Showing papers on "Capacitive sensing published in 2006"

An untethered, electrostatic, globally controllable MEMS micro-robot

Abstract: We present an untethered, electrostatic, MEMS micro-robot, with dimensions of 60 /spl mu/m by 250 /spl mu/m by 10 /spl mu/m. The device consists of a curved, cantilevered steering arm, mounted on an untethered scratch drive actuator (USDA). These two components are fabricated monolithically from the same sheet of conductive polysilicon, and receive a common power and control signal through a capacitive coupling with an underlying electrical grid. All locations on the grid receive the same power and control signal, so that the devices can be operated without knowledge of their position on the substrate. Individual control of the component actuators provides two distinct motion gaits (forward motion and turning), which together allow full coverage of a planar workspace. These MEMS micro-robots demonstrate turning error of less than 3.7/spl deg//mm during forward motion, turn with radii as small as 176 /spl mu/m, and achieve speeds of over 200 /spl mu/m/sec with an average step size as small as 12 nm. They have been shown to operate open-loop for distances exceeding 35 cm without failure, and can be controlled through teleoperation to navigate complex paths. The devices were fabricated through a multiuser surface micromachining process, and were postprocessed to add a patterned layer of tensile chromium, which curls the steering arms upward. After sacrificial release, the devices were transferred with a vacuum microprobe to the electrical grid for testing. This grid consists of a silicon substrate coated with 13-/spl mu/m microfabricated electrodes, arranged in an interdigitated fashion with 2-/spl mu/m spaces. The electrodes are insulated by a layer of electron-beam-evaporated zirconium dioxide, so that devices placed on top of the electrodes will experience an electrostatic force in response to an applied voltage. Control waveforms are broadcast to the device through the capacitive power coupling, and are decoded by the electromechanical response of the device body. Hysteresis in the system allows on-board storage of n=2 bits of state information in response to these electrical signals. The presence of on-board state information within the device itself allows each of the two device subsystems (USDA and steering arm) to be individually addressed and controlled. We describe this communication and control strategy and show necessary and sufficient conditions for voltage-selective actuation of all 2/sup n/ system states, both for our devices (n=2), and for the more general case (where n is larger.).

Apparatus and method for reducing average scan rate to detect a conductive object on a sensing device

Abstract: A switch circuit and method is described. In one embodiment, the switch circuit is configured to couple each of a plurality of plurality of capacitive sense elements and a plurality of capacitance sensors in different modes. In a first mode, the switch circuit is configured to couple each of the plurality of capacitance sensors to a group of two or more of the plurality of capacitive sense elements. In a second mode, the switch circuit is configured to couple the plurality of capacitance sensors to individual ones of the two or more of the plurality of capacitive sense elements in one of the groups.

Noise analysis and characterization of a sigma-delta capacitive microaccelerometer

Abstract: This paper reports a high-sensitivity low-noise capacitive accelerometer system with one micro-g//spl radic/Hz resolution. The accelerometer and interface electronics together operate as a second-order electromechanical sigma-delta modulator. A detailed noise analysis of electromechanical sigma-delta capacitive accelerometers with a final goal of achieving sub-/spl mu/g resolution is also presented. The analysis and test results have shown that amplifier thermal and sensor charging reference voltage noises are dominant in open-loop mode of operation. For closed-loop mode of operation, mass-residual motion is the dominant noise source at low sampling frequencies. By increasing the sampling frequency, both open-loop and closed-loop overall noise can be reduced significantly. The interface circuit has more than 120 dB dynamic range and can resolve better than 10 aF. The complete module operates from a single 5-V supply and has a measured sensitivity of 960 mV/g with a noise floor of 1.08 /spl mu/g//spl radic/Hz in open-loop. This system can resolve better than 10 /spl mu/g//spl radic/Hz in closed-loop.

