Showing papers on "Rise time published in 2007"

A new approach to develop ionic polymer-metal composites (IPMC) actuator: Fabrication and control for active catheter systems

Abstract: The ionic polymer–metal composite (IPMC) is one type of electro-active materials with the characteristics of low electric driving potential, large deformation and aquatic manipulation. It is highly attractive to biomedical applications as an actuator or a sensor. The main purpose of this study was to develop an IPMC actuator for active catheter systems. The first step was to develop a low cost and high reliability fabrication procedure to yield an IPMC actuator. In the second step, the dynamic behavior of the actuator was tested in an aqueous environment. An empirical model was then constructed, which consisted of a fourth-order linear system, a nonlinear gain and a time delay. To linearize the dynamic behavior of this actuator for better actuating performance, a nonlinearity compensation method by a second-order polynomial was proposed. In the final step, the bending behavior of the constructed IPMC actuator with an open-loop and a closed-loop controller design was investigated. The results indicated that a low cost but reliable IPMC actuator was fabricated successfully. Its production time was less than half of current manufacturing time (more than 48 h). The bending motion at low operation frequencies was well controlled by a conventional PID controller without adding complicated control algorithm. Our proposed algorithm decreased the maximum overshot from 30 to 4.2%, and the steady-state error from 15 to 4%. Though the rise time was increased from 0.084 to 0.325 s, it was within the limit for many biomedical applications.

Piezoelectric force sensing

Abstract: A system and method for measuring absolute pressure applied to a piezoelectric element by measuring a transition time of a voltage pulse applied to a piezoelectric element. The transition time (such as the rise time and/or fall time of the voltage pulse) is affected by the capacitance of the piezoelectric element, which in turn is affected by the amount of pressure currently being applied to the piezoelectric element. The system may also provide haptic feedback via the same piezoelectric element.

Hydrogen Sensor Based on Palladium Coated Side-Polished Single-Mode Fiber

Abstract: This paper reports a fiber-optic hydrogen sensor based on a side-polished single-mode fiber coated with a palladium (Pd) thin film whose optical characteristics change as it absorbs hydrogen. The optical transmission loss of the sensor depends on the hydrogen gas concentration through the complex electric permittivity of the Pd film. An optimal design for the sensor has been pursued to obtain both high sensitivity and short response time. When exposed to 4% hydrogen gas, the optimal change output power obtained in this experiment was 1.2 dB (32%) with a rise time of 100 s.

Compact Subnanosecond Pulse Generator Using Avalanche Transistors for Cell Electroperturbation Studies

Abstract: Research on the electroperturbation effects of ultrashort high field pulses in cancer cells requires subnanosecond rise time, high voltage pulses delivered to low impedance biological loads Here we present a compact solid-state pulse generator developed for this application The pulse is generated by switching a chain of avalanche transistors configured as a tapered transmission line from high voltage to ground The system features a built in 1400:1 capacitively compensated resistive voltage divider The divider, with a 3 dB point at 910 MHz, overcomes challenges in the direct measurement of the high frequency components of the output pulse The generator is capable of producing a 08 ns rise time, 13 ns wide, 11 kV pulse into a 50 Omega load at a maximum repetition rate of 200 kHz Techniques to implement physical layouting strategies to achieve subnanosecond rise times are outlined Problems faced in integrating the subnanosecond pulse generator with a biological load are discussed This pulse generator will be used in experiments aimed at electromanipulation of intracellular biomolecular structures

A Fixed-Angle Heat Spreading Model for Dynamic Thermal Characterization of Rear-Cooled Substrates

Abstract: During a period of almost 40 years already, various fixed-angle heat spreading models have been developed in the literature. These models can be used by thermal engineers as approximations for the thermal steady state resistance of a heat source on a rear-cooled substrate. In this paper an extension of these models to dynamic (time-dependent) phenomena is proposed. The heat dissipated by a square source (side a) is assumed to spread out into the substrate (thickness ts) under a fixed angle Phi. An analytical solution for the complex thermal impedance Zth(jomega) in phasor notation is derived. The obtained expression, in which Phi is used as a fitting parameter, is compared with exact results. A very good agreement is observed (average relative error less than 6%) for a wide range of the normalized thickness lambda = ts/a. A compact expression for the optimal heat spreading angle as a function of lambda is given. Finally the temperature response to a heat power step is investigated. A simple formula for the thermal rise time is provided, allowing a thermal designer to make quick yet accurate estimations about the dynamic behavior of the device.

