane theory and evaluated by use of finite element analysis (FEA). Square membrane sensors with side lengths of 800 /spl mu/m, 1000 /spl mu/m, 1200 /spl mu/m, and 1500 /spl mu/m were fabricated, providing a measured sensitivity of 0.08 pF/kPa, 0.12 pF/kPa, 0.15 pF/kPa, and 0.2 pF/kPa, respectively. The nonlinearity of the sensor is less than 1.2% over a dynamic range 80-106 kPa and the maximum hysteresis is about 3.3% to the full scale capacitance change. The TCO at 101 kPa is 1923 ppm//spl deg/C. All the electrodes of the sensor are leaded from the top side of the chip. Residual pressure in the sealed cavity at room temperature is evaluated by a pressure scanning test, indicating about 8 kPa. Comparison of experimental results with theoretical analysis shows that change of capacitance for the sandwich structure under pressure is mainly due to variation of the dielectric constant while geometric variations such as the area change of electrodes and the thickness change of dielectric layers is about two orders less than the variation of the dielectric constant. Sensitivity enhancements for the sensor are qualitatively discussed based on the physical effects of strained dielectrics, including electrostriction and flexoelectricity. [1551].

Fully-differential poly-SiC Lame mode resonator and checkerboard filter

Abstract: In this paper, we report the first fully-differential, electrostatically transduced RF MEMS resonator. The fully-differential electrode configuration not only cancels capacitive feedthrough between the drive and sense terminals but also eliminates the reduction in electromechanical quality factor (Q) from the large ohmic resistance of the polycrystalline silicon carbide (poly-SiC) suspension and anchor. Using this configuration, we have demonstrated a 173 MHz poly-SiC Lame-mode resonator with a Q of 9,300 in air. By mechanically coupling five Lame-mode resonators into a 2-D checkerboard, we have realized a 173 MHz center frequency band-pass filter with 110 kHz bandwidth and < 2 dB pass-band ripple.

Phase noise in capacitively coupled micromechanical oscillators

Abstract: Phase noise in capacitively coupled micro-resonator-based oscillators is investigated. A detailed analysis of noise mixing mechanisms in the resonator is presented, and the capacitive transduction is shown to be the dominant mechanism for low-frequency 1/f-noise mixing into the carrier sidebands. Thus, the capacitively coupled micromechanical resonators are expected to be more prone to the 1/f-noise aliasing than piezoelectrically coupled resonators. The analytical work is complemented with simulations, and a highly efficient and accurate simulation method for a quantitative noise analysis in closed-loop oscillator applications is presented. Measured phase noise for a microresonator-based oscillator is found to agree with the developed analytical and simulated noise models.

Direct observation of Josephson capacitance

Abstract: The effective capacitance has been measured in the split Cooper-pair box (CPB) over its phase-gate bias plane. Our low-frequency reactive measurement scheme allows us to probe purely the capacitive susceptibility due to the CPB band structure. The data are quantitatively explained using parameters determined independently by spectroscopic means. In addition, we show in practice that the method offers an efficient way to do nondemolition readout of the CPB quantum state.

Vibrating micromechanical resonators with solid dielectric capacitive transducer gaps

Abstract: VHF and UHF MEMS-based vibrating micromechanical resonators equipped with new solid dielectric (i.e., filled) capacitive transducer gaps to replace previously used air gaps have been demonstrated at 160 MHz, with Q's ~ 20,200 on par with those of air-gap resonators, and motional resistances (Rx's) more than 8times smaller at similar frequencies and bias conditions. This degree of motional resistance reduction comes about via not only the higher dielectric constant provided by a solid-filled electrode-to-resonator gap, but also by the ability to achieve smaller solid gaps than air gaps. These advantages with the right dielectric material may now allow capacitively-transduced resonators to match to the 50-377 Omega impedances expected by off-chip components (e.g., antennas) in many wireless applications without the need for high voltages. In addition to lower motional resistance, the use of filled-dielectric transducer gaps provides numerous other benefits over the air gap variety, since it (a) better stabilizes the resonator structure against shock and microphonics; (b) eliminates the possibility of particles getting into an electrode-to-resonator air gap, which poses a potential reliability issue; (c) greatly improves fabrication yield, by eliminating the difficult sacrificial release step needed for air gap devices; and (d) potentially allows larger micromechanical circuits (e.g., bandpass filters comprised of interlinked resonators) by stabilizing constituent resonators as the circuits they comprise grow in complexity