Detection of and compensation for stray capacitance in capacitive touch sensors

Abstract: The present invention provides systems and methods for detecting stray capacitance in capacitive touch sensors. The existence of stray capacitance can lead to errors in touch detection and touch position determination. Such errors can be avoided or corrected when the stray capacitance is detected. Detecting stray capacitance includes analyzing signals for features characteristic of stray capacitance noise events. Such features can include spatial features such as the location of a test touch position determined from signals caused by stray capacitance, as well as temporal features such as the rate of change of the detected signals.

Semiconductor device and manufacturing method thereof

Abstract: PROBLEM TO BE SOLVED: To mount a capacitive element constituted of polycrystalline silicon on the same substrate together with a high breakdown voltage transistor, while contriving the simplification of the manufacturing process therefor. SOLUTION: After forming a gate insulating film 7 on a high breakdown voltage transistor forming region R1 of the semiconductor substrate 1 by effecting the thermal oxidation of surface of the semiconductor substrate 1 employing an oxidation preventing film 6 as a mask, an oxidation preventing film 6 on the low breakdown voltage transistor forming region R2 is removed and, further, the thermal oxidation of surface of the semiconductor substrate 1 is effected employing the oxidation preventing film 6 as the mask. Accordingly, a gate insulating film 7 on a high breakdown voltage transistor forming region R1 is thickened and a gate insulating film 8 is formed on the semiconductor substrate 1 in the low breakdown voltage transistor forming region R2 while forming an upper electrode 9c, arranged through the oxidation preventing film 6, in one region on the lower electrode 4. COPYRIGHT: (C)2007,JPO&INPIT

Piezoelectric Active Sensor Self-Diagnostics Using Electrical Admittance Measurements

Abstract: This paper presents a piezoelectric sensor self-diagnostic procedure that performs in situ monitoring of the operational status of piezoelectric materials used for sensors and actuators in structural health monitoring (SHM) applications. The sensor/actuator self-diagnostic procedure, where the sensors/actuators are confirmed to be functioning properly during operation, is a critical component to successfully complete the SHM process with large numbers of active sensors typically installed in a structure. The premise of this procedure is to track the changes in the capacitive value of piezoelectric materials resulting from the degradation of the mechanical/electrical properties and its attachment to a host structure, which is manifested in the imaginary part of the measured electrical admittances. This paper concludes with an experimental example to demonstrate the feasibility of the proposed procedure.

Single-layer capacitive sensing device

Abstract: A touch-sensor device, and method of making same, having a sensor element, conductive sensor trace, and active electronic components disposed on a single-layer.

MEMS based hair flow-sensors as model systems for acoustic perception studies

Abstract: Arrays of MEMS fabricated flow sensors inspired by the acoustic flow-sensitive hairs found on the cerci of crickets, have been designed, fabricated and characterized. The hairs consist of up to 1 mm long SU-8 structures mounted on suspended membranes with normal translational and rotational degrees of freedom. Electrodes on the membrane and on the substrate form variable capacitors allowing for capacitive read-out. Capacitance versus voltage, frequency dependency and directional sensitivity measurements have been successfully carried out on fabricated sensor arrays, showing the viability of the concept. The sensors form a model-system allowing for investigations on sensory acoustics by their arrayed nature, their adaptivity via electrostatic interaction (frequency tuning and parametric amplifica- tion) and their susceptibility to noise (stochastic resonance)

Modeling and analysis of crosstalk noise in coupled RLC interconnects

Abstract: At current operating frequencies, inductive-coupling effects can be significant and should be included for accurate crosstalk-noise analysis. In this paper, an analytical framework to model crosstalk noise in coupled RLC interconnects is presented. The proposed model is based on transmission-line theory and captures high-frequency effects in on-chip interconnects. The new model is generic in nature and can be applied to asymmetric driver-and-line configurations for aggressor and victim wires. The model is compared against SPICE simulations and is shown to capture both the waveform shape and peak noise accurately. Over a large set of random test cases, the average error in noise-peak estimation is approximately 6.5%. A key feature of the new model is that its derivation and form enables physical insight into the total coupling-noise-waveform shape and its dependence on relevant physical-design parameters. Due to its simplicity and physical nature, the proposed model can be applied to investigate the impact of various physical-design optimizations (e.g., wire sizing and spacing, shield insertion) on total RLC coupled noise. The effectiveness of various existing noise-reduction techniques in the presence of mutual-inductance coupling is studied here. The obtained results indicate that common (capacitive) noise-avoidance techniques can behave quite differently when both capacitive and inductive coupling are considered together.