Harmful voltage overshoots due to turn-on behaviour of ESD protections during fast transients

Abstract: Due to the reaction time of the devices, the rise time of an ESD pulse has a strong effect on the efficiency of a protection network. (vf-)TLP clearly causes different failure modes depending on the rise time. This knowledge is needed to design protections that can handle fast ESD transients.

Determination of gas pressure in vacuum interrupter based on partial discharge

Abstract: Partial discharge characteristics in air under a low vacuum region were studied to develop a diagnosis technique to determine the gas pressure in a vacuum interrupter. The pressures were set at from 1.3 Pa to 2.6 kPa in order to simulate the leakage of gas into the vacuum interrupter. The structure of the vacuum interrupter, the measurement and the circuit construction for the experimental setup were described. The measurement of partial discharge occurring inside the vacuum interrupter was performed with a current transformer, intensified charge coupled device (1CCD) camera and photomultiplier tube. The measurement of partial discharge light intensity with a photomultiplier tube was more sensitive compared with that measured with a current transformer. From this result, an attempt has been made to distinguish the pressure below and above 260 Pa on the basis of the rise time and peak intensity of discharge light pulses. A relatively longer rise time (2 mus) with a smaller magnitude (less than 0.5 mA) was attributed to a Townsend-like discharge at pressures below 260 Pa, while a sharper rise time ~(10-100 ns) with a larger magnitude (greater than 1 mA) was characterized as a streamer-like discharge above 260 Pa. In addition, the estimation of gas pressure in a vacuum interrupter was made based on phase-resolved discharge characteristics utilizing an artificial neural network.

Data acquisition with a fast digitizer for large volume HPGe detectors

Abstract: A 12-bits and 420 MSample/s waveform digitizer was used with large volume High Purity Germanium (HPGe) detectors for measurements of gamma-ray production cross-section from inelastic neutron scattering. For these time-of-flight measurements at the GELINA white neutron source, the use of a fast digitizer significantly increases the efficiency compared with a conventional data acquisition system. First, the pulse processing time required to obtain the amplitude with high resolution is significantly reduced so that pulse pile-up with the prompt gamma-burst is eliminated for neutron-induced events. Second, an improved time response is obtained for which the amplitude and rise time dependence is strongly reduced compared to that of a conventional constant fraction discriminator. Excellent energy and time resolution is obtained with algorithms suitable for on-line signal processing, so that data storage is under control. Bench tests are presented that compare methods of signal processing. For the best method, the data acquisition system based on the fast digitizer was tested during measurements of gamma production cross-sections for Pb 206 and Pb 208 . A direct comparison was made with results obtained with conventional electronics operated in parallel.

A High-Speed Low-Noise 16-Channel CSA With Automatic Leakage Compensation In 0.35- $\mu$ m CMOS Process for APD-Based PET Detectors

Abstract: Design, implementation, analysis and measured performance results of a new high-speed low-noise 16-channel charge-sensitive preamplifier (CSA) prototype with automatic detector leakage compensation are presented. The prototype has been fabricated in TSMC 0.35-mum CMOS process and is designed for use with avalanche photodiode (APD) based PET detectors. The CSA is used to read out charge signals from a 4times4 APD array having 3 pF of capacitance and 75 nA of leakage current per pixel. A single channel CSA has 16 gain settings measured to range from 31.7 mV/fC to 4.5 mV/fC. The gain settings for all channels are set by a 64-bit on-chip shift register. The signal rise time at the CSA output was measured to be as fast as 2.9 ns (5%-55% rise time) and 4.8 ns (20%-80% rise time). A feedback MOS transistor biased in the triode region is used to reset the CSA output and a very slow Gm-feedback loop performs automatic leakage compensation up to 10 muA of leakage current per channel. Minimum input referred rms noise of 350 e- was measured with a pure capacitive input load and 1200 e- with an actual APD load biased at -1.7 kV connected to the CSA input, both at 0.1-mus peaking time. The prototype chip draws less than 50 mA of total current from a +3.3 V supply.