Sensor system and methods for the capacitive measurement of electromagnetic signals having a biological origin

Abstract: The invention relates to a sensor system and several method for the capacitive measurement of electromagnetic signals having a biological origin. Such a sensor system comprises a capacitive electrode device (10), an electrode shielding element (20) which surrounds the electrode device (10) at least in part in order to shield the same (10) from interfering external electromagnetic fields, and a signal processing device (30) for processing electromagnetic signals that can be detected by means of the electrode device (10). According to the invention, additional shielding means (21) three-dimensionally surround the electrode device (10) and the electrode shielding element (20) at least in part in order to block out interfering external electromagnetic fields. The changes in the electrode capacity of the capacitive sensor system are determined with the aid of several methods which particularly use the inventive sensor system in order to take said changes into account when the test signals are evaluated.

Gap-change sensing through capacitive techniques

Abstract: A gap-change sensing through capacitive techniques is disclosed. In one embodiment, an apparatus includes a first conductive surface (320) and a second conductive surface (322) substantially parallel to the first conductive surface, and a sensor to generate a measurement based on a change in a distance between the first conductive surface and the second conductive surface. The change in the distance may be caused by a deflection of the first conductive surface with respect to the second conductive surface, and the deflection may be a compressive force and/or an expansive force. The sensor may apply an algorithm that converts a change in capacitance to at least one of a change in voltage and/or a change in frequency to generate the measurement. The change in the distance may be caused a load applied to the surface above the first conductive surface with respect to the second conductive surface.

Micro-gravity capacitive silicon-on-insulator accelerometers

Abstract: In this paper, the implementation and characterization of high-sensitivity in-plane capacitive micro-gravity silicon-on-insulator (SOI) accelerometers with the readout circuitry are presented The devices were implemented in 50 µm thick SOI substrates using a two-mask dry-release process The fabricated accelerometers were interfaced to a low-noise low-power reference-capacitor-less switched-capacitor circuit The integrated circuit (IC) was implemented in a 25 V 025 N-well CMOS process The measured capacitive sensitivity is 03 pF g−1, equivalent to a gain of 075 V g−1 The measured resolution is 11 µg Hz−1/2 at 2 Hz and 02 µg Hz−1/2 at 100 Hz (resolution bandwidth = 1 Hz) The interface IC operates from a single 25 V supply and measures a power consumption of 4 mW with a sampling clock of 100 kHz The core IC die size is 065 mm2

Pixel circuit, display device, and driving method therefor

Abstract: PROBLEM TO BE SOLVED: To provide a pixel circuit capable of canceling the influence of mobility of a drive transistor. SOLUTION: The drive transistor Trd supplies an output current to a light emitting element EL according to an input voltage Vgs for a predetermined light emitting period. The light emitting element EL emit light with brightness proportional to a video signal by the output current supplied from the drive transistor Trd. To offset dependency on the carrier mobility of the output current, the pixel circuit is provided with a correction means for correcting the input voltage Vgs pre-held by a capacitive part Cs before or at the head of the light emitting period. This correction means operates in a part of a sampling period according to the control signals supplied from scanning lines DS, WS, AZ1, and AZ2, and takes out the output current from the drive transistor Trd in the state in which the video signal is being sampled, and negatively feeds back the output current to the capacitive part Cs to correct the input voltage Vgs. COPYRIGHT: (C)2006,JPO&NCIPI

Vibration Control of Beams with Negative Capacitive Shunting of Interdigital Electrode Piezoceramics

Abstract: A pair of interdigital electrode (IDE) piezoceramics is used to simultaneously suppress multimode vibrations of a cantilevered beam. This is achieved by connecting the IDE piezoceramics in parallel to a negative capacitive shunt circuit. The governing equations of motion of an IDE piezo/beam system and associated boundary conditions are derived using the Hamilton principle. The obtained mathematical model is validated experimentally Attenuations ranging between 5 and 20 dB are obtained for all the vibration modes over the frequency range of 0-3000 Hz. The presented theoretical and experimental techniques provide invaluable tools for designing simple and effective passive vibration dampers for structures with closely packed modes.