An Analysis of Latch Comparator Offset Due to Load Capacitor Mismatch

Abstract: This brief analyzes the effect of load capacitor mismatch on the offset of a regenerative latch comparator. Two analytical models are presented and compared with HSpice simulations. Our results indicate that in a typical 0.18-mum CMOS latch, a capacitive imbalance of only 1 fF can lead to offsets of several tens of millivolts

Headsets and headset power management

Abstract: The invention relates to an energy saving headset that comprises a power management unit operable to reduce the power consumption of the headset when a user is not present. The power management unit uses capacitive sensing to detect the presence of the user. Capacitive sensing is advantageous since it provides a flexible and reliable sensor that can accurately detect the presence or absence of a user either by detecting user proximity or user contact. Moreover, in various embodiments, the sensitivity of a capacitive sensor may be adjusted to account for user movement or changes in environmental conditions, such as, for example, the presence of water, or sweat, on the headset to further improve sensing reliability. The invention further relates to headsets using user presence signals based on capacitive sensing to control other functions of the headset or to control external devices to which the headset is connected, either wirelessly or by wires.

Collisionless heating in capacitive discharges enhanced by dual-frequency excitation.

Abstract: We discuss collisionless electron heating in capacitive discharges excited by a combination of two disparate frequencies. By developing an analytical model, we find, contrary to expectation, that the net heating in this case is much larger than the sum of the effects occurring when the two frequencies act separately. This prediction is substantiated by kinetic simulations, which are also in excellent general quantitative agreement with the model for discharge parameters that are typical of recent experiments.

Carbon nanotube-enhanced capillary condensation for a capacitive humidity sensor

Abstract: A capacitive humidity sensor is presented for moisture detection at room temperature. The sensor is fabricated by depositing multi-wall carbon nanotubes (MWCNTs) on one of the stainless-steel substrates. When compared to a sensor without CNTs, a CNT-enhanced sensor has an increase of 60-200% in capacitance response when the humidity is under 70% relative humidity (RH), and 300-3000% if the RH level goes over 70%. The performance is comparable to a commercial sensor from Honeywell, which is used as a benchmark throughout the experiments. Our results demonstrate that nano-materials like MWCNTs can naturally form networks of porous nano-structures, which can potentially realize a miniature capacitive humidity sensor with a higher sensitivity. The gain in performance is attributed to the capillary condensation effect.

Capacitive touch sense device having polygonal shaped sensor elements

Abstract: A touch sensor pad having polygon shaped sensor elements of five or more sides is described.

Flexible capacitive sensor

Abstract: The invention relates to a flexible, resilient capacitive sensor suitable for large-scale manufacturing. The sensor comprises a dielectric, an electrically conductive layer on the first side of the dielectric layer, an electrically conductive layer on a second side of the dielectric layer, and a capacitance meter electrically connected to the two conductive layers to detect changes in capacitance upon application of a force to the detector. The conductive layers are configured to determine the position of the applied force. The sensor may be shielded to reduce the effects of outside interference.

An Analytical Fringe Capacitance Model for Interconnects Using Conformal Mapping

Abstract: An analytical model is proposed to compute the fringe capacitance between two nonoverlapping interconnects in different layers using a conformal mapping technique. With this technique, electric field lines are geometrically approximated to separately model the different capacitive components. These components are finally combined to obtain the equivalent fringe capacitance. Using the aforementioned technique, a model was developed to compute the capacitances of typical interconnect geometries using technology-dependent parameters. The proposed model closely matches with FASTCAP results and significantly reduces the computational complexity and time in calculating the interconnect capacitances