Effects of pulsed-excitation applied voltage rise time on argon metastable production efficiency in a high pressure dielectric barrier discharge

Abstract: The authors have quantified the effect of pressure scaling on Ar metastable production efficiency in a dielectric barrier discharge with and without dielectric component losses. Estimates of the volume averaged deposited energy were performed for both short or long rise time voltage pulses, using the same total applied voltages of ∼10 and ∼150ns, respectively. The metastable production efficiencies of long-pulse discharge exhibit smaller decrease over the 100–500Torr pressure range, compared to those of the short-pulse one to the extent that the efficiency values and scaling for both cases are essentially the same within the experimental uncertainty.

Electrodeposited submicron thermocouples with microsecond response times.

Abstract: We describe a procedure for preparing submicron scale silver−nickel thermocouples (TCs) using electrochemical step edge decoration on graphite surfaces. Each fabrication operation produced ensembles of 2−20 TCs with diameters in the 1.0 μm to 500 nm range. These “sub-μm TCs” (SMTCs) produced linear voltage versus temperature output over the range from 20 to 100 °C characterized by a Seebeck coefficient of 20 ± 1 μV/°C, equal to the 21 μV/°C that is theoretically expected for a junction between these two metals. The time response of SMTCs was evaluated using two different laser-heating methods and compared with the smallest mechanically robust commercially available type J TCs. Electrochemical etching of the silver wire introduced constrictions at grain boundaries that reduced the thermal mass of the junction without altering its integrity or its overall diameter, producing a decrease of the measured rise time for SMTCs up to 96%.

Switching characteristics of microplasmas in a planar electrode gap

Abstract: Microplasmas at high pressure have been the authors’ special interest for its practical relevance to the development of a switch. They concentrated on repetitive switching with a possibility to exceed the up to now known values for plasma closing switches and simultaneously maintaining a subnanosecond rise time of the switched pulses at a load. They examined several parameters for this purpose such as the electrode gap spacing, the electrode geometry, the gas type, the gas pressure, and including the applied voltage and current rating to operate these plasmas.

Development of a 3 ns rise and fall time strip-line kicker for the International Linear Collider

Abstract: The kicker systems for the damping rings (DR) of the International Linear Collider (ILC) assume the use of multiple units of strip-line electrodes and fast pulse power supplies for beam injection and extraction. The design of the DR with a 6.7 km circumference requires the kicker system to have a 3 ns (or 6 ns) rise and fall time and a 6 MHz (or 3 MHz) repetition rate. The development of a single unit of a kicker system having such a performance was carried out at KEK-ATF DR. A system to improve the rise and fall time of the kick field by combining two opposite-sign pulses was developed. A rise time for the kick field of less than 3 ns is achieved using this technique.

Energy Efficiency of Corona Discharge Reactor Driven by Inductive Energy Storage System Pulsed Power Generator