Fundamentals of the capacitive resistivity technique

Abstract: Capacitive resistivity (CR) is an emerging geophysical technique designed to extend the scope of the conventional methodology of dc resistivity to environments where galvanic coupling is notoriously difficult to achieve — for example, across engineered structures (roads, pavements), hard rock, dry soil, or frozen ground. Conceptually, CR is based on a four-point array capacitively coupled to the ground. Under certain conditions, capacitive measurements of resistivity are equivalent to those obtained with the dc technique, thus making dc interpretation schemes applicable to CR data. The coupling properties of practical sensor realizations are shown to be a function of their geometrical arrangement. Separate bodies of theory are associated with two complementary but distinct sensor types: the capacitive-line antenna and the plate-wire combination. The use of plate-wire combinations results in localized coupling, which, in conjunction with a quasi-static (low-frequency) formulation of the transfer impedance,...

Temperature compensation method for capacitive sensors

Abstract: A method and apparatus for detecting an environmental effect and a presence of a conductive object on a touch-sensing device without using a dedicated environmental effect sensor, and compensating for the environmental effect on the detection of the conductive object. The method may include detecting an environmental effect on a touch-sensing device using a touch sensor, detecting a presence of a conductive object, and compensating for the environmental effect on the detection of the conductive object. The apparatus may include a touch-sensing device having a touch sensor to detect an environmental effect and a processing device to compensate for the environmental effect.

A capacitive RF power sensor based on MEMS technology

Abstract: Wideband 100 kHz–4 GHz power sensors are presented, which are based on sensing the electrostatic force between an RF signal line and a suspended membrane. The electrostatic force, which is proportional to the square of the rms signal voltage and thus to the signal power, results in a displacement of the suspended membrane. This displacement is detected capacitively, allowing the sensing of the signal power with extremely low dissipative losses; therefore the sensor can be placed in a transmission line with negligible disturbance of the signal. Devices have been designed and fabricated successfully by aluminum surface micromachining using photoresist as the sacrificial layer. Optimization of the design with SONNET has resulted in measured return and insertion losses (S11 and S21) better than -30 dB and -0.15 dB, respectively, up to 4 GHz, and a sensitivity of 90 aF mW-1.

MEMS-Capacitive Pressure Sensor Fabricated Using Printed-Circuit-Processing Techniques

Abstract: Microelectromechanical systems (MEMS)-based capacitive pressure sensors are typically fabricated using silicon-micromachining techniques. In this paper, a novel liquid-crystal polymer (LCP)-based MEMS-capacitive pressure sensor, fabricated using printed-circuit-processing technique, is reported. The pressure sensor consists of a cylindrical cavity formed by a sandwich of an LCP substrate, an LCP spacer layer with circular holes, and an LCP top layer. The bottom electrode and the top electrode of the capacitive pressure sensor are defined on the top side of the LCP substrate and the bottom side of the top-LCP layer, respectively. An example pressure sensor with a diaphragm radius of 1.6 mm provides a total capacitance change of 0.277 pF for an applied pressure in the range of 0-100 kPa

Parylene micro membrane capacitive sensor array for chemical and biological sensing

Abstract: The need for high-throughput label-free multiplexed sensors for chemical and biological sensing has increased tremendously in the last decade with new applications in the areas of genetics, diagnostics, drug discovery, as well as security and threat evaluation. Surface stress-based sensors are a relatively new class of sensors that has immense potential to satisfy the demand, and has been investigated extensively in the recent years. In this paper we present the design and fabrication of a novel parylene micro membrane surface stress sensor that exploits the low mechanical stiffness of polymers. The salient features of the sensor are that it: (i) is label-free; (ii) is a universal platform suitable for both chemical and biological sensing; (iii) uses electronic (capacitive detection) readout; (iv) has integrated microfluidics for addressing individual sensors on the chip; (v) is capable of handling both liquid and gas samples; (vi) is made using standard low temperature microfabrication processes (

Experimental characterization of collapse-mode CMUT operation

Abstract: This paper reports on the experimental characterization of collapse-mode operation of capacitive micromachined ultrasonic transducers (CMUTs). CMUTs are conventionally operated by applying a direct current (DC) bias voltage less than the collapse voltage of the membrane, so that the membrane is deflected toward the bottom electrode. In the conventional regime, there is no contact between the membrane and the substrate; the maximum alternating current (AC) displacement occurs at the center of the membrane. In collapse-mode operation, the DC bias voltage is first increased beyond the collapse voltage, then reduced without releasing the collapsed membrane. In collapse-mode operation, the center of the membrane is always in contact with the substrate. In the case of a circular membrane, the maximum AC displacement occurs along the ring formed between the center and the edge of the membrane. The experimental characterization presented in this paper includes impedance measurements in air, pulse-echo experiments in immersion, and one-way optical displacement measurements in immersion for both conventional and collapse-mode operations. A 205-mum times 205-mum 2-D CMUT array element composed of circular silicon nitride membranes is used in the experiments. In pulse-echo experiments, a custom integrated circuit (IC) comprising a pulse driver, a transmit/receive switch, a wideband low-noise preamplifier, and a line driver is used. By reducing the parasitic capacitance, the use of a custom IC enables pulse-echo measurements at high frequencies with a very small transducer. By comparing frequency response and efficiency of the transducer in conventional and collapse regimes, experimental results show that a collapsed membrane can be used to generate and detect ultrasound more efficiently than a membrane operated in the conventional mode. Furthermore, the center frequency of the collapsed membrane can be changed by varying the applied DC voltage. In this study, the center frequency of a collapsed transducer in immersion is shown to vary from 20 MHz to 28 MHz with applied DC bias; the same transducer operates at 10 MHz in the conventional mode. In conventional mode, the maximum peak-to-peak pressure is 370 kPa on the transducer surface for a 40-ns, 25-V unipolar pulse excitation. In collapse mode, a 25-ns, 25-V unipolar pulse generates 590 kPa pressure at the surface of the transducer

A low-cost noncontact capacitance-type level transducer for a conducting liquid

Abstract: In this paper, an attempt has been made to design a low-cost noncontact capacitance-type level sensor for a conducting liquid. The sensor is in the form of a uniform circular cylinder made of insulating material like glass, ceramic, plastic, etc. The sensor is connected with the metallic- or nonmetallic-type liquid storage tank, in which the conducting liquid column is taken as one electrode, and a noninductively wound short-circuited outside coil is taken as the other electrode of a variable capacitor. The change in capacitance due to the change of liquid level is measured by a modified linear operational-amplifier-based De' Sauty bridge network with adjustable bridge sensitivity. The bridge output after amplification and rectification may be used to drive a direct current indicator calibrated in level. The studies have been made with high-density polyethylene and glass tube sensors separately in both metallic and nonmetallic storage tanks with tap water as the conducting liquid, and the experimental results of the static characteristics of the level sensors with percentage error from linearity are presented in the paper. These results are found to have good linearity and repeatability within acceptable limits

Acceleration of Dielectric Charging in RF MEMS Capacitive Switches

Abstract: To design and validate accelerated life tests of RF MEMS capacitive switches, acceleration factors of charging effects in switch dielectric were quantitatively characterized. From measured charging and discharging transient currents at different temperatures and control voltages, densities and time constants of dielectric traps were extracted. A charging model was constructed to predict the amount of charge injected into the dielectric and the corresponding shift in actuation voltage under different acceleration factors such as temperature, peak voltage, duty factor, and frequency of the control waveform. Agreement was obtained between the model prediction and experimental data. It was found that temperature, peak voltage, and duty factor were critical acceleration factors for dielectric-charging effects whereas frequency had little effect on charging

Integrated Liquid Crystal Display and Touchscreen for an Electronic Device

Abstract: An integrated display for an electronic device, comprising: a liquid crystal display having a first polarizing layer coupled to a colour filter layer; and, a first transparent conductive material layer disposed between the first polarizing layer and the colour filter layer to thereby form a capacitive touchscreen sensor.