Abstract: Characteristics of a pulse corona reactor driven by an inductive energy storage (IES) pulsed power generator are described in this paper with focusing on the influence of streamer-to-glow transition on NO removal efficiency. A pulsed high voltage with a short rise time of under 30 ns is employed to generate streamer discharges homogeneously in whole the discharge region. Fast recovery diodes are used as semiconductor opening switch (SOS) to shorten the rise time. The various resistors are employed as dummy load to clarify a suitable circuit parameter such as the capacitance of a primary energy storage capacitor and/or the inductance of a secondary energy storage inductor. The energy transfer efficiency of the pulsed power generator has a maximum value of 50% at 714 Omega dummy load resistance. A co-axial cylinder type discharge chamber was used as the corona discharge plasma reactor driven by the IES pulsed power generator. The pulsed power generator supplies 30 kV pulse with 300 pps repetition rate. The co-axial cylinder plasma reactor consists of 1 mm diameter tungsten wire and 19 mm i.d. copper tube with 30 cm length. NO removal from the simulated diesel engine exhaust gas (N2:O2=9:1, Initial NO concentration=200 ppm) increased with input energy into the reactor. The energy efficiency for NO removal was obtained to be 25 g/kWh at 30 % removal in gas flow rate of 2 L/min. However, the energy efficiency decreased to 5 g/kWh with increasing capacitance of the primary capacitor from several hundreds pF to several nF. This decrease was caused by a streamer-to-glow transition. The efficiency was affected by oxygen concentration in the gas mixture.

Closed-Form RC and RLC Delay Models Considering Input Rise Time

Abstract: The Elmore delay model is the most popular and efficient delay model used for analytical delay estimation. Closed-form delay formulas are useful for circuit design, timing-driven physical design, synthesis, and optimization. As signal rise time becomes faster and the line resistance becomes smaller from copper technology, the significance of inductance increases. Both RC and RLC delays are a strong function of signal rise time. We propose a novel and efficient delay modeling method based on nondimensionalization to consider finite input rise time as an improvement over the Elmore's approach. To further improve the accuracy of the delay model, a new correction method, effective distance correction factor (EDCF), is proposed to consider resistive shielding of downstream capacitance. EDCF can be used to correct the delays for both RC and RLC tree structures. The proposed delay modeling method was applied to a number of nets selected from an integrated circuit (IC) design, and the delay estimation results were compared with HSPICE simulations. The new delay model retains the efficiency and simplicity of the Elmore delay model with significantly improved accuracy.

X-ray radiation from the volume discharge in atmospheric-pressure air

Abstract: X-ray radiation from the volume discharge in atmospheric-pressure air is studied under the conditions when the voltage pulse rise time varies from 0.5 to 100 ns and the open-circuit voltage amplitude of the generator varies from 20 to 750 kV. It is shown that a volume discharge from a needle-like cathode forms at a relatively wide voltage pulse (to ≈60 ns in this work). The volume character of the discharge is due to preionization by fast electrons, which arise when the electric field concentrates at the cathode and in the discharge gap. As the voltage pulse rise time grows, X-ray radiation comes largely from the discharge gap in accordance with previous experiments. Propagation of fast avalanche electrons in nitrogen subjected to a nonuniform unsteady electric field is simulated. It is demonstrated that the amount of hard X-ray photons grows not only with increasing voltage amplitude but also with shortening pulse rise time.

Voltage level shifter

Abstract: A high-speed, area-efficient level shifter includes transistors having a variety of oxide thicknesses. The level shifter has a protection circuit stage, and a current mirror stage that allows the level shifter to perform over a wide voltage range at a high frequency. The level shifter maintains rise time, fall time, and duty cycle over a wide range of input and output voltage levels.

A high-power semiconductor switch of high-voltage pulses with a rise time of nanosecond duration

Abstract: The results of studies of new fast-acting semiconductor devices—deep-level dynistors intended for use in high-power devices of nano-and microsecond pulsed-power technology—are presented. The possibility of switching multikiloampere current pulses having a rise rate of 200 kA/μs with the use of a single device with a 12-mm-diameter structure is shown. A high-power switch based on an assembly of dynistors with an operating voltage of 12 kV connected in series is described. The switch is capable of switching current pulses with a 1200-A amplitude and a 4-ns rise time.

Arrays of Addressable Microcavity Plasma Devices

Abstract: Addressable microcavity plasma devices with two- or three-electrode, dielectric barrier designs have been fabricated in 20 times 20 or 50 times 50 device arrays in Si(100) and characterized in the rare gases. Each device comprises a metal/Si electrode structure, a dielectric stack, and an inverted square pyramid microcavity having an emitting aperture of 50times50 mum2 or 100times100 mum2. Arrays with filling factors of 11% and 25% [for (100 mum)2 and (50 mum)2 device arrays, respectively] and a crossed electrode (passive matrix) geometry exhibit operating voltages in Ne of ~220-300 V (RMS) when driven by a 20-kHz sinusoidal driving voltage. Displacement currents are ~50% of those for previous Si microplasma device arrays, and when exciting the array with 100-140-V pulses, the rise time of the wavelength-integrated fluorescence is observed to be < 600 ns for pure Ne or Ne/5%Xe gas mixtures at a pressure of 700 torr. A full address and sustain pulse sequence has also been demonstrated with a symmetrical three-electrode device structure

Methods of generating plasma, of etching an organic material film, of generating minus ions, of oxidation and nitriding

Abstract: A direct current pulse voltage is applied on a treatment gas to generate a discharge plasma. The duty ratio of the direct current pulse voltage is controlled within the range of 0.0001% or more and 8.0% or less. The rise time of the direct current pulse voltage is controlled in the range of not lower than 0.1 V/nsec and not higher than 10000 V/nsec. Alternatively, a positive pulse and a negative pulse are applied from a single power source for performing the discharge plasma and the impurity implantation.

A discussion on exponential-gain charge pump

Abstract: This paper presents a discussion about the performance achievable by an exponential-gain charge pump (i.e., by a charge pump featuring a voltage gain which increases exponentially with the number of stages). This charge pump topology is analyzed in terms of both voltage gain and equivalent output resistance. An analytical expression of these two parameters is provided, which allows performance comparison with other charge pump topologies. The expression of the output voltage rise time is also derived.

Low-Power BiCMOS Optical Receiver With Voltage-Controlled Transimpedance

Abstract: An optical receiver with voltage-controlled transimpedance using a current conveyor and a voltage amplifier monolithically integrated with a PIN photodiode in 0.6 mum BiCMOS technology is presented. The transimpedance is directly proportional to a voltage-controlled resistance, and can be continuously varied by changing its control voltage. Thanks to the mixed current-mode and voltage-mode signal processing, the bandwidth of the optical receiver is virtually independent of the photodiode capacitance. A linearity error smaller than 3.1%, a sensitivity dynamic range of 78.8 (37.9 dB) with the largest sensitivity of S = 890 mV/muW at 660 nm, an offset voltage smaller than 0.53 mV, a largest maximum power consumption of only 3.2 mW, a small-signal frequency bandwidth up to 189 MHz, a large-signal rise time/fall time down to 3.7 ns/3.3 ns, and an output noise level down to -77.8 dBm (for a frequency of 50 MHz and a resolution bandwidth of 30 kHz) are achieved.

Experimental Study of Perpendicular Write Head Field Rise Time

Abstract: In this paper, a simple technique that can determine the write head field rise time based on electrical measurements is presented. A model that relates the head electrical properties to the frequency dependent head efficiency epsiv(omega) and head field rise time tau is described in detail. This method only requires knowledge of the complex impedances of a magnetically saturated head and an unsaturated head. The results obtained are verified with recording measurements of the rise time for the same heads. Very good agreement was found for all heads. It was also found that the presence of a soft underlayer does not seem to significantly affect the measured head field rise time. Therefore, it is concluded that the head field rise time is determined by the yoke structure and not by the pole tip area

Microwave High-Speed Liquid Crystal Devices Using CPW with Floating Electrode

Abstract: We develop a transmission line with a floating electrode (FE) arranged on a coplanar waveguide (CPW), and we propose using this transmission line to reduce the decay time of a microwave-band liquid crystal loaded device. Using the proposed CPW-FE structure makes it possible to control both the rise time and decay time by varying the applied bias field, thereby allowing the decay time to be reduced. In the 18 GHz band variable phase shifter we developed, we obtained a rise time of 75 ms and a decay time of 200 ms with a 500 μm wide CPW center conductor, a gap of 20 μm between the center conductor and ground plane, and a liquid crystal layer thickness of 50 μm. Under these conditions, the birefringence Δϵ′ of the liquid crystal was 0.23.