Capacitance Sensors for Void-Fraction Measurements and Flow-Pattern Identification in Air–Oil Two-Phase Flow

Abstract: The design methodology of capacitance sensors for void-fraction measurement in adiabatic two-phase flow systems is presented in this paper. The effect of design parameters on the capacitance output has been theoretically and experimentally investigated for two types of sensor configurations: concave and ring types. Experiments were performed using air-oil two-phase flow to determine the signal-to-noise ratio, sensitivity, and time response of the capacitance sensors. The results show that the ring-type sensors are more sensitive to the void-fraction signal than the concave type for the same spatial resolution. The predictions from the theoretical model for the ring-type sensors are in better agreement with the experimental results than for the concave type. The mean value, time trace, power spectral density (PSD), and the probability density function (PDF) of the void-fraction signal from the capacitance sensors are used to objectively identify the flow pattern. The method was validated using high-speed video images of the flow and comparing the results to those from the signal analysis

Versatile and compact capacitive dilatometer

Abstract: We describe the design, construction, calibration, and operation of a relatively simple differential capacitive dilatometer suitable for measurements of thermal expansion and magnetostriction from 300 to below 1K with a low-temperature resolution of about 0.05A. The design is characterized by an open architecture permitting measurements on small samples with a variety of shapes. Dilatometers of this design have operated successfully with a commercial physical property measurement system, with several types of cryogenic refrigeration systems, in vacuum, in helium exchange gas, and while immersed in liquid helium (magnetostriction only) to temperatures of 30mK and in magnetic fields to 45T.

Electromagnetic field nonuniformities in large area, high-frequency capacitive plasma reactors, including electrode asymmetry effects

Abstract: Electromagnetic wave propagation effects can give rise to important limitations for processing uniformity in large area, radio-frequency (rf) capacitive plasma reactors. The electromagnetic wavefield solution is derived for a capacitive, high-frequency, cylindrical reactor with symmetric or asymmetric electrode areas containing a uniform plasma slab. It is shown that only two distinct electromagnetic modes are necessary and sufficient to determine the electromagnetic fields everywhere within the reactor except close to the sidewalls. The first mode gives rise to the interelectrode rf voltage standing wave effect associated with high frequencies in large area reactors, and the second mode gives rise to the telegraph effect associated with asymmetric electrode areas, which necessitates the redistribution of rf current along the plasma to maintain rf current continuity. This work gives a unified treatment of both effects which have previously been studied separately, experimentally and theoretically, in the literature. The equivalent circuit of each mode is also derived from its respective dispersion relation. Examples of this electromagnetic wavefield solution show that both modes can cause nonuniformity of the plasma rf potential, depending on the reactor geometry, excitation frequency and plasma permittivity and sheath width, which has consequences for large-area plasma processing.

Dual-sided track pad

Abstract: A system including a capacitive array element capable of sensing touch from either side is described. A connected processor unit, either in the device or the host system, may be adapted to interpret signals from the capacitive array element as a cursor or view movement with six degrees of freedom. The track pad device may include a display element and the capacitive array element may be translucent. The display element and the array element may be configured with respect to each other, where different configurations can be associated with different operating modes. For example, when the array element lies over the display screen so that the display screen is viewable through the array element, the array element can function as a touch screen. In another configuration, the array element may generate signals indicating a user's touch from one or the other or both sides of the array element.

A High-Performance MEMS Capacitive Strain Sensing System

Abstract: This paper describes a high-performance strain sensing microsystem. The system consists of four parallel differential MEMS capacitive strain sensors with a nominal capacitance value of 440 fF, converting an input strain to a capacitance change with a sensitivity of 265 aF per microstrain (muepsiv), and low-noise integrated sensing electronics, which employ a differential continuous-time synchronous detection architecture converting the capacitive signal to an output voltage for further signal processing. Based on system noise characterization, the prototype design shows a capability of measuring a strain resolution of 0.9 nepsiv/radicHz, while demonstrating a maximum dc input stain range of 1000 muepsiv. The overall system consumes 1.5 mA dc current from a 3-V supply