Partial discharge inception characteristics by different measuring methods in magnet wire under surge voltage application

Abstract: We have been investigating the PD activities of magnet wire for inverter-fed motor under surge voltage application. In this paper, we obtained and compared PD inception characteristics by using different measuring methods and discussed PD generation mechanism in consideration of surface charging. PD signals were detected by electrical, optical and electromagnetic methods using high-frequency current transformer (CT) with balance circuit method, photo multiplier tube (PMT) and monopole antenna. Experimental results firstly revealed that PD inception voltage (PDIV) measured by PMT was the lowest, i.e., PMT exhibited the highest sensitivity for PD detection under surge voltage. Secondly, the surface charging on enameled wire caused by PD at the rise time of surge voltage could generate PD at the fall time of the surge voltage. Furthermore, according to the overshoot factor of surge voltage, generation probability of initial electrons and so on, PD could be generated not only at the rise time and fall time of the surge voltage, but also in the plateau duration.

The Validity of the Similarity Law for the Electrical Breakdown of $\hbox{SF}_{6}$ Gas

Abstract: The aim of this paper is to investigate the justification and the limitation of the geometrical similarity law application on the electrical breakdown of SF6 gas. For this purpose, the measurements of the dielectric breakdown voltage for similar systems insulated with SF6 gas were done. The applied dc voltage source had an 8 V/s rate of rise. Standard double exponential overvoltage pulse (rise time T1=1.2 mus, fall time T2 =50 mus) of the amplitude U1 max=320 V, U 2 max=4.80 kV, and U3 max=640 kV was used. On the basis of the obtained experimental results and theoretical considerations, the conditions under which the geometrical similarity laws are applicable on discharges in gases are determined. It was concluded that there is no correlation between the geometrical similarity of the electrode surface topography and corresponding breakdown voltages. It was shown that the extension of the similarity law, introducing the electron mean free path as a linear dimension of the system, gives a good quantitative agreement. Also, in case of the pulse breakdown voltage, it is necessary to apply the breakdown possibility rise law

Design and characterization of a high-power induction module at megahertz repetition rate burst mode

Abstract: The special design considerations for a unique high-power multiple-pulse induction module at megahertz repetition rate burst mode are presented and a prototype triple-pulse induction module has been constructed to verify the engineering feasibility of such a scheme. In the prototype module, three single pulses produced independently by three Marx-charged Blumlein pulse forming lines are isolated and merged by six high-voltage rectifier diodes. Experiments conducted with an iron-based metallic glass (1K101) test induction cell demonstrate that a train of three ∼250 kV pulses separated by 800 ns can be obtained in the induction gap of the cell without resetting the magnetic cores between pulses. A pulse with a rise time of 35 ns, ±1% flat top of 60 ns, and full-width at half-maximum of 120 ns was obtained when tested with a formal linear induction cell and finely tuned. It appears that nonlinear characterization of magnetic cores results in an increase in magnetization current and voltage drop pulse by pulse; the distortion of voltage waveform is not observed in the module if the voltage-seconds of the magnetic cores are sufficient. Because 1K101 metallic glass core has two times the equivalent flux swing of that of NiZn ferrite, metallic glass is advantageous for designing a compact multiple-pulse induction cell. The maximum amplitude of the voltage reversal is about 26% of that of the incident pulse when the cores are saturated.

Frequency converter, motor, motor drive system and maintenance method for motor drive system

Abstract: A frequency converter for outputting a power to drive a motor, having: an inverter unit for inverting a d.c. power to an a.c. power; a control unit for controlling the inverter unit; and a housing for supporting at least the inverter unit and control unit, wherein a rise time change unit is provided in the housing, the rise time change unit changes a rise time of a waveform of a voltage output from the inverter unit.